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Tesi sul tema "Gas dynamics computer simulation"
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1
Zhao, Yong. "Computer simulation of gas dynamics in engine manifolds". Thesis, University of Manchester, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318589.
Testo completo
2
Foster, P. A. "The computer simulation of the gas dynamics in ring galaxy formation". Thesis, University of Manchester, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.375065.
Testo completo
3
Lyons, Eric P. "Computer simulation of poly(ethylene terephthalate) and derivatives structure and their ramifications for gas transport". Thesis, Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/11039.
Testo completo
4
JUNG, JANGWOOK PHILIP. "Computer Simulation of Transport of Small Molecules Through a Gas Channel Embedded in a Phospholipid Bilayer". University of Cincinnati / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1131054184.
Testo completo
5
Shukla, Charu L. "Computationally Probing the Cybotactic Region in Gas-Expanded Liquids". Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/14510.
Testo completoAbstract (sommario):
Gas-expanded liquids (GXLs) are novel and environmentally benign solvent systems with applications in reactions, separations, nanotechnology, drug delivery, and microelectronics. GXLs are liquid mixtures consisting of an organic solvent combined with a benign gas, such as CO2, in the nearcritical regime. In this work, molecular dynamics simulations have been combined with experimental techniques to elucidate the cybotactic region or local environment in gas-expanded liquids. Molecular dynamics simulations show clustering of methanol molecules in carbon dioxide-methanol mixtures. This clustering was not observed in carbon dioxide-acetone mixtures. Furthermore, addition of carbon dioxide enhances diffusivity of solutes in gas-expanded media as shown by both simulations and Taylor-Aris dispersion experiments. Finally, local structure and local compositions around pyrene in carbon dioxide-methanol and carbon-dioxide acetone were investigated using simulations and UV-vis spectroscopy.
6
Gohres, John Linton III. "Spectroscopic and computational investigations of molecular interactions in gas-expanded liquids". Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/24692.
Testo completoAbstract (sommario):
Thesis (Ph.D.)--Chemical Engineering, Georgia Institute of Technology, 2008.Committee Chair: Charles A. Eckert; Committee Co-Chair: Charles L. Liotta; Committee Member: J. Carson Meredith; Committee Member: Rigoberto Hernandez; Committee Member: William J. Koros
7
Pinilla, Castellanos Carlos Celimo. "Computer simulation studies of the structure and dynamics of gas, liquid and solid phases of complex ionic liquids". Thesis, Queen's University Belfast, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.479393.
Testo completo
8
Hendricks, Todd B. "An investigation into computer simulation of the dynamic response of a gas turbine engine". Springfield, Va. : Available from National Technical Information Service, 1997. http://handle.dtic.mil/100.2/ADA328006.
Testo completo
9
Johnson, Perry L. "Toward increasing performance and efficiency in gas turbines for power generation and aero-propulsion unsteady simulation of angled discrete-injection coolant in a hot gas path crossflow". Honors in the Major Thesis, University of Central Florida, 2011. http://digital.library.ucf.edu/cdm/ref/collection/ETH/id/444.
Testo completoAbstract (sommario):
This thesis describes the numerical predictions of turbine film cooling interactions using Large Eddy Simulations. In most engineering industrial applications, the Reynolds-Averaged Navier-Stokes equations, usually paired with two-equation models such as k-Greek lowercase letter epsilon] or k-Greek lowercase letter omega], are utilized as an inexpensive method for modeling complex turbulent flows. By resolving the larger, more influential scale of turbulent eddies, the Large Eddy Simulation has been shown to yield a significant increase in accuracy over traditional two-equation RANS models for many engineering flows. In addition, Large Eddy Simulations provide insight into the unsteady characteristics and coherent vortex structures of turbulent flows. Discrete hole film cooling is a jet-in-cross-flow phenomenon, which is known to produce complex turbulent interactions and vortex structures. For this reason, the present study investigates the influence of these jet-crossflow interactions in a time-resolved unsteady simulation. Because of the broad spectrum of length scales present in moderate and high Reynolds number flows, such as the present topic, the high computational cost of Direct Numerical Simulation was excluded from possibility.B.S.M.E.
Bachelors
Engineering and Computer Science
Mechanical Engineering
10
Ha, Oai The. "Modeling and Numerical Investigation of Hot Gas Defrost on a Finned Tube Evaporator Using Computational Fluid Dynamics". DigitalCommons@CalPoly, 2010. https://digitalcommons.calpoly.edu/theses/400.
