Dissertations / Theses: 'Solid-fluid interaction'

1

De, La Peña-Cortes Jesus Ernesto. "Development of fluid-solid interaction (FSI)." Thesis, University of Manchester, 2018. https://www.research.manchester.ac.uk/portal/en/theses/development-of-fluidsolid-interaction-fsi(b22b29e2-0349-44a9-ab18-eeb0717d18c8).html.

Full text

Abstract:

This work extends a previously developed finite-volume overset-grid fluid flow solver to enable the characterisation of rigid-body-fluid interaction problems. To this end, several essential components have been developed and blended together. The inherent time-dependent nature of fluid-solid interaction problems is captured through the laminar transient incompressible Navier-Stokes equations for the fluid, and the Euler-Newton equations for rigid-body motion. First and second order accurate time discretisation schemes have been implemented for the former, whereas second and third order accurate time discretisation schemes have been made available for the latter. Without doubt the main advantage the overset-grid method offers regarding moving entities is the avoidance of the time consuming grid regeneration step, and the resulting grid distortion that can often cause numerical stability problems in the solution of the flow equations. Instead, body movement is achieved by the relative motion of a body fitted grid over a suitable background mesh. In this case, the governing equations of fluid flow are formulated using a Lagrangian, Eulerian, or hybrid flow description via the Arbitrary Lagrangian-Eulerian method. This entails the need to guarantee that mesh motion shall not disturb the flow field. With this in mind, the space conservation law has been hard-coded. The compliance of the space conservation law has the added benefit of preventing spurious mass sources from appearing due to mesh deformation. In this work, two-way fluid-solid interaction problems are solved via a partitioned approach. Coupling is achieved by implementing a Picard iteration algorithm. This allows for flexible degree of coupling specificationby the user. Furthermore, if strong coupling is desired, three variants of interface under-relaxation can be chosen to mitigate stability issues and to accelerate convergence. These include fixed, or two variants of Aitkenâs adaptive under-relaxation factors. The software also allows to solve for one-way fluid-solid interaction problems in which the motion of the solid is prescribed. Verification of the core individual components of the software is carried out through the powerful method of manufactured solutions (MMS). This purely mathematically based exercise provides a picture of the order of accuracy of the implementation, and serves as a filter for coding errors which can be virtually impossible to detect by other means. Three instances of one-way fluid-solid interaction cases are compared with simulation results either from the literature, or from the OpenFOAM package. These include: flow within a piston cylinder assembly, flow induced by two oscillating cylinders, and flow induced by two rectangular plates exhibiting general planar motion. Three cases pertaining to the class of two-way fluid-interaction problems are presented. The flow generated by the free fall of a cylinder under the action of gravity is computed with the aid of an intermediate âmotion trackingâ grid. The solution is compared with the one obtained using a vorticity based particle solver for validation purposes. Transverse vortex induced vibrations (VIV) of a circular cylinder immersed in a fluid, and subject to a stream are compared with experimental data. Finally, the fluttering motion of a rectangular plate under different scenarios is analysed.

APA, Harvard, Vancouver, ISO, and other styles

2

Hester, Eric William. "Modelling fluid-solid interactions." Thesis, The University of Sydney, 2021. https://hdl.handle.net/2123/25114.

Full text

Abstract:

Fluid-solid interactions have wide-ranging implications for science, engineering, and the global climate. This thesis combines mathematical analysis, computational algorithms, and laboratory experiments to understand fluid-solid interactions, providing new insights on the influence of shape on iceberg melting, and mysterious boat drag in the dead-water effect. The discontinuous interfaces of fluid-solid interactions are challenging to simulate. We develop improved diffuse-domain methods that allow straightforward algorithms to simulate fluid-solid interactions. Diffuse-domain methods are simple to implement because they replace complicated boundary conditions with smooth source terms. But the smoothing induces a boundary layer of size ε between the fluid and solid. Previous diffuse-domain methods incurred errors of this size—corresponding to first order numerical accuracy. The first part of the thesis develops an asymptotic framework to derive second-order accurate diffuse-domain methods. In chapter 2, we exploit the signed distance function to simplify vector calculus around boundary layers in arbitrary smooth geometries. In chapter 3 we apply this machinery to optimise the volume-penalty method for fluid-solid interactions. In chapter 4 we then derive higher-order phase-field models for coupled melting, dissolution, and convection. We verify these corrections in extensive numerical benchmarks. We also explore techniques for fourth order convergence in ε using Richardson extrapolation, and spectral accuracy simulations via coordinate remapping. These improved methods provide powerful tools to simulate and understand real-world fluid-solid interactions. In chapter 5, we apply these methods to investigate how iceberg shape affects melting. Icebergs vary in shape and size, and iceberg melting determines their influence on the climate. Our laboratory experiments reveal previous models underestimate melting and ignore large differences between sides. The improved phase-field model reproduces experimental melt rates and explains observed patterns. Simulations show that non-uniform basal melt rates stem from upwelling during vortex generation. We outline the geophysical implications of our findings and discuss improvements to current melting parameterisations that account for iceberg geometry. Then in chapter 6, we use these techniques to examine the dead-water effect—extreme boat drag in density-stratified waters. Walfrid Ekman showed in 1904 that sub-surface internal waves cause dead water. Boats moving near the internal wave speed generate large internal waves which steal energy from the boat. We perform the first direct numerical simulation of dead water. In contrast to previous potential flow models, we find that vorticity generated throughout the domain plays an important role in the effect. The vorticity coalesces into large, previously unnoticed eddies. These robust eddies interfere with the boat-wave interaction, and may suggest new strategies to mitigate the effect.

APA, Harvard, Vancouver, ISO, and other styles

3

Obadia, Benjamin. "A multimaterial Eulerian approach for fluid-solid interaction." Thesis, Cranfield University, 2012. http://dspace.lib.cranfield.ac.uk/handle/1826/7270.

Full text

Abstract:

This thesis is devoted to understanding and modeling multimaterial interactions, and to develop accordingly a robust scheme taking into account the largest variety of those, with a particular interest in resolving solid/fluid configurations. This very general frame of studies can be tackled with numerous different approaches as several issues arise and need to be addressed before attempting any modelisation of these problems. A first questioning should be the frame of reference to be used for the materials considered. Eulerian shock-capturing schemes have advantages for modeling problems involving complex non-linear wave structures and large deformations. If originally reserved mostly to fluids components, recent work has focused on extending Eulerian schemes to other media such as solid dynamics, as long as the set of equations employed is written under a hyperbolic system of conservation laws. Another matter of interest when dealing with multiple immiscible materials it the necessity to include some means of tracking material boundaries within a numerical scheme. Interface tracking methods based on the use of level set functions are an attractive alternative for problems with sliding interfaces since it allows discontinuous velocity profiles at the material boundaries whilst employing fixed grids. However, its intrinsic lack of variables conservation needs to be circumvented by applying an appropriate fix near the interface, where cells might comprise multiple components. Another requirement is the ability to correctly predict the physical interaction at the interface between the materials. For that purpose, the Riemann problem corresponding to the interfacial conditions needs to be formulated and solved. This implies in turn the need of appropriate Riemann solvers; if they are largely available when the materials are identical (i.e. governed by the same set of equations), a specific Riemann solver will be developed to account for fluid/solid interaction. Eventually, these newly developed methods will be tested on a wide range of different multimaterial problems, involving several materials undergoing large deformations. The materials used, whether modelling fluid/fluid or solid/fluid interactions, will be tested using various initial conditions from both sides of the interface, to demonstrate the robustness of the solver and its flexibility. These testcases will be carried out in 1D, 2D and 3D frames, and compared to exact solutions or other numerical experiments conducted in previous studies.

APA, Harvard, Vancouver, ISO, and other styles

4

Khodabakhshi, Goodarz. "Computational modelling of fluid-porous solid interaction systems." Thesis, Loughborough University, 2007. https://dspace.lboro.ac.uk/2134/35182.

Full text

Abstract:

Deformation of a porous medium due to the pressure applied by an interacting fluid passing through it is a phenomenon which occurs in a number of applications such as filtration and membrane separation processes. Mathematical modelling of these systems using porous medium theory has proved to be beneficial in the design of experiments and equipments as well as gaining better insight about multi-physics phenomenon such as combined fluid flow and solid deformation regimes. In the present work the interaction of fluid and porous solid medium has been studied.

APA, Harvard, Vancouver, ISO, and other styles

5

Pan, Kai Ph D. Massachusetts Institute of Technology. "Simulating fluid-solid interaction using smoothed particle hydrodynamics method." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/109642.

Full text

Abstract:

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2017.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 97-102).
The fluid-solid interaction (FSI) is a challenging process for numerical models since it requires accounting for the interactions of deformable materials that are governed by different equations of state. It calls for the modeling of large deformation, geometrical discontinuity, material failure, including crack propagation, and the computation of flow induced loads on evolving fluid-solid interfaces. Using particle methods with no prescribed geometric linkages allows high deformations to be dealt with easily in cases where grid-based methods would introduce difficulties. Smoothed Particle Hydrodynamics (SPH) method is one of the oldest mesh-free methods, and it has gained popularity over the last decades to simulate initially fluids and more recently solids. This dissertation is focused on developing a general numerical modeling framework based on SPH to model the coupled problem, with application to wave impact on floating offshore structures, and the hydraulic fracturing of rocks induced by fluid pressure. An accurate estimate of forces exerted by waves on offshore structures is vital to assess potential risks to structural integrity. The dissertation first explores a weakly compressible SPH method to simulate the wave impact on rigid-body floating structures. Model predictions are validated against two sets of experimental data, namely the dam-break fluid impact on a fixed structure, and the wave induced motion of a floating cube. Following validation, this framework is applied to simulation of the mipact of large waves on an offshore structure. A new numerical technique is proposed for generating multi-modal and multi-directional sea waves with SPH. The waves are generated by moving the side boundaries of the fluid domain according to the sum of Fourier modes, each with its own direction, amplitude and wave frequency. By carefully selecting the amplitudes and the frequencies, the ensemble of wave modes can be chosen to satisfy a real sea wave spectrum. The method is used to simulate an extreme wave event, with generally good agreement between the simulated waves and the recorded real-life data. The second application is the modeling of hydro-fracture initiation and propagation in rocks. A new general SPH numerical coupling method is developed to model the interaction between fluids and solids, which includes non-linear deformation and dynamic fracture initiation and propagation. A Grady-Kipp damage model is employed to model the tensile failure of the solid and a Drucker-Prager plasticity model is used to predict material shear failures. These models are coupled together so that both shear and tensile failures can be simulated within the same scheme. Fluid and solid are treated as a single system for the entire domain, and are computed using the same stress representation within a uniform SPH framework. Two new stress coupling approaches are proposed to maintain the stress continuity at the fluid-solid interface, namely, a continuum approach and stress-boundary-condition approach. A corrected form of the density continuity equation is implemented to handle the density discontinuity of the two phases at the interface. The method is validated against analytic solutions for a hydrostatic problem and for a pressurized borehole in the presence of in-situ stresses. The simulation of hydro-fracture initiation and propagation in the presence of in-situ stresses is also presented. Good results demonstrate that SPH has the potential to accurately simulate the hydraulic-fracturing phenomenon in rocks.
by Kai Pan.
Ph. D.

APA, Harvard, Vancouver, ISO, and other styles

6

Mohd, Razip Wee Farhan. "Solid-fluid interaction in a pillar based phononic crystal." Thesis, Bourgogne Franche-Comté, 2017. http://www.theses.fr/2017UBFCD055.

Full text

Abstract:

Les cristaux phononiques (CP) sont des structures constituées de motifs élémentaires périodisés qui sont conçus et dimensionnés de manière à obtenir une propagation d’ondes acoustiques ou élastiques très différente de la propagation naturelle dans un matériau non structuré. C’est un moyen très efficace pour façonner la propagation des ondes acoustiques grâce notamment à la présence de bandes interdites liées à la périodicité des motifs élémentaires ou liées à leurs résonances intrinsèques. Ces mécanismes de contrôle de la propagation d’ondes constituent un énorme potentiel technologique dans diverses applications (filtre, multiplexeur, guide d’onde, résonateur et capteur). De nombreux travaux ont permis le développement de dispositifs à ondes acoustiques de surface (SAW) intégrant des CP pour le contrôle d’ondes à haute fréquence. Néanmoins, de tels dispositifs devant fonctionner en présence d’un liquide en contact avec le CP présentent des difficultés de conception liées à l’affaiblissement des ondes à l’interface solide-fluide à cause de la radiation vers le fluide des ondes à composantes hors plan. Dans le cas particulier d’un usage au titre d’un capteur, les performances d’un tel dispositif sont souvent insuffisantes.L’objectif de l’étude menée dans le cadre de cette thèse est de remédier à ce problème en utilisant les résonances localisées de cristaux phononiques constitués de piliers pour concevoir des dispositifs opérationnels en milieu liquide.Dans un premier temps, des outils numériques basés sur la méthode des éléments finis ont été développés et validés pour la modélisation de cellules élémentaires d’un CP à base de piliers. Cela nous a permis de démontrer que la présence de résonances localisées de piliers judicieusement dimensionnés permet de ralentir la vitesse de l’onde Scholte-Stoneley à l’interface solide-fluide. Les modèles de dispositifs à base de CP ont été implémentés et utilisés pour valider les résultats retenus du modèle unitaire, dans un deuxième temps. Quant à la partie expérimentale, elle nous a permis de valider la persistance en milieu liquide des bandes interdites à résonances localisées qui est attribuée au fait qu’à la résonance des piliers, l’énergie reste confinée dans ces derniers empêchant ainsi sa radiation dans le fluide. Ces résultats nous ont permis de concevoir des guides d’ondes persistantes en milieu liquide par l’intégration au sein du CP de défauts géométriques sous forme d’une chaine de piliers ayant des dimensions différentes du reste des piliers du CP.L’étude théorique a montré que les ondes guidées que l'on peut engendrer en utilisant les deux types de bandes interdites (Bragg et résonances localisées) ont des propriétés proches d’une onde de surface de Rayleigh. Les résultats obtenus dans ce travail ont permis d’élucider et d'expliciter les mécanismes à l’origine de la persistance des modes propagatifs dans les CP à résonances localisées. Cela devrait permettre d'ouvrir un champ d’investigation visant à développer des capteurs SAW phononiques pour des applications en micro-fluidique, notamment des dispositifs de type lab-on-chip
Phononic crystal(PC) can be defined as an artificial structure built from periodical unit cell which could achieve interesting acoustic and elastic propagation thanks to the presence of phononic bandgap(PnBg) related to the periodicity and its intrinsic resonance of the unit cell. These mechanisms to control the wave’s propagation illustrate a huge potential that could led to several promising applications (filtering, waveguiding, resonator and sensor). Many works proposed the integration of surface acoustic wave(SAW) with PC with the purpose to manipulate the wave’s propagation at high frequency(UHF-VHF range). Nevertheless, the presence of liquid on the surface of such device induces an attenuation of the wave at the interface of solid-fluid due to the out-of-plane displacement which radiate into the fluid. For the development of such device as a sensor, its performance is usually degraded and not sufficient compared to the current state of art. The objective of this thesis is to provide a solution to the above problem through the utilization of locally-resonant mechanism in PC composed of an array of pillars to design a device which could operate in the liquid environment. First, we developed a theoretical model based on Finite Element Method (FEM) simulation for a unit cell of pillar-based structure embedded with a liquid medium. We demonstrated that local resonances of pillars with optimized dimension could decrease the phase velocity of Scholte-Stoneley wave, to produce a slow wave at the solid/fluid interface. For the experimental part, we showed the conservation of locally-resonant bandgap when the fabricated device is loaded with liquid. This conservation is attributed to the local resonance of pillars that confine the energy inside the pillar to prevent radiation of energy into the fluid. The obtained results allow us to design a waveguide persistent under liquid medium by the integration of geometrical defect in the PC in the form of a chain of pillars with a different dimension compared to the rest. Furthermore, the theoretical studies indicated also that the waveguide induced in the both type of band gap(Bragg and locally-resonant) has a close appearance as a Rayleigh SAW. The results from this study could elucidate the mechanism of the persistence of the propagation mode of locally-resonant PC. This could open a new perspective for a further investigation to develop SAW phononic especially in the in a microfluidic and lab on chip application