Testo completoAbstract (sommario):
Defrosting in the refrigeration industry is used to remove the frost layer accumulated on the evaporators after a period of running time. It is one way to improve the energy efficiency of refrigeration systems. There are many studies about the defrosting process but none of them use computational fluid dynamics (CFD) simulation. The purpose of this thesis is (1) to develop a defrost model using the commercial CFD solver FLUENT to simulate numerically the melting of frost coupled with the heat and mass transfer taking place during defrosting, and (2) to investigate the thermal response of the evaporator and the defrost time for different hot gas temperatures and frost densities. A 3D geometry of a finned tube evaporator is developed and meshed using Gambit 2.4.6, while numerical computations were conducted using FLUENT 12.1. The solidification and melting model is used to simulate the melting of frost and the Volume of Fluid (VOF) model is used to render the surface between the frost and melted frost during defrosting. A user-defined-function in C programming language was written to model the frost evaporation and sublimation taking place on the free surface between frost and air. The model was run under different hot gas temperatures and frost densities and the results were analyzed to show the effects of these parameters on defrosting time, input energy and stored energy in the metal mass of the evaporator. The analyses demonstrate that an optimal hot gas temperature can be identified so that the defrosting process takes place at the shortest possible melting time and with the lowest possible input energy.
11
Makgata, Katlego Webster. "Computational analysis and optimisation of the inlet system of a high-performance rally engine". Diss., Pretoria : [s.n.], 2005. http://upetd.up.ac.za/thesis/available/etd-01242006-123639.
Testo completo
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Bastos, Jaci Carlo Schramm Camara. "Simulação do escoamento gas-solido em um duto cilindrico vertical em leito fluidizado rapido aplicando a tecnica CFD". [s.n.], 2005. http://repositorio.unicamp.br/jspui/handle/REPOSIP/266327.
Testo completoAbstract (sommario):
Orientador: Milton MoriDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica
Made available in DSpace on 2018-09-11T21:07:59Z (GMT). No. of bitstreams: 1 Bastos_JaciCarloSchrammCamara_M.pdf: 4360168 bytes, checksum: 100c57a7c93213cf37fcdab4ee05e24f (MD5) Previous issue date: 2005
Resumo: A presente pesquisa apresenta a modelagem matemática e a simulação de uma operação de fluidização rápida em um longo duto cilíndrico vertical, operação importante em vários processos industriais, sendo que sua principal aplicação está vinculada ao craqueamento catalítico do petróleo para a conversão em gasolina. Tem como objetivos a obtenção de uma compreensão contínua e o conhecimento do desenvolvimento do escoamento gás-sólido, bem como a soma de experiências às pesquisas em escala industrial motivados pela possível predição do desempenho deste tipo de escoamento. O modelo tridimensional, turbulento e bifásico usado para a predição do escoamento gás-sólido, consiste num conjunto de equações de conservação da massa e momento para cada uma das fases, formuladas seguindo a aproximação Euleriana-Euleriana. As variáveis fluidodinâmicas foram estimadas pela solução do modelo, com o emprego de correlações empíricas da literatura e disponibilizadas pelo código computacional de CFD, para garantir o fechamento do modelo e sua solução numérica. Desde de que a predição da dinâmica do escoamento complexo, em dutos com alto fluxo ascendente de sólidos não é possível por meio somente de equações fundamentais, a maioria dos modelos requerem entradas empíricas, as quais somente são adquiridas com a experimentação. Estes dados foram obtidos dos estudos de PÄRSSINEN e ZHU (2001). A geometria e a malha numérica estrutural do duto vertical foram geradas pelo software (CAD) ICEM, subdividido em DDN (geometria) e Hexa (malha). A adaptação do modelo matemático para a geração do modelo numérico foi alcançada com o uso do simulador comercial CFX 5.7. Os resultados obtidos foram avaliados com respeito à teoria apresentada ao longo da dissertação, sendo finalmente feita uma comparação entre as predições numéricas com o modelo e dados experimentais da literatura
Abstract: The present research presents the mathematical modeling and the simulation of an operation of fast fluidization in a long vertical cylindrical duct line, which is an important operation in many industrial processes, where its main application is tied with the catalytic cracking of oil for gasoline synthesis. It has as objective the attainment of a continuous understanding and knowledge of the development of the gas-solid flow, as well as adding of experiences to research of industrial scale equipments motivated by the possibility of prediction of the performance of this type of flow. The three-dimensional, turbulent and two-phase model used for the prediction of the gas-solid flow, consists of a set of conservation equations of mass and momentum for each phase, which was formulated following the Eulerian-Eulerian approach. The fluid dynamics variables was estimated by the solution of the model with the use of correlations found in the literature and available in the computational CFD code, in order to guarantee the closure of the model and its numerical solution. Since the prediction of the dynamics of the complex flow in ducts with high ascending solid flow is not possible by solely using the basic equations, the majority of the models require the setting empirical, parameters which are acquired only with experimentation. These data were obtained from the studies of PÄRSSINEN and ZHU (2001). The geometry and the structural numerical mesh of the vertical duct was generated by the software (CAD) ICEM, subdivided in DDN (geometry) and Hexa (meshing). The adaptation of the mathematical model for the numerical model generation was reached with the use of the commercial simulator CFX 5.7. The results were evaluated with respect to the theory presented along this dissertation, where comparisons between the numerical predictions with the model and experimental data from the literature were performed.
Mestrado
Desenvolvimento de Processos Químicos
Mestre em Engenharia Química
13
Abbasi, Baharanchi Ahmadreza. "Development of a Two-Fluid Drag Law for Clustered Particles Using Direct Numerical Simulation and Validation through Experiments". FIU Digital Commons, 2015. http://digitalcommons.fiu.edu/etd/2489.
Testo completoAbstract (sommario):
This dissertation focused on development and utilization of numerical and experimental approaches to improve the CFD modeling of fluidization flow of cohesive micron size particles. The specific objectives of this research were: (1) Developing a cluster prediction mechanism applicable to Two-Fluid Modeling (TFM) of gas-solid systems (2) Developing more accurate drag models for Two-Fluid Modeling (TFM) of gas-solid fluidization flow with the presence of cohesive interparticle forces (3) using the developed model to explore the improvement of accuracy of TFM in simulation of fluidization flow of cohesive powders (4) Understanding the causes and influential factor which led to improvements and quantification of improvements (5) Gathering data from a fast fluidization flow and use these data for benchmark validations. Simulation results with two developed cluster-aware drag models showed that cluster prediction could effectively influence the results in both the first and second cluster-aware models. It was proven that improvement of accuracy of TFM modeling using three versions of the first hybrid model was significant and the best improvements were obtained by using the smallest values of the switch parameter which led to capturing the smallest chances of cluster prediction. In the case of the second hybrid model, dependence of critical model parameter on only Reynolds number led to the fact that improvement of accuracy was significant only in dense section of the fluidized bed. This finding may suggest that a more sophisticated particle resolved DNS model, which can span wide range of solid volume fraction, can be used in the formulation of the cluster-aware drag model. The results of experiment suing high speed imaging indicated the presence of particle clusters in the fluidization flow of FCC inside the riser of FIU-CFB facility. In addition, pressure data was successfully captured along the fluidization column of the facility and used as benchmark validation data for the second hybrid model developed in the present dissertation. It was shown the second hybrid model could predict the pressure data in the dense section of the fluidization column with better accuracy.
14
Lion, Thomas. "Osmosis : a molecular dynamics computer simulation study". Thesis, University of Edinburgh, 2013. http://hdl.handle.net/1842/7877.
Testo completoAbstract (sommario):
Osmosis is a phenomenon of critical importance in a variety of processes ranging from the transport of ions across cell membranes and the regulation of blood salt levels by the kidneys to the desalination of water and the production of clean energy using potential osmotic power plants. However, despite its importance and over one hundred years of study, there is an ongoing confusion concerning the nature of the microscopic dynamics of the solvent particles in their transfer across the membrane. In this thesis the microscopic dynamical processes underlying osmotic pressure and concentration gradients are investigated using molecular dynamics (MD) simulations. I first present a new derivation for the local pressure that can be used for determining osmotic pressure gradients. Using this result, the steady-state osmotic pressure is studied in a minimal model for an osmotic system and the steady-state density gradients are explained using a simple mechanistic hopping model for the solvent particles. The simulation setup is then modified, allowing us to explore the timescales involved in the relaxation dynamics of the system in the period preceding the steady state. Further consideration is also given to the relative roles of diffusive and non-diffusive solvent transport in this period. Finally, in a novel modi cation to the classic osmosis experiment, the solute particles are driven out-of-equilibrium by the input of energy. The effect of this modi cation on the osmotic pressure and the osmotic ow is studied and we find that active solute particles can cause reverse osmosis to occur. The possibility of defining a new "osmotic effective temperature" is also considered and compared to the results of diffusive and kinetic temperatures.
15
Webster, Richard E. "Computer simulation of confined liquid crystal dynamics". Thesis, Sheffield Hallam University, 2001. http://shura.shu.ac.uk/20509/.