APA, Harvard, Vancouver, ISO, and other styles

7

Gobal, Koorosh. "High-Fidelity Multidisciplinary Sensitivity Analysis for Coupled Fluid-Solid Interaction Design." Wright State University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=wright1483614152174005.

Full text

APA, Harvard, Vancouver, ISO, and other styles

8

Behera, Narayana. "On the solutions of fluid flow and solid deformation interaction problems /." The Ohio State University, 1992. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487777901658103.

Full text

APA, Harvard, Vancouver, ISO, and other styles

9

Hajishafiee, Alireza. "Finite-volume CFD modelling of fluid-solid interaction in EHL contacts." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/32100.

Full text

Abstract:

Classically in an elastohydrodynamic (EHD) problem, the Reynolds equation is the most widely used PDE to describe the behaviour of lubricants in high-pressure non-conforming contacts, and elastic deformation is usually calculated using the Hertzian theory of elastic contacts. This thesis outlines the development of a new method for modelling of fluid-solid interactions in elastohydrodynamic lubrication (EHL) contact based on Finite Volume (FV) techniques. A Computational Fluid Dynamics (CFD) approach to solve the Navier-Stokes equations is implemented to model lubrication in roller bearings using the open-source package OpenFOAM. This has first been applied to simulate full film hydrodynamic lubrication (HL), enabling an accurate description of the flow within the entire domain surrounding the contact region. The rheology is assumed to be non-Newtonian and shear-thinning. The phenomenon of cavitation is modelled by implementing a homogenous equilibrium cavitation model, which maintains specified lubricant saturation pressure in cavitating region. The current fluid solver involves the solution of the full momentum and energy equations, and satisfying continuity. The aim is firstly to demonstrate the range of applicability and the limitations of traditional formulations of the Reynolds equation and secondly to highlight areas where Navier-Stokes based approaches are necessary for accurate solution of lubrication problems. Subsequently, a finite volume solid solver is fully coupled with the fluid solver in a forward iterative manner to take into account elastic deflection effects using Navier-Lamé equation. The advantage of using a single numerical tool enables an internal transfer of information at the fluid-solid interface through one common data structure. The stability of the model, in the presence of high contact pressures, is enhanced by incorporation of multigrid method, implicit coupling and improved mesh adaption and motion techniques. The developed model has been applied to a series of lubricated metal on metal smooth line contact with slide to roll ratios ranging from 0 to 2 and is stable for a wide range of industrial operating conditions (pressures up to 4 GPa). The model is further improved to account for time-dependent transient behaviour of an EHL rough contact. The results for a travelling ridge, dent and sinusoidal wave through EHL conjunction are presented.

APA, Harvard, Vancouver, ISO, and other styles

10

Franci, Alessandro. "Unified Lagrangian formulation for fluid and solid mechanics, fluid-structure interaction and coupled thermal problems using the PFEM." Doctoral thesis, Universitat Politècnica de Catalunya, 2015. http://hdl.handle.net/10803/291562.

Full text

Abstract:

The objective of this thesis is the derivation and implementation of a unified Finite Element formulation for the solution of uid and solid mechanics, Fluid-Structure Interaction (FSI) and coupled thermal problems. The unified procedure is based on a stabilized velocity-pressure Lagrangian formulation. Each time step increment is solved using a two-step Gauss-Seidel scheme: first the linear momentum equations are solved for the velocity increments, next the continuity equation is solved for the pressure in the updated configuration. The Particle Finite Element Method (PFEM) is used for the fluid domains, while the Finite Element Method (FEM) is employed for the solid ones. As a consequence, the domain is remeshed only in the parts occupied by the fluid. Linear shape functions are used for both the velocity and the pressure fields. In order to deal with the incompressibility of the materials, the formulation has been stabilized using an updated version of the Finite Calculus (FIC) method. The procedure has been derived for quasi-incompressible Newtonian fluids. In this work, the FIC stabilization procedure has been extended also to the analysis of quasi-incompressible hypoelastic solids. Specific attention has been given to the study of free surface flow problems. In particular, the mass preservation feature of the PFEM-FIC stabilized procedure has been deeply studied with the help of several numerical examples. Furthermore, the conditioning of the problem has been analyzed in detail describing the effect of the bulk modulus on the numerical scheme. A strategy based on the use of a pseudo bulk modulus for improving the conditioning of the linear system is also presented. The unified formulation has been validated by comparing its numerical results to experimental tests and other numerical solutions for fluid and solid mechanics, and FSI problems. The convergence of the scheme has been also analyzed for most of the problems presented. The unified formulation has been coupled with the heat tranfer problem using a staggered scheme. A simple algorithm for simulating phase change problems is also described. The numerical solution of several FSI problems involving the temperature is given. The thermal coupled scheme has been used successfully for the solution of an industrial problem. The objective of study was to analyze the damage of a nuclear power plant pressure vessel induced by a high viscous fluid at high temperature, the corium. The numerical study of this industrial problem has been included in the thesis.
El objectivo de la presente tesis es la derivación e implementación de una formulación unificada con elementos finitos para la solución de problemas de mecánica de fluidos y de sólidos, interacción fluido-estructura (Fluid-Structure Interaction (FSI)) y con acoplamiento térmico. El método unificado està basado en una formulación Lagrangiana estabilizada y las variables incognitas son las velocidades y la presión. Cada paso de tiempo se soluciona a través de un esquema de dos pasos de tipo Gauss-Seidel. Primero se resuelven las ecuaciones de momento lineal por los incrementos de velocidad, luego se calculan las presiones en la configuración actualizada usando la ecuación de continuidad. Para los dominios fluidos se utiliza el método de elementos finitos de partículas (Particle Finite Element Method (PFEM)) mientras que los sólidos se solucionan con el método de elementos finitos (Finite Element Method (FEM)). Por lo tanto, se ramalla sólo las partes del dominio ocupadas por el fluido. Los campos de velocidad y presión se interpolan con funciones de forma lineales. Para poder analizar materiales incompresibles, la formulación ha sido estabilizada con una nueva versión del método Finite Calculus (FIC). La técnica de estabilización ha sido derivada para fluidos Newtonianos casi-incompresibles. En este trabajo, la estabilización con FIC se usa también para el análisis de sólidos hipoelásticos casi-incompresibles. En la tesis se dedica particular atención al estudio de flujo con superficie libre. En particular, se analiza en profundidad el tema de las pérdidas de masa y se muestra con varios ejemplos numéricos la capacidad del método de garantizar la conservación de masa en problemas de flujos en supeficie libre. Además se estudia con detalle el condicionamiento del esquema numérico analizando particularmente el efecto del módulo de compresibilidad. Se presenta también una estrategia basada en el uso de un pseudo módulo de compresibilidad para mejorar el condicionamiento del problema. La formulación unificada ha sido validada comparando sus resultados numéricos con pruebas de laboratorio y resultados numéricos de otras formulaciones. En la mayoría de los ejemplos también se ha estudiado la convergencia del método. En la tesis también se describe una estrategia segregada para el acoplamiento de la formulación unificada con el problema de transmisión de calor. Además se presenta una simple estrategia para simular el cambio de fase. El esquema acoplado ha sido utilizado para resolver varios problemas de FSI donde se incluye la temperatura y su efecto. El esquema acoplado con el problema térmico ha sido utilizado con éxito para resolver un problema industrial. El objetivo del estudio era la simulación del daño y la fusión de la vasija de un reactor nuclear provocados por el contacto con un fluido altamente viscoso y a gran temperatura. En la tesis se describe con detalle el estudio numérico realizado para esta aplicación industrial

APA, Harvard, Vancouver, ISO, and other styles

11

Chen, Zipeng. "A Smoothed Particle Hydrodynamics Approach for Modelling Meso-scale Fluid–Fracture Interaction." Thesis, The University of Sydney, 2021. https://hdl.handle.net/2123/28188.

Full text

Abstract:

The fluid–fracture interaction at meso-scale is vital in numerous applications and challenging for numerical studies. During this process, the solid deforms or even damages due to the force transmitted from the surrounding fluid, whereas the deformation and failure of the solid in turn change the flow behaviour. Besides, the surface tension and wettability at meso-scale can have considerable effects on fluid behaviour. As a particle-based approach, the smoothed particle hydrodynamics (SPH) has shown its capability in modelling the flow at multiscale and potential in reproducing the fracture. Therefore, to model the fluid–fracture interaction at meso-scale, this thesis aims to develop a modified SPH method considering the surface tension of fluid and the fracture propagation of solids at meso-scale. In this approach, an interparticle force that can provide repulsive force in a short-range and attractive force in a long-range is introduced to model the fluid–fluid and fluid–solid interactions. Compared to traditional methods modelling the surface tension and wettability, the proposed interparticle force can be employed in complex geometry without explicitly identifying the fluid–solid interface. The formation of a droplet with surface tension and the change of contact angles on fluid–solid interface demonstrate the capability in reproducing the mesoscopic effects. Moreover, this interparticle force can prevent the SPH particles from clustering when under great pressure. The compressibility of the pipe flow is consistent with the physical value of water without particle clustering. This interparticle force is then coupled with the no-slip boundary to expand its application range. The simulation results of the Couette flow and the Poiseuille flow are consistent with the analytical solution, showing the feasibility of using this approach in the pipe flow under a no-slip boundary. For the solid part, the Drucker–Prager (DP) model and the Grady–Kipp (GK) damage model are combined and implemented to describe the shear failure and tensile failure, respectively. A shear analytical model a biaxial compressive model and a uniaxial compressive experiment are simulated. The results show that the implemented DP model reproduces the shear failure well. After calibrating the GK damage model through the available uniaxial tensile test, the DP model is combined with the GK damage model. A Brazilian disc test is then simulated. The numerical results reproduce the fracture patterns consistent with the experimental ones, showing the feasibility of using this mixed solid model to express the complex fracture of rock-like material. Finally, by coupling the fluid model and the solid model, an SPH framework is formed to consider the surface tension and fracture of the solid. A process of hydraulic fracturing is simulated at the meso-scale with different in-situ stress conditions. Moreover, a pre-existing flaw is added in the solid domain to investigate the influence of natural fracture in hydraulic fracturing. The results suggest that tensile failure is the dominant failure type controlling the fracture pattern of hydraulic fracturing. Moreover, since the in-situ stress state and the pre-existing flaw have mutual effects, the hydraulic fracturing should be analysed comprehensively. All the results prove that this modified SPH method had considerable potential in modelling the fluid–fracture interaction with the consideration of the surface tension effects of fluid and the fracture propagation of solid.

APA, Harvard, Vancouver, ISO, and other styles

12

Kahl, Philipp. "Identification of long-range solid-like correlations in liquids and role of the interaction fluid-substrate." Thesis, Le Mans, 2016. http://www.theses.fr/2016LEMA1002/document.

Full text

Abstract:

Les liquides diffèrent des solides par une réponse retardée à la sollicitation en cisaillement; c’est-à-dire une absence d’élasticité de cisaillement et un comportement d'écoulement à basses fréquences (<1 Hz). Ce postulat pourrait ne pas être vrai à toutes échelles. A l’échelle submillimétrique, les mesures viscoélastiques (VE) réalisées en améliorant l'interaction entre le liquide et le substrat, montrent qu’une élasticité basses-fréquences existe dans des liquides aussi variés que les polymères, les surfondus, les liquides à liaison H, ioniques ou van der Waals. Ce résultat implique que les molécules à l'état liquide ne seraient pas dynamiquement libres, mais élastiquement corrélées.En utilisant les propriétés biréfringentes des fluctuations prétransitionnelles qui coexistent dans la phase isotrope des cristaux liquides, nous montrons qu'il est possible de visualiser ces corrélations « cachées ». Dans des conditionssimilaires aux mesures VE, une biréfringence optique synchrone à la déformation est observée dans la phase isotrope à des fréquences aussi basses que 0.01 Hz et des températures éloignées de toute transition. Le comportement dela biréfringence basses-fréquences a des similitudes avec l'élasticité; elle est en phase avec la déformation à faibles amplitudes de déformation, puis en phase avec le taux de déformation à plus grandes amplitudes. La biréfringence basses- fréquences est forte, sans défaut et réversible. Elle indique un ordre à longue portée. La synchronisation de la réponse à la sollicitation en fréquence et l’état ordonné qu’elle produit ne sont pas compatibles avec un état liquide isotrope mais montrent qu’il s’agit d’un état élastique soumis à déformation (entropie élastique)
Liquids differ from solids by a delayed response to a shear mechanical solicitation; i.e. they have no shearelasticity and exhibit a flow behaviour at low frequency (<1 Hz). This postulate might be not verified at thesub-millimeter scale. By optimizing the measurement in particular by improving the liquid/substrate interactions (wetting), a low frequency shear elasticity has been found in liquids including molten polymers, glass-formers, H-bond polar, ionic or van der Waals liquids. This result implies that molecules in the liquid state may not be dynamically free but weaklyelastically correlated. Using the birefringent properties of the pretransitional fluctuations coexisting in the isotropic phase of liquid crystals, we show that it is possible to visualize these “hidden” shear-elastic correlations. We detect a synchronized birefringent optical response in the isotropic phase that is observable at frequencies as low as 0.01 Hz and at temperatures far away from anyphase transition. The low-frequency birefringence exhibits a strain dependence similar to the low frequency elasticity: An optical signal that is in-phase with the strain at low strain amplitudes and in-phase with the strain-rate at larger strain amplitudes. The birefringent response is strong, defect-free, reversible and points out a collective response. This long-range ordering rules out the condition of an isotropic liquid and its synchronized response supports the existenceof long-range elastic (solid-like) correlations. In the light of this, the strain dependence of the harmonic birefringent signal and the shear elasticity may correspond to an entropy-driven transition

APA, Harvard, Vancouver, ISO, and other styles

13

Chan, Weng Yew, and chanwengyew@gmail com. "Simulation of arterial stenosis incorporating fluid-structural interaction and non-Newtonian blood flow." RMIT University. Aerospace, Mechanical and Manufacturing Engineering, 2006. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20070108.164458.

Full text

Abstract:

The aim of this study is to investigate the fluid-structural response to pulsatile Newtonian and non-Newtonian blood flow through an axisymmetric stenosed vessel using FLOTRAN and ANSYS. This is to provide a basic understanding of atherosclerosis. The flow was set to be laminar and follows a sinusoidal waveform. The solid model was set to have isotropic elastic properties. The Fluid-Structural Interaction (FSI) coupling was two-way and iterative. Rigid and Newtonian cases were investigated to provide an understanding on the effects of incorporating FSI into the model. The wall expansion was found to decrease the axial velocity and increase the recirculation effects of the flow. To validate the models and methods used, the results were compared with the study by Lee and Xu [2002] and Ohja et al [1989]. Close comparisons were achieved, suggesting the models used were valid. Two non-Newtonian models were investigated with FSI: Carreau and Power Law models. The Carreau model fluid behaviour was very close to the Newtonian model. The Power Law model produced significant difference in viscosity, velocity and wall shear stress distributions. Pressure distribution for all models was similar. In order to quantify the changes, Importance Factor (IG) was introduced to determine the overall non-Newtonian effects at two regions: the entire flow model and about the vessel wall. The Carreau model showed reasonable values of IG whereas the Power Law model showed excessive values. Transient and geometrical effects were found to affect the Importance Factor. The stress distributions for all models were found to be similar. Highest stress occurred at the shoulders of the stenosis where a stress concentration occurred due to sharp corners of the geometry and large bending moments. The highest stresses were in the axial direction. Notable circumferential stress was found at the ends of the vessel. Carreau model produced slightly higher stresses than the other models. Wall stresses were found to be primarily influenced by internal pressure, rather than wall shear stresses.

APA, Harvard, Vancouver, ISO, and other styles

14

Wu, Ke. "Computational modelling of fluid-solid interaction problems by coupling smoothed particles hydrodynamics and the discrete element method." Thesis, University of Leeds, 2017. http://etheses.whiterose.ac.uk/19544/.

Full text

Abstract:

Discrete Element Method (DEM) and Smoothed Particles Hydrodynamics (SPH) are integrated to investigate the macroscopic dynamics of fluid-solid interaction (FSI) problems. This coupled model is originated from two different meshless methods without mesh generation, which can handle fluid-particle-structure interactions with structural deformation/failure. With SPH the fluid phase is represented by a set of SPH particle elements moving in accordance with the Navier-Stokes equations. The solid phase consists of single or multiple solid particle(s) phase and deformable structure(s) phase which are represented by DEM particle elements using a linear contact model and a linear parallel contact model to account for the interaction between particle elements, respectively. To couple the fluid phase and solid particle phase, a local volume fraction and a weighted average algorithm are proposed to reformulate the governing equations and the interaction forces. The structure phase is coupled with the fluid phase by incorporating the structure’s DEM particle elements in SPH algorithm. The interaction forces between the solid particles and the structure phases are computed using the linear contact model in DEM. The proposed model is capable of simulating simultaneously fluid-structure interaction, particleparticle interaction and fluid-particle interaction, with good agreement between complicated hybrid numerical methods and experimental results being achieved. Finally, two engineering problems in injection moulding and 3D printing process are carried out to demonstrate the capability of the integrated particle model for simulating fluid-solid interaction problems with the occurrence of structural failure.

APA, Harvard, Vancouver, ISO, and other styles

15

Rakotonirina, Andriarimina. "Fluid-solid interaction in a non-convex granular media : application to rotating drums and packed bed reactors." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEN047/document.

Full text

Abstract:

Cette thèse porte sur l'étude numérique des écoulements fluide-particules rencontrés dans l'industrie. Ces travaux se situent dans le cadre de la compréhension des phénomènes qui se déroulent dans des tambours tournants et réacteurs à lit fixe en présence de particules de forme non convexe. En effet, la forme des particules influence de manière importante la dynamique de ces milieux. A cet effet, nous nous sommes servis de la plateforme numérique parallèle Grans3D pour la dynamique des milieux granulaires et PeliGRIFF pour les écoulements multiphasiques. Dans la première partie de cette thèse, nous avons développé une nouvelle stratégie numérique qui permet de prendre en compte des particules de forme arbitrairement non convexe dans le solveur Grains3D. Elle consiste à décomposer une forme non convexe en plusieurs formes convexes quelconques. Nous avons nommé cette méthode « glued-convex ». Le modèle a été validé avec succès sur des résultats théoriques et expérimentaux de tambours tournants en présence de particules en forme de croix. Nous avons aussi utilisé le modèle pour simuler le chargement de réacteurs à lits fixes puis des lois de corrélation sur les taux de vide ont été déduites de nos résultats numériques. Dans ces travaux, nous avons aussi testé les performances parallèles de nos outils sur des simulations numériques à grande échelle de divers systèmes de particules convexes. La deuxième partie de cette thèse a été consacrée à l'extension du solveur PeliGRIFF à pouvoir prendre en compte la présence de particules multilobées (non convexes) dans des écoulements monophasiques. Une approche du type Simulation Numérique Directe, basée sur les Multiplicateurs de Lagrange Distribués / Domaine Fictif (DLM/FD), a alors été adoptée pour résoudre l'écoulement autour des particules. Une série d'études de convergence spatiale a été faite basée sur diverses configurations et divers régimes. Enfin, ces outils ont été utilisés pour simuler des écoulements au travers de lits fixes de particules de forme multi-lobée dans le but d'étudier l'influence de la forme des particules sur l'hydrodynamique dans ces lits. Les résultats ont montré une consistance avec les résultats expérimentaux disponibles dans la littérature
Non convex granular media are involved in many industrial processes as, e.g., particle calcination/drying in rotating drums or solid catalyst particles in chemical reactors. In the case of optimizing the shape of catalysts, the experimental discrimination of new shapes based on packing density and pressure drop proved to be difficult due to the limited control of size distribution and loading procedure. There is therefore a strong interest in developing numerical tools to predict the dynamics of granular media made of particles of arbitrary shape and to simulate the flow of a fluid (either liquid or gas) around these particles. Non-convex particles are even more challenging than convex particles due to the potential multiplicity of contact points between two solid bodies. In this work, we implement new numerical strategies in our home made high-fidelity parallel numerical tools: Grains3D for granular dynamics of solid particles and PeliGRIFF for reactive fluid/solid flows. The first part of this work consists in extending the modelling capabilities of Grains3D from convex to non-convex particles based on the decomposition of a non-convex shape into a set of convex particles. We validate our numerical model with existing analytical solutions and experimental data on a rotating drum filled with 2D cross particle shapes. We also use Grains3D to study the loading of semi-periodic small size reactors with trilobic and quadralobic particles. The second part of this work consists in extending the modelling capabilities of PeliGRIFF to handle poly-lobed (and hence non-convex) particles. Our Particle Resolved Simulation (PRS) method is based on a Distributed Lagrange Multiplier / Fictitious Domain (DLM/FD) formulation combined with a Finite Volume / Staggered Grid (FV/SG) discretization scheme. Due to the lack of analytical solutions and experimental data, we assess the accuracy of our PRS method by examining the space convergence of the computed solution in assorted flow configurations such as the flow through a periodic array of poly-lobed particles and the flow in a small size packed bed reactor. Our simulation results are overall consistent with previous experimental work

APA, Harvard, Vancouver, ISO, and other styles

16

Cao, Shunxiang. "Numerical Methods for Fluid-Solid Coupled Simulations: Robin Interface Conditions and Shock-Dominated Applications." Diss., Virginia Tech, 2019. http://hdl.handle.net/10919/93514.

Full text

Abstract:

This dissertation investigates the development of numerical algorithms for coupling computational fluid dynamics (CFD) and computational solid dynamics (CSD) solvers, and the use of these solvers for simulating fluid-solid interaction (FSI) problems involving large deformation, shock waves, and multiphase flow. The dissertation consists of two parts. The first part investigates the use of Robin interface conditions to resolve the well-known numerical added-mass instability, which affects partitioned coupling procedures for solving problems with incompressible flow and strong added-mass effect. First, a one-parameter Robin interface condition is developed by linearly combining the conventional Dirichlet and Neumann interface conditions. Next, a numerical algorithm is developed to implement the Robin interface condition in an embedded boundary method for coupling a parallel, projection-based incompressible viscous flow solver with a nonlinear finite element solid solver. Both an analytical study and a numerical study reveal that the new algorithm can clearly outperform conventional Dirichlet-Neumann procedures in terms of both stability and accuracy, when the parameter value is carefully selected. Moreover, the studies also indicate that the optimal parameter value depends on the materials and geometry of the problem. Therefore, to efficiently solve FSI problems involving non-uniform structures, a generalized Robin interface condition is presented, in which the constant parameter is replaced by a spatially varying function that depends on the local material and geometric properties of the structure. Numerical experiments using two benchmark problems show that the spatially varying Robin interface condition can clearly improve numerical accuracy compared to the constant- parameter version with the same computational cost. The second part of this dissertation focuses on simulating complex FSI problems featuring shock waves, multiphase flow (e.g., bubbles), and shock-induced material damage and fracture. A recently developed three-dimensional computational framework is employed, which couples a multiphase, compressible CFD solver and a nonlinear finite element CSD solver using an embedded boundary method and a partitioned procedure. In particular, the CFD solver applies a level-set method to capture the evolution of the bubble surface, and the CSD solver utilizes a continuum damage mechanics model and an element erosion method to simulate the dynamic fracture of the material. Two computational studies are presented. The first one investigates the dynamic response and failure of a brittle material exposed to a prescribed shock wave. The predictive capability of the computational framework is first demonstrated by simulating a series of laboratory experiments in the context of shock wave lithotripsy. Then, a parametric study is conducted to elucidate the significant effects of the shock wave's profile on material damage. In the second study, the computational framework is applied to simulate shock-induced bubble collapse near various solid and soft materials. The reciprocal effect of the material's properties (e.g., acoustic impedance, Young's modulus) on bubble dynamics is discussed in detail.
Doctor of Philosophy
Numerical simulations that couple computational fluid dynamics (CFD) solvers and computational solid dynamics (CSD) solvers have been widely used in the solution of nonlinear fluid-solid interaction (FSI) problems underlying many engineering applications. This is primarily because they are based on partitioned solutions of fluid and solid subsystems, which facilitates the use of existing numerical methods and computational codes developed for each subsystem. The first part of this dissertation focuses on developing advanced numerical algorithms for coupling the two subsystems. The aim is to resolve a major numerical instability issue that occurs when solving problems involving incompressible, heavy fluids and thin, lightweight structures. Specifically, this work first presents a new coupling algorithm based on a one-parameter Robin interface condition. An embedded boundary method is developed to enforce the Robin interface condition, which can be advantageous in solving problems involving complex geometry and large deformation. The new coupling algorithm has been shown to significantly improve numerical stability when the constant parameter is carefully selected. Next, the constant parameter is generalized into a spatially varying function whose local value is determined by the local material and geometric properties of the structure. Numerical studies show that when solving FSI problems involving non-uniform structures, using this spatially varying Robin interface condition can outperform the constant-parameter version in both stability and accuracy under the same computational cost. In the second part of this dissertation, a recently developed three-dimensional multiphase CFD - CSD coupled solver is extended to simulate complex FSI problems featuring shock wave, bubbles, and material damage and fracture. The aim is to understand the material’s response to loading induced by a shock wave and the collapse of nearby bubbles, which is important for advancing the beneficial use of shock wave and bubble collapse for material modification. Two computational studies are presented. The first one investigates the dynamic response and failure of a brittle material exposed to a prescribed shock wave. The causal relationship between shock loading and material failure, and the effects of the shock wave’s profile on material damage are discussed. The second study investigates the shock-induced bubble collapse near various solid and soft materials. The two-way interaction between bubble dynamics and materials response, and the reciprocal effects of the material’s properties are discussed in detail.

APA, Harvard, Vancouver, ISO, and other styles

17

Wang, Chao. "Static, dynamic and levitation characteristics of squeeze film air journal bearing : designing, modelling, simulation and fluid solid interaction." Thesis, Brunel University, 2011. http://bura.brunel.ac.uk/handle/2438/5832.