Testo completoAbstract (sommario):
Results are presented from a series of simulations undertaken to determine whether dynamic processes observed in device-scale liquid crystal cells confined between aligning substrates can be simulated in a molecular system using parallel molecular dynamics of the Gay-Berne model. In a nematic cell, on removal of an aligning field, initial near-surface director relaxation can induce flow, termed 'backflow', in the liquid. This, in turn, can cause director rotation, termed 'orientational kickback', in the centre of the cell. Simulations are performed of the relaxation in nematic systems confined between substrates with a common alignment on removal of an aligning field. Results show that relaxation timescales of medium sized systems are accessible. Following this, simulations are performed of relaxation in hybrid aligned nematic systems, where each surface induces a different alignment. Flow patterns associated with director reorientation are observed. The damped oscillatory nature of the relaxation process suggests that the behaviour of these systems is dominated by orientational elastic forces and that the observed director motion and flow do not correspond to the macroscopic processes of backflow and kickback. Chevron structures can occur in confined smectic cells which develop two domains of equal and opposite layer tilt on cooling. Layer tilting is thought to be caused by a need to reconcile a mismatch between bulk and surface smectic layer spacing. Here, simulations are performed of the formation of structures in confined smectic systems where layer tilt is induced by an imposed surface pretilt. Results show that bookshelf, chevron and tilted layer structures are observable in a confined Gay-Berne system. The formation and stability of the chevron structure are shown to be influenced by surface slip.
16
Au, Harold (Harold S. ). "Molecular dynamics simulation of nanoporous graphene for selective gas separation". Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/78180.
Testo completoAbstract (sommario):
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2012.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 71-76).
Graphene with sub-nanometer sized pores has the potential to act as a filter for gas separation with considerable efficiency gains compared to traditional technologies. Nanoporous graphene membranes are expected to yield high selectivity through molecular size exclusion effects, while achieving high permeability due to the very small thickness of graphene. In this thesis, we model the separation of gas components from a mixture using a graphene sheet with engineered pores of different sizes. We employ molecular dynamics simulations to calculate a large number of molecular trajectories, and thus obtain low-statistical-uncertainty estimates of transport rates through the membrane. Simulations are performed on two different gas mixtures - a helium-sulfur hexafluoride mixture, for which the large difference in molecular size lends itself to a size-based separation approach, and a hydrogen-methane mixture, which is relevant to natural gas processing. Our simulations show that graphene membranes with large pores are permeable to both gases in the mixture. As pore sizes are reduced, we observe a greater decrease in the permeability of the larger species that results in a molecular size exclusion effect for a range of pore sizes that are still permeable to the smaller species. This indicates that a pore size can be determined that achieves high selectivity in gas separation, while exhibiting high permeability for the desired gas species. We expect this work to form the basis for the design of an energy-efficient graphene-based gas separation device. The simulation-based approach described here can be very useful for guiding experimental efforts which are currently limited by the difficulty associated with creating pores of a specific size in otherwise pristine graphene.
by Harold Au.
S.M.
17
Van, den Bergh Jan-Sjoerd. "Effects of friction and gas modelling on vehicle dynamics simulation". Diss., University of Pretoria, 2014. http://hdl.handle.net/2263/56116.
Testo completoAbstract (sommario):
Validated simulation models have become ever more important in the current technological and economic environment, where simulation is an integral part of the design process. In the field of vehicle dynamics, it is no different, where vehicle manufacturers and researchers are relying more heavily on simulation than ever before. In the competitive field of research and development, the phrase as accurate as possible, as complex as is necessary rings true for vehicle models. Due to the as complex as necessary approach, many complex phenomena such as suspension kinematics and suspension friction remain un-modelled, as the assumption is made that the effects are negligible. The seemingly negligible effects negatively affect the validity of simulation models, especially when deviating from the specific manoeuvre for which the model was originally created.
In this study, focussed on a vehicle with a hydropneumatic suspension system, the effect of gas modelling methodology, friction, and friction modelling strategy on the validity the suspension unit characteristics, and a full non-linear vehicle dynamics model is presented. The approach to gas modelling included three permutations of the ideal gas formulation, namely isothermal, adiabatic, and a heat transfer dependent thermal time-constant approach. The effects of friction were accounted for using a rudimentary lookup table approach, a LuGre, and a Modified LuGre friction model, while using the case where friction is neglected as reference.