Full text

Abstract:

Bearings today need to be able to run at very high speed, providing high positional accuracy for the structure that it supports, and requiring very little or no maintenance. For this to happen, bearings must have tight tolerances and very low or zero friction during operation. This pushes many traditional contact-type bearings to their limits as they often fail due to friction, generating heat and causing wear. By comparison, existing non-contact bearings fare better because of their very low or zero friction. But some have their own problem too. For example, the fact that aerostatic bearings require an air supply means having to use a separate air compressor and connecting hoses. This makes the installation bulky. Aerodynamic and hydrodynamic bearings cannot support loads at zero speed. Both hydrodynamic and hydrostatic bearings may cause contamination to the work-pieces and the work environment because of the use of lubricating fluid. A potential solution to the above-mentioned problems is the new squeeze film air bearing. It works on the rapid squeeze action of an air film to produce separation between two metal surfaces. This has the benefit of being compact with a very simple configuration because it does not require an external pressurized air supply, can support loads at zero speed and is free of contamination. For this research, two squeeze film air journal bearings, made from material of Al 2024 - T3 and Cu - C101 with the same geometry, were designed. The bearing is in the shape of a round tube with three fins on the outer surface and the journal, a round rod. When excited at a certain normal mode, the bearing shell flexes with a desirable modal shape for the squeeze film action. The various modes of vibration of Al bearing were obtained from a finite-element model implemented in ANSYS. Two Modes, the 13th and 23rd, at the respective frequencies of 16.320 kHz and 25.322 kHz, were identified for further investigation by experiments with respect to the squeeze film thickness and its load-carrying capacity. For Cu bearing, the two Modes are also 13th and 23rd at the respective frequencies of 12.184 kHz and 18.459 kHz. In order to produce dynamic deformation of the bearings at their modes, a single layer piezoelectric actuator was used as a driver. The maximum stroke length and the maximum blocking force of the single layer piezoelectric actuator were determined using manual calculation and ANSYS simulation. In the coupled-field analysis, the single layer piezoelectric actuator was mounted on the outside surface of the bearing shell and loaded with an AC and a DC voltage in order to produce the static and dynamic deformation. For the static analysis, the maximum deformation of Al bearing shell is 0.124 μm when the actuators are driven at the DC of 75 V. For the dynamic analysis, the actuators are driven at three levels of AC, namely 55, 65 and 75V with a constant DC offset of 75V and the driving frequency coincided with the modal frequency of the bearing. The maximum dynamic deformation of Al bearing shell is 3.22μm at Mode 13 and 2.08μm at Mode 23 when the actuators were driven at the AC of 75 V and the DC of 75 V. Similarly, the FEA simulation was used for analyzing Cu bearing. Furthermore, the dynamic deformation of both Al and Cu bearing at Mode 13 and 23 are validated by experiments. This research developed two theoretical models that explain the existence of a net pressure in a squeeze film for the levitation. The first model uses the ideal gas law as first approximation whilst the second uses the CFX simulation to provide a more exact explanation. In terms of the load-carrying capacity, Mode 13 was identified to be better than Mode 23 for both bearings. However, at Mode 13, Al bearing has a higher load-carrying capacity than Cu bearing. This is due to Al bearing having a higher modal frequency and amplitude. Finally, the coupled-field analysis for fluid solid interaction (FSI) was studied at both Mode 13 and 23 for Al bearing. The findings are that: a) the fluid force in the squeeze film can affect the dynamic deformation of the bearing shell, especially at high oscillation frequency, more at Mode 13 than at Mode 23 due to the relatively high pressure end-leakage in the latter; b) the dynamic deformation of the bearing shell increases with the gap clearance in a logarithmic manner at Mode 13; and c) the micron levels of gap clearance provide a damping effect on the dynamic deformation of the bearing shell at Mode 13 and at Mode 23, though much less dominant.

APA, Harvard, Vancouver, ISO, and other styles

18

Hosseini, Kordkheili Seyed. "A new continuum based non-linear finite element formulation for modeling of dynamic response of deep water riser behavior." Thesis, Brunel University, 2009. http://bura.brunel.ac.uk/handle/2438/4068.

Full text

Abstract:

The principal objective of this investigation is to develop a nonlinear continuum based finite element formulation to examine dynamic response of flexible riser structures with large displacement and large rotation. Updated Lagrangian incremental approach together with the 2nd Piola-Kirchhoff stress tensor and the Green-Lagrange strain tensor is employed to derive the nonlinear finite element formulation. The 2nd Piola-Kirchhoff stress and the Green-Lagrange strain tensors are energy conjugates. These two Lagrangian tensors are not affected by rigid body rotations. Thus, they are used to describe the equilibrium equation of the body independent of rigid rotations. While the current configuration in Updated Lagrangian incremental approach is unknown, the resulting equation becomes strongly nonlinear and has to be modified to a linearized form. The main contribution of this work is to obtain a modified linearization method during development of incremental Updated Lagrangian formulation for large displacement and large rotation analysis of riser structures. For this purpose, the Green-Lagrange strain and the 2nd Piola-Kirchhoff stress tensors are decomposed into two second-order six termed functions of through-thethickness parameters. This decomposition makes it possible to explicitly account for the nonlinearities in the direction along the riser thickness, as well. It is noted that using this linearization scheme avoids inaccuracies normally associated with other linearization schemes. The effects of buoyancy force, riser-seabed interaction as well as steady-state current loading are considered in the finite element solution for riser structure response. An efficient riser problem fluid-solid interaction Algorithm is also developed to maintain the quality of the mesh in the vicinity of the riser surface during riser and fluid mesh movements. To avoid distortions in the fluid mesh two different approaches are proposed to modify fluid mesh movement governing elasticity equation matrices values; 1) taking the element volume into account 2) taking both element volume and distance between riser centre and element centre into account. The formulation has been implemented in a nonlinear finite element code and the results are compared with those obtained from other schemes reported in the literature.

APA, Harvard, Vancouver, ISO, and other styles

19

Rolle, Trenicka. "Lung Alveolar and Tissue Analysis Under Mechanical Ventilation." VCU Scholars Compass, 2014. http://scholarscompass.vcu.edu/etd/3398.

Full text

Abstract:

Mechanical ventilation has been a major therapy used by physicians in support of surgery as well as for treating patients with reduced lung function. Despite its many positive outcomes and ability to maintain life, in many cases, it has also led to increased injury of the lungs, further exacerbating the diseased state. Numerous studies have investigated the effects of long term ventilation with respect to lungs, however, the connection between the global deformation of the whole organ and the strains reaching the alveolar walls remains unclear. The walls of lung alveoli also called the alveolar septum are characterized as a multilayer heterogeneous biological tissue. In cases where damage to this parenchymal structure insist, alveolar overdistension occurs. Therefore, damage is most profound at the alveolar level and the deformation as a result of such mechanical forces must be investigated thoroughly. This study investigates a three-dimensional lung alveolar model from generations 22 (alveolar ducts) through 24 (alveoli sacs) in order to estimate the strain/stress levels under mechanical ventilation conditions. Additionally, a multilayer alveolar tissue model was generated to investigate localized damage at the alveolar wall. Using ANSYS, a commercial finite element software package, a fluid-structure interaction analysis (FSI) was performed on both models. Various cases were simulated that included a normal healthy lung, normal lung with structural changes to model disease and normal lung with mechanical property changes to model aging. In the alveolar tissue analysis, strains obtained from the aged lung alveolar analysis were applied as a boundary condition and used to obtain the mechanical forces exerted as a result. This work seeks to give both a qualitative and quantitative description of the stress/strain fields exerted at the alveolar region of the lungs. Regions of stress/strain concentration will be identified in order to gain perspective on where excess damage may occur. Such damage can lead to overdistension and possible collapse of a single alveolus. Furthermore, such regions of intensified stress/strain are translated to the cellular level and offset a signaling cascade. Hence, this work will provide distributions of mechanical forces across alveolar and tissue models as well as significant quantifications of damaging stresses and strains.

APA, Harvard, Vancouver, ISO, and other styles

20

Balakrishnan, Mahalingam III. "The Role of Turbulence on the Entrainment of a Single Sphere and the Effects of Roughness on Fluid-Solid Interaction." Diss., Virginia Tech, 1997. http://hdl.handle.net/10919/30732.

Full text

Abstract:

Incipient motion criterion in sediment transport is very important, as it defines the flow condition that initiates sediment motion, and is also frequently employed in models to predict the sediment transport at higher flow conditions as well. In turbulent flows, even a reasonably accurate definition of incipient motion condition becomes very difficult due to the random nature of the turbulent process, which is responsible for sediment motion under incipient conditions. This work investigates two aspects, both of which apply to incipient sediment transport conditions. The first one deals with the role of turbulence in initiating sediment motion. The second part deals with the nature of sediment-fluid interaction for more general and complex flows where the number of sediment particles that form the rough surface is varied. The first part of this work that investigates the role of turbulence in initiating sediment motion, uses a video camera to simultaneously monitor and record the sediment (glass ball) motion and corresponding fluid velocity events measured by a three-component laser Doppler Velocimeter (LDV). The results of the single ball experiment revealed that the number of LDV flow measurements increase dramatically (more than four folds) just prior to the ball motion. The fluid mean velocity and its root-mean-square (rms) values also are significantly higher than the values that correspond to the flow conditions that yield no ball motion. The second part of the work, investigation of the fluid-sediment interaction, includes five tests with varying number of sediment particles. In order to understand the nature and extent of fluid-solid interaction, velocity profile measurements using the 3-D laser system were carried out at three locations for each of these five cases. Plots of mean velocities, rms quantities located the universal layer at about 1.5 ball diameters above the porous bed. However, at higher sediment particle concentrations, this distance reduced and the beginning of the universal layer approached the top of the porous bed.
Ph. D.

APA, Harvard, Vancouver, ISO, and other styles

21

Ndanou, Serge. "Etude mathématique et numérique des modèles hyperélastiques et visco-plastiques : applications aux impacts hypervéloces." Thesis, Aix-Marseille, 2014. http://www.theses.fr/2014AIXM4347/document.

Full text

Abstract:

Un modèle mathématique d'interfaces diffuses pour l'interaction de N solides élasto-plastiques a été construit. C'est une extension du modèle développé par Favrie & Gavrilyuk (2012) pour l'interaction d'un fluide et d'un solide. En dépit du grand nombre d'équations présentes dans ce modèle, deux propriétés remarquables ont été démontrées : ce modèle est hyperbolique (quelles que soient les déformations admissibles) et il vérifie le second principe de la thermodynamique. En dépit du grand nombre d'équations présentes dans ce modèle, deux propriétés remarquables ont été démontrées: ce modèle est hyperbolique (quelles que soient les déformations admissibles) et il vérifie le second principe de la thermodynamique. L'énergie interne de chaque solide est prise sous forme séparable: c'est la somme d'une énergie hydrodynamique qui ne dépend que de la densité et de l'entropie, et d'une énergie de cisaillement. L'équation d'état de chaque solide est telle que si nous prenons le module de cisaillement du solide égale à zéro, on retrouve les équations de la mécanique des fluides. Ce modèle permet, en particulier, de:- prédire les déformations de solides élasto-plastiques en petites déformations et en très grandes déformations.- prédire l'interaction d'un nombre arbitraire de solides élasto-plastiqueset de fluides. L'aptitude de ce modèle à résoudre des problèmes complexes a été démontrée. Sans être exhaustif, on peut citer:-le phénomène d'écaillage dans les solides.- La fracturation et la fragmentation dynamique dans les solides
A mathematical model of diffuse interface for the interaction of N elasto-plastic solidS was built. It is an extension of the model developed by Favrie & Gavrilyuk (2012) for a fluid-solid interaction. Despite the large number of equations present in this model, two remarkable properties have been demonstrated: it is hyperbolic for any admissible deformations and satisfies the second principle of thermodynamics. In this model, the internal energy of each solid is taken in separable form: it is the sum of a hydrodynamic energy (which depends only on the density and entropy) and shear energy. The equation of state of each solid is such that if we take the shear modulus of the solid vanishes, we find the equations of fluid mechanics. This model allows, in particular:- predict the deformation of elastic-plastic solids in small and very large deformations.- predict the interaction of an arbitrary number of elasto-plastic solids and fluids.The ability of this model to solve complex problems has been demonstrated. Without being exhaustive, one can mention:- the spall phenomenon in solids.- fracturing and fragmentation in solids

APA, Harvard, Vancouver, ISO, and other styles

22

Selino, Anthony Frank. "Coherent Turbulence: Synthesizing tree motion in the wind using CFD and noise." BYU ScholarsArchive, 2011. https://scholarsarchive.byu.edu/etd/3015.

Full text

Abstract:

Animating trees in wind has long been a problem in computer graphics. Progress on this problem is important for both visual effects and biomechanics and may inform future work on two-way coupling between turbulent flows and deformable objects. Synthetic turbulence added to a coarse fluid simulation has been used to produce convincing animations of turbulent flows, but only considers one-way coupling between fluid and solid. We produce accurate animations of tree motion by creating a two-way coupling between synthetic turbulence and semipermeable proxy geometry. The resulting animations exhibit global wind sheltering effects and branch tips have motion paths which match paths collected from branch tips using motion capture.

APA, Harvard, Vancouver, ISO, and other styles

23

Ager, Christoph Franz [Verfasser], Wolfgang A. [Akademischer Betreuer] Wall, Wolfgang A. [Gutachter] Wall, and Marek [Gutachter] Behr. "Computational Methods for Fluid-Structure Interaction including Porous Media and Solid Contact / Christoph Franz Ager ; Gutachter: Wolfgang A. Wall, Marek Behr ; Betreuer: Wolfgang A. Wall." München : Universitätsbibliothek der TU München, 2021. http://d-nb.info/1230985131/34.

Full text

APA, Harvard, Vancouver, ISO, and other styles

24

Bergström, Stina. "Added Properties in Kaplan Turbine - a preliminary investigation." Thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-60925.

Full text

Abstract:

A preliminary investigation of the added properties called added mass, added damping and added stiffness have been performed for a Kaplan turbine. The magnitude of dimensionless numbers have been used in order to classify the interaction of the fluid and the solid. The classification is done to bring clarity in which of the added properties are of importance for the system. The diameter of the runner and the hub have been calculated using the power output and the head for a Kaplan turbine. These dimensions have been used to determine the magnitude of the dimensionless numbers along with the velocity of the fluid. It turned out that all added properties affect the turbine, however, the magnitude of them are quite different. The magnitude of the added mass and the added damping are greater than the added stiffness, which often is neglected. The added mass can be determined if the natural frequencies of the structure in air and in water are known. The difference in natural frequencies can be used to determine the added mass factor and thereby the added mass of the system. The added damping can be determined by the change in damping ratio for different surrounding fluids. This was done using the simulation software ANSYS Workbench v.17.1, where two different types of simulation were used, ”acoustic coupled simulation” and ”two way coupled simulation”. The complexity of the geometry of the Kaplan turbine was simplified to a disc and a shaft. The result for the added mass was validated using results from an experiment [1]. The added damping could be determined, but not validated. The different types of simulation have been compared and it turned out that the added mass could be determined using ”acoustic coupled simulation” and ”two way coupled simulation”, but the added damping could only be determined using the ”two way coupled simulation”.
En preliminär undersökning av de adderade egenskaperna kallade, adderad massa, adderad dämpning och adderad styvhet har utförts för en Kaplan turbin. Magnituden av dimensionslösa tal har använts för att klassificera interaktionen av fluiden och soliden. Klassificeringen görs för att bringa klarhet i vilka av de adderade egenskaperna är av betydelse för systemet. Diametrarna för löphjulet och navet har beräknats utifrån effekt och fallhöjd för en Kaplan turbin. Dessa längder har använts för att bestämma magnituden av de dimensionslösa talen tillsammans med fluidens hastighet. Det visade sig att alla adderade egenskaper påverkar turbinen, men omfattningen av dem är helt annorlunda. Magnituden av den adderade massan och den adderade dämpningen är större än den adderade styvheten, som ofta försummas. Den adderade massan kan bestämmas om de naturliga frekvenserna av strukturen i luft och vatten är kända. Skillnaden i egenfrekvenser kan användas för att bestämma faktorn av den adderade massan och därigenom den adderade massan. Den adderade dämpningen kan bestämmas genom ändringen i dämpningsförhållande för olika omgivande fluider. Detta gjordes med hjälp av simuleringsprogrammet ANSYS Workbench v.17.1, där två olika typer av simulering användes, ”acoustic coupled simulation” och ”two way coupled simulation”. Komplexiteten i geometrin för en Kaplan turbin förenklades till en skiva och en axel. Resultatet för den adderade massan validerades med resultat från ett experiment [1]. Den adderade dämpningen kunde bestämmas, men inte valideras. De olika typerna av simulering har jämförts och det visade sig att den adderade massan kan bestämmas med hjälp av både ”acoustic coupled simulation” och ”two way coupled simulation”, men den adderade dämpningen kunde endast bestämmas med hjälp av ”two way coupled simulation”.

APA, Harvard, Vancouver, ISO, and other styles

25

Sirivolu, Dushyanth. "Marine Composite Panels under Blast Loading." University of Akron / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=akron1467993101.

Full text

APA, Harvard, Vancouver, ISO, and other styles

26

Junior, Rubens Augusto Amaro. "Simulação computacional do comportamento elástico de materiais pelo método de partículas Moving Particle Semi-implicit (MPS)." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/3/3146/tde-10072014-170459/.

Full text

Abstract:

Neste trabalho um método de partículas para simular a dinâmica de sólidos elásticos e interação fluido estrutura e implementado. O método e baseado no Moving Particle Semi-implicit (MPS), originalmente desenvolvido para escoamentos incompressíveis com superfície livre. A estratégia principal do MPS e substituir os operadores diferenciais das equações governantes por operadores diferenciais discretos em uma distribuição de nos irregulares, derivados de um modelo de interação entre partículas. Inicialmente são apresentados os detalhes da formulação do método e modelos constitutivos utilizados. Uma condição simplificada de fragmentação e proposta, assim como um algoritmo de detecção de contato, permitindo a fragmentação entre vários sólidos. No caso da interação fluido-estrutura, as partículas de superfície do solido são tratadas como partículas de fluido e as pressões destas partículas são calculadas pela resolução da equação de Poisson para a pressão, tal como as partículas de fluido. Desta forma, o acoplamento entre solido e fluido e realizado utilizando o deslocamento e velocidade do solido elástico, como condições de contorno do fluido, e a pressão na interface, obtida pela resolução do movimento do fluido, e aplicada ao movimento do solido elástico. São apresentados e detalhados os algoritmos de solido elástico, fragmentação, colisão e acoplamento fluido-estrutura. Validações qualitativas e quantitativas do método são realizadas para casos estáticos e dinâmicos sujeitos a diferentes condições de contorno, comparando os resultados numéricos obtidos pelo MPS, outros métodos numéricos, soluções analíticas e medições experimentais presentes na literatura.
In this work a particle method to simulate the dynamics of elastic solids and fluid-structure interaction is implemented. It is based on the Moving Particle Semi-implicit Method (MPS), which was originally developed for incompressible flows with free surface. The main strategy of the MPS is to replace the differential operators of the governing equations by discrete differential operators on irregular nodes, which are derived from a model of interaction between particles. Initially details of the method and constitutive equations are shown. A simplified condition of fragmentation and collision between solids are proposed to allow the investigation of fragmentation amount multiple solids. In case of fluid-structure interaction, the solid\'s surface particles are treated as a fluid particle and the pressures of the surface particles are computed by solving Poisson equation for the pressure, just as the fluid particles. Therefore, the coupling between solid and fluid is done by using the displacement and velocity of elastic solid as the boundary conditions of the fluid, and the pressure at the interface, which is obtained when solving the fluid motion, is used to calculate the motion of the elastic solid. The algorithms for elastic solid, fragmentation, collision and fluid-structure interaction are presented and detailed. The qualitative and quantitative validations of the method are carried out herein considering static and dynamic cases subjected to deferent boundary conditions by comparing the numerical results from MPS with other numerical, analytical and experimental results available in the literature.

APA, Harvard, Vancouver, ISO, and other styles

27

Jentsch, L., and D. Natroshvili. "Interaction between Thermoelastic and Scalar Oscillation Fields (general anisotropic case)." Universitätsbibliothek Chemnitz, 1998. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-199801162.

Full text

Abstract:

Three-dimensional mathematical problems of the interaction between thermoelastic and scalar oscillation fields are considered in a general anisotropic case. An elastic structure is assumed to be a bounded homogeneous anisortopic body occupying domain $\Omega^+\sub\R^3$ , where the thermoelastic field is defined, while in the physically anisotropic unbounded exterior domain $\Omega^-=\R^3\\ \overline{\Omega^+}$ there is defined the scalar field. These two fields satisfy the differential equations of steady state oscillations in the corresponding domains along with the transmission conditions of special type on the interface $\delta\Omega^{+-}$. Uniqueness and existence theorems, for the non-resonance case, are proved by the reduction of the original interface problems to equivalent systems of boundary pseudodifferential equations ($\Psi DEs$) . The invertibility of the corresponding matrix pseudodifferential operators ($\Psi DO$) in appropriate functional spaces is shown on the basis of generalized Sommerfeld-Kupradze type thermoradiation conditions for anisotropic bodies. In the resonance case, the co-kernels of the $\Psi DOs$ are analysed and the efficent conditions of solvability of the transmission problems are established.

APA, Harvard, Vancouver, ISO, and other styles

28

Sabbagh, Lamis Marlyn Kenedy. "Study of rigid solids movement in a viscous fluid." Thesis, Montpellier, 2018. http://www.theses.fr/2018MONTS103/document.

Full text

Abstract:

Cette thèse est consacrée à l’analyse mathématique du problème du mouvement d’un nombre fini de corps rigides homogènes au sein d’un fluide visqueux incompressible homogène. Les fluides visqueux sont classés en deux catégories: les fluides newtoniens et les fluides non newtoniens. En premier lieu, nous considérons le système formé par les équations de Navier Stokes incompressible couplées aux lois de Newton pour décrire le mouvement de plusieurs disques rigides dans un fluide newtonien visqueux homogène dans l’ensemble de l’espace R^2. Nous montrons que ce problème est bien posé jusqu’à l’apparition de la première collision. Ensuite, nous éliminons tous les types de contacts pouvant survenir si le domaine fluide reste connexe à tout moment. Avec cette hypothèse, le système considéré est globalement bien posé. Dans la deuxième partie de cette thèse, nous montrons la non-unicité des solutions faibles au problème d’interaction fluide-solide 3D, dans le cas d’un fluide newtonien, après collision. Nous montrons qu’il existe des conditions initiales telles que nous pouvons étendre les solutions faibles après le temps pour lequel le contact a eu lieu de deux manières différentes. Enfin, dans la dernière partie, nous étudions le mouvement bidimensionnel d’un nombre fini de disques immergés dans une cavité remplie d’un fluide viscoélastique tel que des solutions polymériques. Les équations de Navier Stokes incompressible sont utilisées pour modéliser le solvant, dans lesquelles un tenseur de contrainte élastique supplémentaire apparaît comme un terme source. Dans cette partie, nous supposons que le tenseur de contrainte supplémentaire satisfait la loi différentielle d’Oldroyd ou sa version régularisée. Dans les deux cas, nous prouvons l’existence et l’unicité des solutions fortes locales en temps du problème considéré
This thesis is devoted to the mathematical analysis of the problem of motion of afinite number of homogeneous rigid bodies within a homogeneous incompressible viscous fluid. Viscous fluids are classified into two categories: Newtonian fluids, and non-Newtonian fluids. First, we consider the system formed by the incompressible Navier-Stokes equations coupled with Newton’s laws to describe the movement of several rigid disks within a homogeneous viscous Newtonian fluid in the whole space R^2. We show the well-posedness of this system up to the occurrence of the first collision. Then we eliminate all type of contacts that may occur if the fluid domain remains connected at any time. With this assumption, the considered system is well-posed globally in time. In the second part of this thesis, we prove the non-uniqueness of weak solutions to the fluid-rigid body interaction problem in 3D in Newtonian fluid after collision. We show that there exist some initial conditions such that we can extend weak solutions after the time for which contact has taken place by two different ways. Finally, in the last part, we study the two-dimensional motion of a finite number of disks immersed in a cavity filled with a viscoelastic fluid such as polymeric solutions. The incompressible Navier–Stokes equations are used to model the flow of the solvent, in which the elastic extra stress tensor appears as a source term. In this part, we suppose that the extra stress tensor satisfies either the Oldroyd or the regularized Oldroyd constitutive differential law. In both cases, we prove the existence and uniqueness of local-in-time strongsolutions of the considered moving-boundary problem

APA, Harvard, Vancouver, ISO, and other styles

29

Cerqueira, Stéphane. "Étude du couplage aéro-mécanique au sein des moteurs à propergol solide." Thesis, Paris, ENMP, 2012. http://www.theses.fr/2012ENMP0011/document.

Full text

Abstract:

Les Moteurs à Propergol Solide sont le siège d'instabilités de combustion qui se manifestent par des fluctuations de la pression interne et, en conséquence, de la poussée induite. Les phénomènes oscillatoires observés résultent d'un couplage entre l'acoustique de la chambre de combustion et une ou plusieurs instabilités hydrodynamiques de l'écoulement interne.Dans cette thèse, on s'intéresse à l'étude de l'écoulement induit par injection pariétale en géométrie axisymétrique. Plus particulièrement, on se concentre sur l'interaction qui peut avoir lieu entre cet écoulement et une structure : les Protections Thermiques de Face.Une étude expérimentale reposant sur le montage gaz froid VALDO de l'ONERA, modélisation représentative des MPS P230, a permis d'examiner l'influence d'obstacles, rigides et en élastomère, sur les instationnarités de l'écoulement. Le caractère instable de l'écoulement induit par injection pariétale est alors confirmé et le rôle primordial joué par les PTF sur les fréquences émergeant au sein de l'écoulement a été identifié.L'analyse de stabilité linéaire de l'écoulement, conduite en approche globale, permet l'étude de sa dynamique en tant qu'amplificateur de bruit. Les m¶mécanismes mis en jeu dans l'instabilité de l'écoulement induit par injection pariétale ainsi que son interaction complexe avec la couche de cisaillement issue de l'obstacle sont analysés. La réponse de l'écoulement à un forçage harmonique est alors examinée à la lumière des résultats expérimentaux.Cette étude a été complétée par une approche numérique de l'Interaction Fluide-Structure sur une configuration jugée critique. Une étape préliminaire à la simulation multi-physique est l'élaboration d'un modèle réaliste du comportement des PTF en élastomère. L'identification et la prise en considération des mécanismes propres aux élastomères dans la loi de comportement est ainsi détaillée. Les résultats issus des simulations sont confrontés aux résultats expérimentaux et rendent possible la validation d'un scénario de couplage dédié à l'Interaction Fluide-Structure au sein des MPS
Fluid Structure Interaction of an inhibitor with the internal flow induced by wall injection was studied in an axisymmetric cold flow apparatus. Experiments were carried out over a wide range of injection velocities in order to underline how the obstacle not only modifies the mean flowfield but also its entire dynamic behaviour.The resulting instability (from the interaction of the unstable shear layer with the Taylor-Culick flow) exhibits a significant shift with respect to the Taylor-Culick instability and therefore emphasizes the strong impact of the inhibitor on hydrodynamics.The mecanisms responsible of such behaviour are studied in this thesis with the help of global linear stability analysis and multi-physics numerical computations

APA, Harvard, Vancouver, ISO, and other styles

30

Gineau, Audrey Nathalie. "Modélisation multi-échelle de l'interaction fluide-structure dans les systèmes tubulaires." Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066651/document.