The results showed that the gas modelling approach, and the effects of friction, each have a significant effect on model accuracy and validity when compared to physical test results. The improvement is witnessed on both the single suspension unit characteristic as well as on the full non-linear simulation model. This effectively proves that seemingly negligible effects may have a significant effect on model validity.Gevalideerde simulasie modelle word al hoe meer belangrik in die huidige tegnologiese en ekonomiese omgewing, waar simulasie as n integrale deel van die ontwerp prosess is. In die voertuig-dinamika veld is dit ook die geval, waar vervaardigers en navorsers meer op simulase staatmaak as ooit tevore. In die navorsings en ontwikkelings veld met sy strawwe kompetisie, word die frase so akkuraat moontlik, so kompleks as nodig dikwels ter harte geneem met die ontwikkeling van voertuig modelle. Die so kompleks as nodig benadering het die gevolg dat baie verskynsels soos suspensie kinematika en wrywing nie in ag geneem word nie, aangesien daar aanvaar word dat die effekte weglaatbaar klein is. Hierdie oënskynlikke weglaatbare effekte, het n negatiewe impak op die akkuraatheid en geldigheid van die model waneer daar afgewyk word van maneuvers waarvoor die model oorspronklik ontwikkel is. In hierdie studie, waar gefokus word op n voertuig met n hidro-pneumatiese suspensie stelsel, word die effek van gas modelering, wrywing, en wrywings modelering strategie op die geldigheid van die suspensie eenheid karakterestieke, asook die vol nie-linieêre voertuig model voorgelê. Die benadering tot gas modelering sluit drie permutasies van die ideale gas wet in, naamlik isotermies, adiabaties, en die hitte-oordrag afhanklikke termiese tyd-konstante formulering. Die effekte van wrywing is op drie maniere in ag geneem, naamklik n opsoek matriks, n LuGre, en n Aangepaste LuGre wrywings model, terwyl die geval waar wrywing weggelaat is gebruik word as verwysing. Die resultate wys dat die gas modelerings strategie, asook die effek van wrywing elkeen n waarneembare effek op die model akkuraatheid en geldigheid het waneer dit vergelyk word met fisiese toets resultate. n Verbetering is gesien in die enkel suspensie eenheid karakterestiek sowel as die vol nie-linieêre simulasie model. Dit bewys effektief dat sekere verskynsels, alhoewel dit klein is in vergelyking met ander effekte, n groot impak op model geldigheid en akkuraatheid kan hê.
Dissertation (MEng)--University of Pretoria, 2014.
tm2016
Mechanical and Aeronautical Engineering
MEng
Unrestricted
18
McBride, Carl. "Computer simulation of liquid crystals". Thesis, Durham University, 1999. http://etheses.dur.ac.uk/4588/.
Testo completoAbstract (sommario):
Molecular dynamics simulation performed on modern computer workstations provides a powerful tool for the investigation of the static and dynamic characteristics of liquid crystal phases. In this thesis molecular dynamics computer simulations have been performed for two model systems. Simulations of 4,4'-di-n-pentyl-bibicyclo[2.2.2]octane demonstrate the growth of a structurally ordered phase directly from an isotropic fluid. This is the first time that this has been achieved for an atomistic model. The results demonstrate a strong coupling between orientational ordering and molecular shape, but indicate that the coupling between molecular conformational changes and molecular reorientation is relatively weak. Simulations have also been performed for a hybrid Gay-Berne/Lennard-Jones model resulting in thermodynamically stable nematic and smectic phases. Frank elastic constants have been calculated for the nematic phase formed by the hybrid model through analysis of the fluctuations of the nematic director, giving results comparable with those found experimentally. Work presented in this thesis also describes the parameterisation of the torsional potential of a fragment of a dimethyl siloxane polymer chain, disiloxane diol (HOMe(_2)Si)(_2)O, using ab initio quantum mechanical calculations.
19
Bates, Martin Alexander. "Computer simulation of liquid crystals". Thesis, University of Southampton, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243183.
Testo completo
20
Lindberg, Maria. "Computer simulations of electronic energy transfer and a molecular dynamics study of a decapeptide". Doctoral thesis, Umeå universitet, Kemiska institutionen, 1991. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-118929.
Testo completoAbstract (sommario):
Electronic energy transfer has been investigated in pure donor systems by means of computer simulations. Calculated properties were the probability that the initially excited donor is excited at a time t after the excitation, Gs(t), the mean square displacement of the excitation and different fluorescence observables. For three dimensional systems the results obtained by Monte Carlo simulations were compared to the so-called GAF-theory {Gouchanour,C. R., Andersen, H. C. and Fayer, M. D., J. Chem. Phys. 81, 4380 (1984)}, and the agreement was found to be good. Anisotropic systems, i.e. mono-, bi- and multilayer systems, were compared to the two-particle model {Baumann,J. and Fayer, M. D., J. Chem. Phys. 85, 4087 (1986)}. The agreement between the Gs(t) calculated from the tp- model and the Monte Carlo simulations were good for all systems investigated. However, the agreement between the fluorescence observables obtained by MC and the tp-model were in general poor. A much better agreement was found when a phenomenological approach was used for calculating the fluorescence depolarization ratios. Three dimensional systems where the donors are rotating on the same time scale as the energy transfer takes place have also been studied and compared to analytical theories. The Molecular Dynamics simulations of decapeptide H142 shows that simulations in a continuum with a relative permeability do not provide a reliable alternative to simulations with explicit solvent molecules.Diss. (sammanfattning) Umeå : Umeå universitet, 1991, härtill 5 uppsatser
digitalisering@umu
21
Taflin, David E. "Numerical simulation of unsteady hypersonic chemically reacting flow /". Thesis, Connect to this title online; UW restricted, 1995. http://hdl.handle.net/1773/9967.
Testo completo
22
Kwan, Stephen. "Computer simulation of arcs in gas-blast circuit-breakers". Thesis, University of Liverpool, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243202.
Testo completo
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Whitley, David Martin. "Computer simulation of polymer permeability and segmental dynamics". Thesis, University of Leeds, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.581955.
Testo completoAbstract (sommario):
The gas transport properties of cis-1,4-polybutadiene (PBD) [1], atactic poly- propylene (PP) [2], polyethylene terephthalate (PET) [3], and polyisobutylene (PIB) [4] have been investigated using molecular dynamics simulations. The two novel film cell methodologies of Kikuchi et al. were investigated, with KKF1 [5] being designed to probe the solubility directly, and KKF2 [6] probing per- meability. Both were also capable of estimating diffusivity. The results of these film cell simulations were compared to the results of traditional gas permeation simulations carried out using bulk samples of PBD, PP, and PET. Analysis of simulation results was mainly via inter-comparison between different polymers, gases, and simulation methodologies. The three different methods showed reasonable agreement in terms of their solubility and diffusivity estimates. Each simulation methodology was found to have its own benefits and shortcomings, with both of the novel film cells having specific challenges in their use. The KKF1 method was found to be simpler to apply than KKF2, and to provide solubility and diffusivity values with smaller uncertainties, meaning that it was the KKF1 model that was chosen to investigate the interesting gas transport properties of polyisobutylene. Using the KKF1 method, molecular dynamics simulations were able to reproduce the order of magnitude difference in the permeability of PIB when compared to PBD. In addition to the gas transport investigation, the local segmental dynamics of PBD, PP, and PET were investigated. Autocorrelation functions of chord vectors spanning different numbers of backbone bonds were calculated, with the CONTIN [7, 8] algorithm being used to find the corresponding distributions of relaxation times. All distributions of relaxation times showed a peak on short time scales, thought to correspond to short length scale segmental motion, and a long time scale peak, thought to correspond to global chain relaxation dynamics. As longer length scale chord vectors were investigated a third peak appeared, temporally located intermediate between the other two peaks. Investigating the temperature dependence of the peaks' characteristic time scale showed that the intermediate and long time scale processes shared identical activation energies, which could infer that they share a common source.
24
Roy, Tuhin Kumar. "The computer simulation of dilute solution particle dynamics". Thesis, University of Cambridge, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.357751.
Testo completo
25
LI, ZHENLONG. "DYNAMICS OF POLYMER SELF-ASSEMBLY BY COMPUTER SIMULATION". Case Western Reserve University School of Graduate Studies / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=case1296234501.
Testo completo
26
Frignani, Michele <1978>. "Simulation of gas breakdown and plasma dynamics in plasma focus devices". Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2007. http://amsdottorato.unibo.it/414/.
Testo completo
27
Whitehead, L. "Computer simulation of biological membranes and membrane bound proteins". Thesis, University of Southampton, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.297412.
Testo completo
28
Chow, K. "Simulation and analysis of gas freeing of oil tanks". Thesis, Coventry University, 2010. http://curve.coventry.ac.uk/open/items/692c76ab-c812-3ea9-29fe-0fe6cab4e469/1.
Testo completoAbstract (sommario):
This thesis presents an in-depth study of the gas freeing of marine crude oil tanks using numerical simulation, beginning with a general summary of the problem, followed by an outline of the objectives of this work and the main difficulties involved. To outline essential background, a review of numerical methods, fluid flow, and related physical mechanisms has been undertaken, in addition to related ventilation fields, jet and jet impingement, and tanker-borne ventilation, in order to determine the state of the art and draw useful parallels between different ventilative fields, as well as identifying potential areas for model validation. A room-ventilation test case was studied in order to demonstrate the numerical method. It was found that assuming adiabatic walls and ignoring radiation resulted in highly idealised temperature predictions, and that radiation played a large part in enhancing vertical temperature prediction by redistributing thermal energy. For the gas-freeing analysis, the geometric models and solution procedures are introduced before simulation results presented and validated with analytical jet models and impingement penetration parameters. Analysis showed that the internal temperature of the tank was approximately homogeneous, allowing the tank to be considered isothermal. 2D simulations showed that after an initial period of time, the relative concentration distribution reaches steady state with decreasing average concentration as gas-freeing continues. Discussion of the results followed, examining aspects surrounding heat transfer and the choice of turbulence model, analysing the differences in the results between the first and secondmoment closure schemes and justification of assuming isothermal conditions. The variation in concentration was examined, and an analytical expression was derived which approximates the reduction in average gas concentration decay due to gas-freeing. It has been shown that double-hulled construction renders the internal temperature variation to around 10% of the temperature difference between the sea and deck. During the gasfreeing process proper, it was shown that after any stratified layer has been eroded and a stable flow field established, the relative concentration distribution remains constant. Gas freeing times were shown to be heavily dependent on the volume flux (and thus air change rate), and mathematical relations derived in order to provide approximately predict the time to gas free a crude oil tank (COT) given particular initial conditions.