Full text

Abstract:

Cette thèse a pour objectif de modéliser le couplage fluide-structure pouvant survenir dans les faisceaux tubulaires des réacteurs nucléaires. Leurs simulations numériques directes étant hors de portée, on met en œuvre une approche multi-échelle: il s'agit de tirer profit du coût modeste d'une description macroscopique, et à la fois, de la précision des informations microscopiques. Vis-à-vis des modèles existants, le travail de développement se focalise sur la prise en compte de la convection dans le calcul des champs hydrodynamiques, mais surtout, sur la possibilité de restituer des réponses vibratoires variées au sein d'un même faisceau. L'homogénéisation aboutit à un système d'équations gouvernant les Interactions Fluide-Solide à une échelle macroscopique. Ces équations sont couplées par une source en quantité de mouvement, traduisant les charges hydrodynamiques exercées sur une structure donnée. Cette force à modéliser représente une loi de fermeture du problème homogénéisé, mettant en jeu des coefficients a priori inconnus. Une méthode d'estimation est proposée à partir des champs microscopiques obtenus par simulation directe sur un domaine réduit et représentatif du large système de référence. Les capacités prédictives du modèle homogénéisé sont évaluées en comparaison avec des données de référence, issues de calculs numériques directs microscopiques. Chaque système considéré présente une variété de réponses en déplacement que le modèle homogénéisé restitue avec un accord satisfaisant. Cette approche multi-échelle semble être un bon compromis entre le coût des réalisations numériques et la précision attendue des données vibratoires et hydrodynamiques
Vibration of tubes arrays is a matter of safety assessments of nuclear reactor cores or steam generators. Such systems count up thousands of slender-bodies immersed in viscous flow, involving multi-physics mechanisms caused by nonlinear dynamic interactions between the fluid and the solid materials. Direct numerical simulations for predicting these phenomena could derive from continuum mechanics, but require expensive computing resources. Therefore, one alternative to the costly micro-scale simulations consists in describing the interstitial fluid dynamics at the same scale as the structures one. Such approach rely on homogenization techniques intended to model mechanics of multi-phase systems. Homogenization results in coupled governing equations for the fluid and solid dynamics, whose solution provides individual tubes displacements and average fluid fields for each periodic unit cell. An hydrodynamic force term arises from the formulation within this set of homogenized equations: it depends on the micro-scale flow in the vicinity of a given tube-wall, but needs to be estimated as a function of the macro-scale fields in order to close the homogenized problem. The fluid force estimation relies on numerical micro-scale solutions of fluid-solid interactions over a tube array of small size. The multi-scale model is assessed for arrays made up of hundreds tubes, and is compared with solutions coming from the numerical micro-scale simulations. The macro-scale solution reproduces with good agreement the averaged solution of the micro-scale simulation, indicating that the homogenization method and the hydrodynamic force closure are suitable for such tube array configurations

APA, Harvard, Vancouver, ISO, and other styles

31

Djellouli, Abderrahmane. "Nage par flambage de coque sphérique." Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAY043/document.

Full text

Abstract:

Les micronageurs et parmi eux les microangeurs artificiels sont en général, limités à exister dans des écoulements dominés par des forces visqueses. Ces écoulements sont caractérisés par un bas nombre de Reynolds (Re). Cela impacte la stratégie de nage et plus particulièrement les séquences de forme possibles, qui doivent nécessairement être non-réciproques dans l'espace de déformation pour espérer induire un déplacement net non-nul. De plus, due aux forts effets de traînée, les vitesses de nage sont limités à des valeurs faibles.Dans cette thèse, on examine la possibilité d'utiliser un mécanisme de nage basé sur l'instabilité de flambage d'une sphère creuse. Cette instabilité est provoquée en soumettant la sphère à une onde de pression. La particularité de ce mécanisme est qu'il satisfait par construction la condition nécessaire de nage à bas Reynolds exposée précédemment. De plus, la rapidité de la déformation lors de l'instabilité pousse à prévoir l'apparition d'effets inertiels, et ce même à l'échelle microscopique.Une étude expérimentale a été conduite à l'échelle macroscopique dans le but de comprendre la dynamique de l'instabilité et son impact sur le fluide qui entoure la coque creuse. Ces expériences nous permettent de montrer qu'un déplacement net non-nul est produit pour tous les régimes d'écoulements.On met en évidence le rôle de paramètres géométriques, des propriétés du matériau composant la coque creuse et de la rhéologie du fluide sur l'efficacité de la nage.On montre l'existence d'un optimum de déplacement net pour des valeurs intermédiaires du nombre de Reynolds. Pour expliquer cela, on se sert de mesures de PIV résolues temporellement pour mettre en évidence la présence d'effets d'histoire non-triviaux qui augmentent le déplacement net.On dérive un simple modèle en se basant sur les observations expérimentales pour montrer que ce régime optimal de nage est atteignable pour des sphères microscopiques, ceci est possible grâce l'activation rapide de l'instabilité. Cette propriété permet aussi une excitation à haute fréquence en utilisant des ultrasons. Une étude d'échelle nous permet de prédire une vitesse de nage de 1 cm/s pour un micro-robot contrôlé à distance. Cet ordre de grandeur de vitesse est idéal pour des applications biologiques comme la distribution ciblée de médicaments
Microswimmers, and among them aspirant microrobots, are generally bound to cope with flows where viscous forces are dominant, characterized by a low Reynolds number (Re). This implies constraints on the possible sequences of body motion, which have to be nonreciprocal. Furthermore, the presence of a strong drag limits the range of resulting velocities.Here, we propose a swimming mechanism which uses the buckling instability triggered by pressure waves to propel a spherical hollow shell. The particularity of this mechanism is that it fulfills naturally the necessary condition of swimming at low Re. In addition, the swiftness of the instability might produce inertial effects even at the microscopic scale.With a macroscopic experimental model we show that a net displacement is produced at all Re regimes. We put in evidence the role of geometrical parameters, shell material properties and rheology of the surrounding fluid on the swimming efficiency.An optimal displacement is reached at intermediate Re. Using time-resolved PIV measurements, we explain that non-trivial history effects take place during the instability and enhance net displacement.Using a simple model, derived from the study of shell dynamics, we show that due to the fast activation induced by the instability, this regime is reachable by microscopic shells. The rapid dynamics would also allow high frequency excitation with standard traveling ultrasonic waves. Scale considerations predict a swimming velocity of order 1 cm/s for a remote controlled microrobot, a suitable value for biological applications such as drug delivery

APA, Harvard, Vancouver, ISO, and other styles

32

Valkov, Boris Ivanov. "A blurred interface formulation of The Reference Map Technique for Fluid-Solid Interactions and Fluid-Solid-Solid Interactions." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/92123.

Full text

Abstract:

Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2014.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 143-144).
In this work we present a blurred interface method for Fluid-Solid Interactions (FSI) and multiple solids immersed in a fluid or FSSI (Fluid-Solid-Solid Interactions) based on the reference map technique as presented by Kamrin and Rycroft. I will follow the chain of thought which lead from the initial sharp interface technique to the newer blurred interface one. We will present its capabilities of doing fully-coupled simulations of a compressible Navier-Stokes fluid and highly non-linear solid undergoing large deformations all performed on a single Eulerian grid with no Lagrangian particles whatsoever. The Reference Map Technique (RMT) provides an Eulerian simulation framework allowing to compute fully coupled fluid/soft-solid interactions. However, due to the extrapolations inherent to the Ghost Fluid Method (GFM) for fluid/fluid interactions, on which the RMT is based, numerical artifacts get created in the resulting pressure and velocity fields whenever the levelset defining the interface crosses a gridpoint from the fixed cartesian grid utilized in this method. We will therefore follow the creation and propagation of these artifacts as well as analyze how the blurred technique solves or avoids these problems.
by Boris Ivanov Valkov.
S.M.

APA, Harvard, Vancouver, ISO, and other styles

33

Svahnberg, Henrik. "Deformation behaviour and chemical signatures of anorthosites: : Examples from southern West Greenland and south-central Sweden." Doctoral thesis, Stockholms universitet, Institutionen för geologiska vetenskaper, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-42854.

Full text

Abstract:

Plagioclase is the most abundant mineral in the lower crust and it is thus important to constrain the behaviour of plagioclase during deformation. Anorthosites, which are plagioclase-rich rocks, are common in Archaean cratons but their origin and rheological importance is still debated. The aims of this thesis are to 1) describe a newly discovered Archaean anorthosite complex (Naajat Kuuat, SW Greenland), investigate its origin and a possible genetic relationship between the anorthosite and associated mafic-ultramafic rocks and 2) to study the rheology and deformation mechanisms in plagioclase-rich rocks. The main focus of this thesis is on the deformation studies. (1) Geochemical whole-rock analyses from the Naajat Kuuat complex are indicative for an origin near a subduction zone setting. A genetic link by crystal fractionation between the anorthosite and associated mafic-ultramafic units is inferred. (2) Deformation behaviour of plagioclase is assessed from analyses of three anorthosite units deformed during different conditions. Samples were analysed using the electron backscatter diffraction technique (EBSD) in combination with optical and chemical analyses. All three case studies show significant strain localisation related to grain size reduction. A wet anorthosite deformed at dry conditions (T ~675-700°C) was dynamically recrystallised. Continuous bands of recrystallised grains developed a texture yet display microstructures and grain relationships indicative for grain size sensitive creep, suggesting that the rheology followed a Newtonian flow law. In the other two studies, samples with initially dry and wet composition, respectively, have experienced deformation during fluid present conditions at T ~550-620°C. These two samples show that fluids effectively caused reactions, replacements and aided strain localisation during deformation at mid crustal conditions.
At the time of the doctoral defence the following papers were unpublished and had a status as follows: Paper 1: Manuscript; Paper 2 Manuscript; Paper 3 Manuscript.

APA, Harvard, Vancouver, ISO, and other styles

34

Heneghan, Peter. "fluid -solid-chemical interactions of the nucleus pulposus." Thesis, University of Strathclyde, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.488795.

Full text

APA, Harvard, Vancouver, ISO, and other styles

35

Gartner, Nicolas. "Identification de paramètres hydrodynamiques par simulation avec Smoothed Particle Hydrodynamics." Electronic Thesis or Diss., Toulon, 2020. http://www.theses.fr/2020TOUL0004.

Full text

Abstract:

Cette thèse porte sur les techniques de simulations des interactions dynamiques entre un véhicule sous-marin et l'eau qui l'entoure. L'objectif principal est de proposer une solution satisfaisante pour pouvoir, en amont du processus de conception, tester des algorithmes de contrôle et des formes de coques pour véhicules sous-marins. Il serait alors intéressant de pouvoir simuler en même temps la dynamique du solide et celle du fluide. L'idée développée dans cette thèse est d'utiliser la technique Smoothed Particles Hydrodynamics (SPH), qui est très récente et qui modélise le fluide comme un ensemble de particules sans maillage. Afin de valider les résultats de simulations une première étude a été réalisée avec un balancier hydrodynamique. Cette étude a permis la mise au point d'une méthode innovante d'estimation de paramètre hydrodynamique (forces de frottement et masse ajoutée) qui est plus robuste que les méthodes existantes lorsqu'il est nécessaire d'utiliser des dérivées numériques du signal mesuré. Ensuite, l'utilisation de deux types de solveur SPH : Weakly Compressible SPH et Incompressible SPH, est validée en suivant la démarche de validation proposée dans cette thèse. Sont étudiés, premièrement, le comportement du fluide seul, deuxièmement, un cas hydrostatique, et enfin un cas dynamique. L'utilisation de deux méthodes de modélisation de l'interaction fluide-solide : la méthode de réflexion de la pression et la méthode d'extrapolation est étudiée. La capacité d'atteindre une vitesse limite due aux forces de frottement est démontrée. Les résultats d'estimation des paramètres hydrodynamiques à partir des essais de simulation est finalement discutée. La masse ajoutée simulée du solide s'approche de la réalité, mais les forces de frottement semblent actuellement ne pas correspondre à la réalité. Des pistes d'améliorations pour pallier à ce problème sont proposées
This thesis focuses on techniques that allows the simulation of dynamic interactions between an underwater vehicle and the surrounding water. The main objective is to propose a satisfactory solution to be able to test control algorithms and hull shapes for underwater vehicles upstream of the design process. In those cases, it would be interesting to be able to simulate solid and fluid dynamics at the same time. The idea developed in this thesis is to use the Smoothed Particles Hydrodynamics (SPH) technique, which is very recent, and which models the fluid as a set of particles without mesh. In order to validate the simulation results a first study has been performed with a hydrodynamic pendulum. This study allowed the development of an innovative method for estimating the hydrodynamic parameters (friction forces and added mass) which is more robust than previous existing methods when it is necessary to use numerical derivatives of the measured signal. Then, the use of two types of SPH solver: Weakly Compressible SPH and Incompressible SPH, is validated following the validation approach proposed in this thesis. Firstly, the behaviour of the fluid alone is studied, secondly, a hydrostatic case, and finally a dynamic case. The use of two methods for modelling the fluid-solid interaction: the pressure mirroring method and the extrapolation method is studied. The ability to reach a limit velocity due to friction forces is demonstrated. The results of the hydrodynamic parameters estimation from simulation tests are finally discussed. The simulated added mass of the solid approaches reality, but the friction forces currently seem not to correspond to reality. Possible improvements to overcome this problem are proposed

APA, Harvard, Vancouver, ISO, and other styles

36

Cerpa, Gilvonio Nestor. "Interaction lithosphère-manteau en contexte de subduction 3D. Relations entre déformation de surface et processus profonds." Thesis, Nice, 2015. http://www.theses.fr/2015NICE4045/document.