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Whatling, Shaun Gary. "Computer simulation studies of liquid crystals". Thesis, University of Southampton, 1997. https://eprints.soton.ac.uk/421720/.
Testo completo
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Mak, Hing-Yin. "System dynamics and discrete event simulation modelling". Thesis, London School of Economics and Political Science (University of London), 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.263375.
Testo completoAbstract (sommario):
This thesis investigates the relationship between discrete event and system dynamics simulation modelling. Each modelling technique has its own strengths and limitations. The choice of using one particular modelling technique often depends on the preference and the knowledge of the modeller rather than on the nature of the problem. The basis of this research has been to address the problem from a different perspective. This has been to look at the nature of the problem first, and then determine the most appropriate modelling technique to apply. The basic method adopted was to compare, contrast and experiment with these two modelling techniques in order to determine a number of common and unrelated concepts between them. This investigation discovered that a system dynamics flow diagram could be used to represent an activity cycle diagram of a discrete event model. The converted flow diagram can provide a different viewpoint from the discrete event model due to the feedback characteristic of system dynamics. This research went on to develop a set of guidelines to convert an activity cycle diagram into a system dynamics flow diagram. Experimentation with many examples demonstrates that these conversion guidelines provide a consistent and systematic method for obtaining a system dynamics flow diagram. The final stage of this research was to develop a prototype computer system (SMCP) to demonstrate these guidelines. SMCP consists of two modules, the ACD module which allows the user to specify a discrete event model through textual descriptions, and the SD module which allows the user to build a system dynamics model by drawing symbols and using text inputs. In addition, SMCP allows users to convert an ACD to a system dynamics flow diagram quickly and easy, and also demonstrates the concept of data sharing.
31
Hill, David Paul. "The computer simulation of dispersed two-phase flow". Thesis, Imperial College London, 1998. http://hdl.handle.net/10044/1/8733.
Testo completo
32
Duggirala, Ravi Kumar Roy Christopher J. "Computational fluid dynamics simulation of chemically reacting gas flows through microfibrous materials". Auburn, Ala, 2008. http://repo.lib.auburn.edu/EtdRoot/2008/SPRING/Aerospace_Engineering/Dissertation/Duggirala_Ravi_35.pdf.
Testo completo
33
Long, Fei. "Computer simulation techniques of pseudopotential theory and molecular dynamics". Thesis, University of Hull, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343701.
Testo completo
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Arcot, Ramakant P. "Computer simulation of the Bristol compressor suspension system dynamics". Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-09052009-040832/.
Testo completo
35
Jury, Simon Ian. "Computer simulation of complex fluids using dissipative particle dynamics". Thesis, University of Edinburgh, 1999. http://hdl.handle.net/1842/12323.
Testo completoAbstract (sommario):
A parallel code has been developed to implement the Dissipative Particle Dynamics (DPD) simulation algorithm. DPD is a particle based method which simulates the fluid at a mesoscopic scale. Since the DPD interactions are both soft (compared to the potentials used in molecular dynamics) and momentum conserving, DPD offers the possibility of reproducing hydrodynamic behaviour at large length and time scales. Other techniques for hydrodynamic flow simulation are reviewed before the DPD algorithm is presented together with some of the coding issues arising from using a parallel implementation. Equilibrium thermodynamics, as pertaining to phase separation, is presented, together with the scaling arguments used to derive growth laws for domain size. An in depth study of domain size scaling in three dimensional binary fluid phase separation has been completed. For an appropriate choice of parameters, domain growth is shown to enter a regime dominated by capillary and viscous forces. Qualitative analysis of interface maps and velocity fields reveal the Siggia mechanism for domain coarsening in operation. By performing simulations over two orders of magnitude in reduced length and reduced time units, a small yet significant breakdown of scaling is observed in the domain growth rate. Possible explanations for this breakdown are considered. By extending the code, we study a dense solution of an amphiphilic species focusing on the smectic mesophase. Results are presented for the formation of monodomain, bidomain and polydomain lamellar phases. Shearing is performed, using Lees Edwards boundary conditions, the effect of shear on the lamellar phase is examined. It is shown how, for certain concentrations and shear rates, a lamellar structure will tend to fold in upon itself, this is a possible first stage in onion formation.
36
Pinches, Mark Robert Smythe. "Computer simulation of small molecules adsorbed on graphite". Thesis, University of Southampton, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239678.
Testo completo
37
Lukinov, Tymofiy. "Computer simulation of materialsunder extreme conditions". Doctoral thesis, KTH, Kondenserade materiens teori, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-188146.
Testo completoAbstract (sommario):
Extreme conditions allow us to reveal unusual material properties. At the same time an experimental approach is di-cult under such conditions. Capabilities of a theoretical approach based on simplied models are limited. This explainsa wide application of computer simulations at extreme conditions. My thesis is concerned with computer simulations undersuch a conditions. I address such problems as melting, solidsolid phase transitions, shockwave impact on material properties and chemical reactions under extreme conditions. We addressed these problems to facilitate simulations of phase transitions to provide some interpretation of experimental data andexplain enigmatic phenomena in interior of the Earth.QC 20160615
38
Stone, Christopher. "Large-Eddy simulation of combustion dynamics in swirling flows". Diss., Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/13430.
Testo completo
39
Hagy, Matthew Canby. "Dynamical simulation of structured colloidal particles". Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/50328.
Testo completoAbstract (sommario):
In this thesis, computer simulations are used to study the properties of new colloidal systems with structured interactions. These are pair interactions that include both attraction and repulsion. Structured colloids differ from conventional colloids in which the interactions between particles are either strictly attractive or strictly repulsive. It is anticipated that these novel interactions will give rise to new microscopic structure and dynamics and therefore new material properties. Three classes of structured interactions are considered: radially structured interactions with an energetic barrier to pair association, Janus surface patterns with two hemispheres of different surface charge, and striped surface patterns. New models are developed to capture the structured interactions of these novel colloid systems. Dynamical computer simulations of these models are performed to quantify the effects of structured interactions on colloid properties. The results show that structured interactions can lead to unexpected particle ordering and novel dynamics. For Janus and striped particles, the particle order can be captured with simpler isotropic coarse-grained models. This relates the static properties of these new colloids to conventional isotropically attractive colloids (e.g. depletion attracting colloids). In contrast, Janus and striped particles are found to have substantially slower dynamics than isotropically attractive colloids. This is explained by the observation of longer-duration reversible bonds between pairs of structured particles. Dynamical mapping methods are explored to relates the dynamics of these structured colloids to isotropically attractive colloids. These methods could also facilitate future nonequilibrium simulation of structured colloids with computationally efficient coarse-grained models.
40
Han, Jennifer Ching-Wen. "Using system dynamics in business simulation training games". Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/42762.
Testo completoAbstract (sommario):
Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1997.Includes bibliographical references (leaves 57-58).
by Jennifer Ching-Wen Han.
M.Eng.
41
Sourtzinos, Panagiotis. "Vision-based analysis and simulation of pedestrian dynamics". Thesis, Kingston University, 2016. http://eprints.kingston.ac.uk/35839/.
Testo completoAbstract (sommario):
The aim of this thesis is to examine the applicability of computer vision to analyze pedestrian and crowd characteristics, and how pedestrain simulation for shopping environments can be driven from the visual perception of the simulated pedestrians. More specifically, two frameworks for pedestrian speed profile estimation are designed and implemented. The first address the problem of speed estimation for people moving parallel to the image plane on a flat surface, while the other tries to estimate the speed of people walking on stairs moving while their trajectories and being perpendicular on the image plane. Both approaches aim to localise the foot of the pedestrains, and by identifying their steps measure their speed. Except from measuring the speed of pedestrains, a crowd counting system using Convolutional Neural Networks is created by exploiting the background spatial persistence of a whole image in the temporal domain, and furthermore by fusing consecutive temporal counting information in the systme further refines its estimates. Finally a novel memory-free cognitive framework for pedestrian shopping behaviour is presented where the simulated pedestrians use as route choice model their visual perception. Agents moving in an environment and equipped with an activity agenda. use their vision to select not only their root choices but also the shops that they visit.
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Zhang, Junfang. "Computer simulation of nanorheology for inhomogenous fluids". Australasian Digital Thesis Program, 2005. http://adt.lib.swin.edu.au/public/adt-VSWT20050620.095154.
Testo completoAbstract (sommario):
Thesis (PhD) - Swinburne University of Technology, School of Information Technology, Centre for Molecular Simulation - 2005.A thesis submitted in fulfilment of requirements for the degree of Doctor of Philosophy, Centre for Molecular Simulation, School of Information Technology, Swinburne University of Technology - 2005. Typescript. Bibliography: p. 164-170.
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Douglas, I. E. "Development of a generalized computer program for gas turbine performance simulation". Thesis, Cranfield University, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.373986.
Testo completo
44
Board, John Arnold. "Computer simulation of spectral properties of ionic systems". Thesis, University of Oxford, 1986. https://ora.ox.ac.uk/objects/uuid:948decd0-2