Full text

Abstract:

A l'échelle de plusieurs dizaines de millions d'années, un système de subduction implique de grandes déformations de la plaque plongeante assimilée un solide viscoélastique, et du manteau supérieur assimilé à un fluide newtonien. L'objectif de ce travail est de développer une stratégie de couplage solide-fluide appliquée à l'étude de l'interaction lithosphère-asthénosphère. Cette stratégie est basée sur l'utilisation de maillages non-conformes aux interfaces et d'une méthode de domaines fictifs (MDF) pour la résolution du problème fluide. Pour l'efficience des modèles 3D, nous employons une formulation simplifiée de la méthode de domaines fictifs par multiplicateurs de Lagrange. La MDF développée est validée par des comparaisons avec des solutions analytiques qui montrent que la méthode est d'ordre 1. La stratégie de couplage est également validée par la comparaison avec d'autres méthodes de couplage solide-fluide. Une première étude est ensuite menée pour analyser l'influence de certains paramètres rhéologiques et cinématiques sur la dynamique d'une subduction contrôlée par les vitesses des plaques. Cette étude, en 2D, concerne plus spécifiquement le mécanisme de plissement périodique du slab lorsque celui-ci est ancré à 660 km de profondeur. Ce mécanisme induit des variations de pendage du slab générant des variations de l'état de contrainte de la plaque chevauchante. Un intérêt particulier est porté sur l'influence de la viscosité du manteau sur les plissements. Dans ce cadre, nous réalisons une application à la subduction andine
Over the time scale of tens of millions of years, a subduction system involves large deformations of tectonics plates, as one plate sinks into the Earth's mantle. The aim of this work was to develop a soli-fluid coupling method applied to the lithosphere-asthenosphere interaction in the context of subduction zones. Plates were assumed to behave as viscoelastic bodies, while the upper mantle was assimilated to a newtonian fluid. The method developped here is based on the use of non-matching interface meshes and a fictitious domain method (FDM) for the fluid problem. To optimize the computational efficiency of 3D model, we used a simplified version of the Lagrange multipliers fictitious domain method. The developped FDM has been benchmarked with analytical solutions and we showed that this FDM is a first-order method. The coupling method has also been compared to other fluid-solid coupling methods using matching interfaces meshes. A first two-dimensional study was performed in order to evaluate the influence of some rheological and kinematic parameters on the dynamics of a subduction controlled by the velocity of the plates. This study aimed at investigating cyclic slab folding over a rigid 660 km depth transition zone. This folding mechanism induces variations in slab dip that generate variations in the stress state of the overriding plate. We focussed on the influence of the upper mantle viscosity on slab folding. We also applied this model to the Andean subduction zone. Several studies have determined a cyclic variation of the South-American tectonic regime (period of 30-40~Myrs) which may have been related to the slab dip evolution

APA, Harvard, Vancouver, ISO, and other styles

37

Aharonov, Einat. "Solid-fluid interactions in porous media : processes that form rocks." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/53026.

Full text

APA, Harvard, Vancouver, ISO, and other styles

38

McCorquodale, Mark W. "Interaction between oscillating-grid turbulence and a solid impermeable boundary." Thesis, University of Nottingham, 2018. http://eprints.nottingham.ac.uk/49971/.

Full text

Abstract:

The interaction of a boundary with turbulence is a defining feature of many turbulent flows, resulting in a turbulent boundary layer which plays a prominent role in the production and dissipation of turbulence. Commonly, this interaction is dominated by the effects of mean shear. However, more subtle aspects of the interaction, such as effects associated with turbulent motions impinging onto the boundary, are still thought to play a key role in giving rise to the boundary layer structure. Unfortunately, these aspects of the interaction are currently poorly understood. A better understanding of these aspects of the interaction may be derived by isolating them from the effects of mean shear through the study of zero-mean-shear turbulence interacting with a boundary. This study reports experimental work investigating the interaction between oscillating-grid turbulence (OGT) and a solid impermeable boundary. OGT is a commonly used experimental tool that produces a turbulent flow which is approximately homogeneous and isotropic in planes parallel to the oscillating grid but which is inhomogeneous in planes perpendicular to the oscillating grid. Throughout this study, instantaneous velocity measurements of the flow are obtained by applying two-dimensional particle imaging velocimetry to the vertical plane through the centre of the oscillating grid. A detailed preliminary study to characterise the flow generated by the OGT apparatus is initially performed. Visualisation of the flow close to the oscillating grid indicates that large-scale circulations are induced in OGT by the merging of grid-induced jets close to the tank walls. The installation of an open-ended cuboidal `inner box' below the grid is shown to inhibit the merging of these jets, thereby resulting in a more regular jet structure close to the oscillating grid and a corresponding reduction in mean flow within the inner box. It is also found that, contrary to assumptions in the literature, this amendment to the standard OGT apparatus is most effective when the top of the inner box is located close to the oscillating grid. The reduction in mean flow intensity that results from the use of a correctly installed inner box brings about a turbulent flow in which the mean flow velocity components are small compared to velocity fluctuations, thereby enabling a meaningful comparison to be made with zero-mean-shear turbulence. Consequently, the interaction between OGT and a solid impermeable boundary is studied to derive insight into the mechanisms governing the interaction of zero-mean-shear turbulence with boundaries. Results indicate that a critical aspect of the interaction is the blocking of a boundary-normal flux of turbulent kinetic energy across the boundary-affected region, which acts to increase the magnitude of the boundary-tangential turbulent velocity components, relative to the far-field trend, but not the boundary-normal turbulent velocity component. This feature arises as a result of the anisotropic nature of the flow produced by OGT, whereby the turbulent fluctuations decay with distance normal to and away from the oscillating grid, and would not be present in a turbulent flow that was otherwise homogeneous above the boundary-affected region of the flow. This observation provides new insight into the validity of well-established models of the interaction of zero-mean-shear turbulence and a solid impermeable boundary and provides a physical mechanism that explains the disparity in previously reported measurements relating to this problem. The results reported are also in support of intercomponent energy transfer mechanisms previously proposed to govern the interaction of zero-mean-shear turbulence with boundaries, including viscous and `return-to-isotropy' mechanisms. That is, within a thin region adjacent to the boundary, approximately equal in thickness to the viscous sublayer, the data indicate that turbulent motions incident towards the boundary are more energetic than motions away, which are characteristics of an intercomponent energy transfer primarily driven by the viscous dissipation of turbulent kinetic energy. In addition, at the edge of the boundary-affected region, where the magnitude of the boundary-tangential turbulent velocity components exceeds the magnitude of the boundary-normal turbulent velocity component, results indicate that an intercomponent energy transfer occurs from the boundary-tangential turbulent velocity components to the boundary-normal turbulent velocity component in a so-called `return-to-isotropy' energy transfer. However, the data also indicate the presence of an additional intercomponent energy transfer, from the boundary-normal turbulent velocity component to the boundary-tangential turbulent velocity components over a thin region outside the viscous sublayer. Comparison to previously published results of related studies indicates that this mechanism is also prevalent in previous work, but is not captured within existing models of intercomponent energy transfer at the boundary. Results further indicate that the intercomponent energy transfer mechanisms are not independent of the blocking of the boundary-normal turbulent kinetic energy flux. That is, the blocking of the boundary-normal turbulent kinetic flux promotes anisotropy within the boundary-affected region of the flow and thereby induces a stronger `return-to-isotropy' energy transfer mechanism. Hence, the effect of a solid impermeable boundary on turbulent velocity components in zero-mean-shear turbulence depends critically on the nature of the original turbulent field (i.e. homogeneous or inhomogeneous turbulence).

APA, Harvard, Vancouver, ISO, and other styles

39

Park, Heungsup. "Drop impingement and interaction with a solid surface." Diss., Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/8236.

Full text

APA, Harvard, Vancouver, ISO, and other styles

40

Schiffer, Andreas. "The response of submerged structures to underwater blast." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:4503e2e9-c712-4f8a-a6bb-9986981d56ab.

Full text

Abstract:

The response of submerged structures subject to loading by underwater blast waves is governed by complex interactions between the moving or deforming structure and the surrounding fluid and these phenomena need to be thoroughly understood in order to design structural components against underwater blast. This thesis has addressed the response of simple structural systems to blast loading in shallow or deep water environment. Analytical models have been developed to examine the one-dimensional response of both water-backed and air-backed submerged rigid plates, supported by linear springs and loaded by underwater shock waves. Cavitation phenomena as well as the effect of initial static fluid pressure are explicitly included in the models and their predictions were found in excellent agreement with detailed FE simulations. Then, a novel experimental apparatus has been developed, to reproduce controlled blast loading in initially pressurised liquids. It consists of a transparent water shock tube and allows observing the structural response as well as the propagation of cavitation fronts initiated by fluid-structure interaction in a blast event. This experimental technique was then employed to explore the one-dimensional response of monolithic plates, sandwich panels and double-walled structures subject to loading by underwater shock waves. The performed experiments provide great visual insight into the cavitation process and the experimental measurements were found to be in good agreement with analytical predictions and dynamic FE results. Finally, underwater blast loading of circular elastic plates has been investigated by theoretically modelling the main phenomena of dynamic plate deformation and fluid-structure interaction. In addition, underwater shock experiments have been performed on circular composite plates and the obtained measurements were found in good correlation with the corresponding analytical predictions. The validated analytical models were then used to determine the optimal designs of circular elastic plates which maximise the resistance to underwater blast.

APA, Harvard, Vancouver, ISO, and other styles

41

Niaki, Seyed Reza Amini. "Effects of inter particle friction on the meso-scale hydrodynamics of dense gas-solid fluidized flows." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/18/18147/tde-10122018-165927/.

Full text

Abstract:

Gas-solid fluidized bed reactors are widely applied in chemical and energy industries, and their design and scale-up are virtually empirical, extremely expensive and time consuming. This scenario has motivated the development of alternative theoretical tools, and two-fluid modeling, where gas and particulate are both treated as interpenetrating continuum phases, has appeared as a most promising approach. Owing to the large domains to be resolved in real-scale fluidized bed reactors, only filtered modeling approaches are feasible, and closure models become necessary to recover sub-grid effects that are filtered by the very coarse numerical grids that are imposed owing to computational limitations. Those closure models, which in hydrodynamic formulations account for filtered interphase momentum exchanges and filtered and residual stresses in the phases, can be derived from results of highly resolved simulations (HRS) performed over small size domains under refined numerical grids. One widely practiced approach consists of applying two-fluid modeling under micro-scale defined closures, generally known as microscopic two-fluid modeling. This approach includes microscopic closures for solid phase stresses derived from the kinetic theory of granular flows (KTGF), which accounts for kinetic-collisional effects only, and is adequate to dilute flows. Otherwise, the conventional KTGF does not account for interparticle friction effects, and its application to dense flow conditions is quite questionable. In this work a literature available modified version of KTGF is applied which also accounts for interparticle friction, and highly resolved simulations are performed for dense flow conditions in order to evaluate the effects of friction over relevant filtered parameters (namely effective drag coefficient, filtered and residual stresses). Ranges of domain average solid volume fractions and gas Reynolds numbers are considered (macro-scale conditions) embracing dense gas-solid fluidized flows from suspensions up to pneumatic transport. The MFIX open source code is used in all the simulations, which are performed over 2D periodical domains for a unique monodisperse particulate. The HRS results (i.e. meso-scale flow fields) are filtered over regions compatible with grid sizes in large scale simulations, and the relevant filtered parameters of concern are derived and classified by ranges of other filtered parameters taken as independent variables (filtered solid volume fraction, filtered slip velocity, and filtered kinetic energy of solid velocity fluctuations, which are referred to as markers). Results show that the relevant filtered parameters of concern are well correlated to all of those filtered markers, and also to all of the imposed macro-scale conditions. Otherwise, interparticle friction showed no significant effects over any filtered parameter. It is recognized that this issue clearly requires further investigation notably regarding the suitability of the markers that were assumed for classifying the filtered results. The current work is intended as a contribution for future developments of more accurate closure models for large scale simulations of gas-solid fluidized flows.
Reatores de leito fluidizado de escoamento gás-sólido são largamente utilizados nas indústrias química e de energia, e o seu projeto e escalonamento são virtualmente empíricos, extremamente caros e demorados. Este cenário tem motivado o desenvolvimento de ferramentas teóricas alternativas, e a modelagem de dois fluidos, onde gás e particulado são ambos tratados com fases contínuas interpenetrantes, tem surgido como uma aproximação muito promissora. Devido aos grandes domínios a serem resolvidos em reatores de leito fluidizado de escala real, apenas aproximações de modelagem filtradas são viáveis, e modelos de fechamento tornam-se necessários para recuperar efeitos sub-malha que são filtrados pelas malhas numéricas grosseiras que são impostas devido as limitações computacionais. Estes modelos de fechamento, que em formulações hidrodinâmicas respondem principalmente por trocas de momentum filtradas entre fases e tensões filtradas e residuais nas fases, podem ser obtidos de resultados de simulações altamente resolvidas (SAR) realizadas em domínios de dimensões reduzidas sob malhas numéricas refinadas. Uma aproximação largamente praticada consiste na aplicação de modelagem de dois fluidos sob fechamentos definidos na micro-escala, genericamente conhecida como modelagem microscópica de dois fluidos. Esta aproximação inclui fechamentos microscópicos para tensões da fase sólida obtidos da teoria cinética dos escoamentos granulares (TCEG), que considera apenas efeitos cinéticos-colisionais, e é adequada para escoamentos diluídos. Por outro lado, a TCEG convencional não leva em conta efeitos de fricção interpartículas, e sua aplicação para condições densas de escoamento é bastante questionável. Neste trabalho aplica-se uma versão modificada da TCEG disponível na literatura que também leva em conta fricção interpartículas, e simulações altamente resolvidas são realizadas para condições de escoamentos densos visando avaliar os efeitos da fricção sobre os parâmetros filtrados relevantes (coeficiente de arrasto efetivo, tensões filtradas e residuais). Considera-se faixas de frações volumétricas de sólido e números de Reynolds do gás médios no domínio (condições de macro-escala) abrangendo escoamentos gás-sólido fluidizados densos desde suspensões até transporte pneumático. O código aberto MFIX é utilizado em todas as simulações, que foram executadas sobre domínios periódicos 2D para um único particulado monodisperso. Os resultados das SAR (i.e., campos de escoamento de meso-escala) foram filtrados sobre regiões compatíveis com tamanhos de malha praticados em simulações de grandes escalas, e os parâmetros filtrados relevantes de interesse são calculados e classificados por faixas de outros parâmetros filtrados tomados como variáveis independentes (fração volumétrica de sólido filtrada, velocidade de deslizamento filtrada, e energia cinética das flutuações de velocidade da fase sólida filtrada, que são referidos como marcadores). Os resultados mostram que os parâmetros filtrados relevantes de interesse são bem correlacionados com todos os marcadores, e também com todas as condições de macro-escala impostas. Por outro lado, a fricção interpartículas não mostrou efeitos significativos sobre qualquer parâmetro filtrado. Reconhece-se que este aspecto claramente requer investigações adicionais, notadamente com respeito à adequação dos marcadores que foram considerados para classificação dos resultados filtrados. O trabalho corrente é posto como uma contribuição para o desenvolvimento futuro de modelos de fechamento mais acurados para simulações de grandes escalas de escoamentos gás-sólido fluidizados.

APA, Harvard, Vancouver, ISO, and other styles

42

Zhang, Yonghao. "Particle-gas interactions in two-fluid models of gas-solid flows." Thesis, University of Aberdeen, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.367375.

Full text

Abstract:

Modelling gas-solid two-phase flows using a two-fluid approach has two main difficulties: formulating constitutive laws for the particulate stresses and modelling the gas turbulence modulation. Due to the complex nature of the gas-particle interactions, there is no universal model covering every flow regime. In this thesis, three flow regimes with distinctive characteristics are studied, i.e. the very dense regime where the solid volume fraction, v₂>5%, the dense flow regime where 5%≥1%, and the relatively dilute regime where 1%≥v₂>0.1%. In the very dense flow regime, where the interstitial gas is normally neglected, the gas flow is assumed laminar and causes a viscous energy dissipation in the particulate phase. Numerical results for granular materials flowing down an inclined chute show that the interstitial gas may have a considerable effect in these flows. In the dense regime, where the inter-particle collisions are very important, a fluctuational energy transfer rate between the two phases is postulated, similar to that in a dilute Stokes flow. Consequently, the numerical solutions relax the restriction of elastic inter-particle collisions and show good agreement with experimental measurements. In the above two regimes, the kinetic theory of dry granular flow is adopted for the particulate stresses because the inter-particle collisions dominate the flows. The interstitial gas influence on the constitutive flow behaviour of the particulate phase is considered in the relatively dilute flow regime also, and a k-equation with a prescribed turbulent length scale is first used to address the gas turbulence modulation. Numerical results show that the gas turbulence has a significant effect on the microscopic flow behaviour of the particulate phase. The k-equation of Crowe & Gillandt (1998) has the best performance in predicting the experimentally observed phenomena. Finally, the influence of the particles on the k-^Ε model coefficients are studied and the turbulent motion is considered to be restricted by the particles, thereby reducing the turbulent length scale directly. The simulation results indicate that these coefficients should be modified in order to incorporate the effect of particles.

APA, Harvard, Vancouver, ISO, and other styles

43

Pino, Munoz Daniel Humberto. "High-performance computing of sintering process at particle scale." Phd thesis, Ecole Nationale Supérieure des Mines de Saint-Etienne, 2012. http://tel.archives-ouvertes.fr/tel-00843105.

Full text

Abstract:

Within the general context of solid-state sintering process, this work presents a numerical modeling approach, at the particle scale, of ceramic particle packing consolidation. Typically, the sintering process triggers several mass transport paths that are thermally activated. Among those diffusion paths, the most important ones are: surface diffusion, grain boundary diffusion and volume diffusion. Including this physics into a high-performance computing framework would permit to gain precious insights about the driving mechanisms. The aim of the present work is to develop a model and a numerical strategy able to integrate the different diffusion mechanisms into continuum mechanics framework. In the cases of surface diffusion and volume diffusion, the mass flux is calculated as a function of the surface curvature Laplacian and the hydrostatic pressure gradient, respectively. The physical model describing these two transport mechanisms is first presented within the framework of continuum mechanics. Then the numerical strategy developed for the simulation of the sintering of many particles is detailed. This strategy is based on a discretization of the problem by using a finite element approach coupled with a Level-Set method used to describe the particles free surface. This versatile strategy allows us to perform simulations involving a relatively large number of particles. Furthermore, a mesh adaptation technique allows the particles surface description to be improved, while the number of mesh elements is kept reasonable. Several 3D simulations, performed in a parallel computing framework, show the changes occurring in the structure of 3D granular stacks.

APA, Harvard, Vancouver, ISO, and other styles

44

Biamino, Laurent. "Etude expérimentale de l'interaction d'une onde de choc avec une structure mobile autour d'un axe." Thesis, Aix-Marseille 1, 2011. http://www.theses.fr/2011AIX10093/document.

Full text

Abstract:

Ce travail de thèse s’appuie sur une étude expérimentale en tube à choc, plus précisément, c’est une approche expérimentale de l'étude de l'interaction fluide-structure. Considérons un solide indéformable auquel on laisse un degré de liberté en rotation autour d'un axe. Cette structure ferme un espace clos. Si le contenu de l'espace clos subit le passage d'une onde de choc, ce solide va être mis mouvement et tourner autour de son axe. Concrètement, l'onde de choc va augmenter les caractéristiques physiques, en particulier sa pression, du fluide en contact avec la face impactée de cette porte. La face opposée de la porte ne subissant pas ou que très peu l'influence de l'onde de choc, une seule de ses faces est soumise à la surpression. Au moment de l'impact, le déséquilibre ainsi créé impose une action mécanique sur la porte qui va la faire accélérer et tourner autour de son axe de rotation. Jusqu'à ce stade tout est relativement simple. La difficulté intervient à l'instant où la porte commence à s'ouvrir, car les frontières du volume dans lequel le fluide évolue sont modifiées. Des fuites apparaissent et le gaz qui était maintenu dans un volume clos peut maintenant s'écouler vers un milieu libre. Une communication entre les gaz agissant de chaque coté de la porte est créée modifiant leurs propriétés et par conséquent la pression agissant sur chaque côté de la porte. Les actions mécaniques qui s'appliquent sur la porte ne sont plus les mêmes, et par conséquent l'accélération que la porte subit aussi. Au fur et à mesure que la porte change de position, le problème fluide continue d'être modifié et change en retour son action sur la porte. Cette interaction perdure soit jusqu'à ce que les limites du problème cessent d'être modifiées, la porte ne peut plus bouger, ou bien lorsque les actions mécaniques agissant sur la porte s'équilibrent, les fluides de chaque côté de la porte étant dans le même état physique. Le travail présenté ici est une étude des paramètres du fluide ou du solide en mouvement qui sont les acteurs de la loi comportementale gérant ce système complexe. Pour ce faire, nous avons réalisé une maquette expérimentale mettant en action la physique que nous venons de décrire et nous l'avons adaptée à un tube à choc. En éprouvant de nombreuses configurations expérimentales, nous avons pu déterminer comment l'écoulement interne d'un tube à choc évolue lorsqu'il est plus ou moins ouvert à son extrémité. Comment une porte fermée réagit-elle à l'impact d'une onde de choc et quelles en sont les conséquences sur l'évolution des fluides mis en jeu? Quelles sont les conséquences d'une position différente de la porte au moment de l'impact avec l'onde de choc? Ou encore, quel rôle joue l'intensité de l'onde de choc incidente ou l'inertie de la porte sur toute cette dynamique?
This thesis is based on an experimental study carried out in shock tube; in particular, this is an experimental approach to the study of fluid-structure interaction. Consider a rigid body which is allowed to rotate only around an axis and which closes a confined space. If a shock wave crosses the content of the confined space, the body will accelerate and rotate around its axis. Specifically, the shock wave will increase the physical characteristics, especially its pressure, of the fluid acting on the impacted face of the door. The opposite side of the door is not influenced by the incident shock wave, only one of its faces is subjected to overpressure. Following the first impact, the resulting imbalance imposes a mechanical action on the door that will increase its speed and make it turn around its rotation axis. The difficulty comes when the door begins to open: the volume boundaries in which the fluid is contained are modified. Leaks occur and the gas kept in this closed volume can now flow to the atmosphere. Communication between the gas acting on each side of the door is created modifying their properties and consequently the pressure acting on each side of the door.The mechanical actions that apply to the door are no more the same with time, and therefore the acceleration of the door is changing. As the door moves, the fluid problem continues to be changed and in turn it changes its action on the door. This interaction process continues until either the limits of the problem ceases to be changed, the door cannot move, or when the mechanical actions acting on the door are in equilibrium, fluids on each side of the door are in the same physical state. The presented work is a study of the parameters of the fluid or the solid motion which are main actors in the behavioral law managing this complex system. In this aim, we designed an experimental device involving the physics that we have described and we have adapted it to a shock tube. Testing many experimental configurations, we could determine how the internal flow of a shock tube evolves when the end of this shock tube is more or less open.How a closed door reacts to the impact of a shock wave and what are the implications for the evolution of the involved fluids? What are the consequences of a different position of the door at the instant of the impact with the incident shock wave? What role plays the intensity of the incident shock wave or the inertia of the door on this dynamic?

APA, Harvard, Vancouver, ISO, and other styles

45

Mutch, Greg Alexander. "Carbon capture and storage optimisation in solid oxides : understanding surface-fluid interactions." Thesis, University of Aberdeen, 2016. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=231044.

Full text

Abstract:

To decrease carbon dioxide emissions into the atmosphere for climate change mitigation it is necessary to modify existing practices in processes where greenhouse gases are emitted. Due to the extremely large volumes of carbon dioxide produced globally, it is generally accepted that although carbon dioxide conversion and utilisation will contribute in the long term, in the short to medium term it will be necessary to capture and store carbon dioxide emissions to progress towards a low carbon future. Current industrial capture processes incur large energy and thus economic penalties. Storage in geological formations requires robust confidence in storage security to be publically accepted. Therefore the objective of this work was to study carbon dioxide capture and storage in processes directly confronting these two major challenges. Carbon dioxide adsorption on oxide materials for advanced carbon capture processes with lower energetic and economic penalties was investigated. Water was shown to play a crucial role in determining the presence of reactive sites, the speciation of carbonates formed and increased sorbent utilisation. A high surface area oxide with specifically exposed facets was prepared and the impact of these facets on carbon dioxide uptake performance was assessed. Volumetric gas adsorption and isotherm modelling supported the presence of two distinct adsorption sites. To enhance confidence in storage security it is necessary to understand storage processes that result in stable products. An apparatus capable of obtaining geological storage conditions was developed and carbonate formation and surface hydration at high pressure was investigated. By locating individual reactive cations on the surface of silica, silicate mineral analogues were prepared. It was shown that carbonate speciation was dependent on the reactive cation and the presence or absence of water.

APA, Harvard, Vancouver, ISO, and other styles

46

Michelin, Sébastien Honoré Roland. "Falling, flapping, flying, swimming,... high-Re fluid-solid interactions with vortex shedding /." Diss., [La Jolla] : University of California, San Diego, 2009. http://wwwlib.umi.com/cr/ucsd/fullcit?p3369655.

Full text

Abstract:

Thesis (Ph. D.)--University of California, San Diego, 2009.
Title from first page of PDF file (viewed September 17, 2009). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 200-210).

APA, Harvard, Vancouver, ISO, and other styles

47

Zhao, Shunzi. "The numerical study of fluid-solid interactions for modelling blood flow in arteries." Thesis, City University London, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.312951.

Full text

APA, Harvard, Vancouver, ISO, and other styles

48

Persson, Eva. "Drug Dissolution under Physiologically Relevant Conditions In Vitro and In Vivo." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis : Universitetsbiblioteket [distributör], 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-7195.

Full text

APA, Harvard, Vancouver, ISO, and other styles

49

Coudouel, Guillaume. "Toward a numerical predictive method based on fatigue analysis for droplet impingement erosion." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSEI101/document.

Full text

Abstract:

Le but du travail présenté est la compréhension puis la simulation numérique des mécanismes d'érosion des augets de turbine Pelton par impacts répétés de gouttes d'eau dans le but de prédire la durée de vie des composants. Tout d'abord, les phénomènes de propagation d'ondes dans les milieux fluide et solide sont étudiés. Cela permet de mettre en lumière l'évolution temporelle et la distribution spatiale des pressions de contact, et l'apparition de microjets par éjection supersonique du fluide au contact. Les études expérimentales de l'érosion par gouttes d'eau traduisent un dommage basé sur la fissuration par fatigue. Des simulations numériques en dynamique rapide couplées fluide-structure sont alors effectuées. Le domaine solide est discrétisé par la Méthode des éléments Finis (MEF), et le domaine fluide par la méthode Smoothed Particle Hydrodynamics (SPH), qui est une méthode particulaire (sans maillage) particulièrement adaptée aux grandes distorsions et au suivi des surfaces libres. L'analyse des états de contraintes vient corroborer la nature cyclique de l'endommagement. La simulation d'érosion est alors réalisée à l'aide de critères de fatigue multiaxiaux. Le choix se porte vers un premier critère général de l'American Society of Mechanical Engineers (ASME), utilisant les valeurs principales des différences de contraintes au cours du temps. Le second choix concerne un critère à plan critique : le critère de Dang Van 2. Il traite séparément la contrainte hydrostatique et le cisaillement alterné maximal local. Ces critères permettent de définir les régions érodées du solide au bout d'un nombre d'impact donné, ce qui fait de cette démarche une méthode prédictive. Une étude paramétrique pour différentes tailles de gouttes et vitesses d'impact est ensuite réalisée, puis on évalue l'influence de la présence d'une couche de coating
The goal of this work is the comprehension and the numerical simulation of erosion caused by repeated droplet impact on Pelton turbine buckets, to predict the lifetime of these components. First, waves propagation phenomenon inside fluid and solid domains are presented, which allows determining the time evolution and spatial distribution of contact pressure, and the birth of lateral microjets by supersonic ejection of the fluid on the contact. Experimental studies of erosion by droplet impact highlight a fatigue cracking-based erosion mechanism. Then, coupled FSI computation are performed. The solid subdomain is discretized by the Finite Element Method (FEM), and the fluid subdomain by the Smoothed Particle Hydrodynamics (SPH), which is a particle method (meshless) effectively recommended for large distortions and free surface tracking. Stress analysis confirms the cyclic nature of the damage mechanism, and erosion simulation is performed using multiaxial fatigue criteria. The first selected criterion is a general one from the American Society of Mechanical Engineers (ASME) using principal values of stress differences over time. The second one is the Dang van 2 criterion, belonging to the family of critical plane criteria. This criterion considers separately the effects due to hydrostatic stress on one hand, and the ones induced by maximum local shear on the other. These two criteria are used to building the equivalent eroded zones of the solid subdomain for a given number of impacts, which allows to qualify this procedure as a predictive predictive. Finally, a parametric study for different droplet sizes and velocites is computed, and the effects of a coating layer are investigated

APA, Harvard, Vancouver, ISO, and other styles

50

Gnanasambandham, Chandramouli [Verfasser]. "Particle Dampers- Enhancing Energy Dissipation using Fluid/Solid Interactions and Rigid Obstacle-Grids / Chandramouli Gnanasambandham." Düren : Shaker, 2021. http://d-nb.info/124085367X/34.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Dissertations / Theses on the topic 'Solid-fluid interaction'

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles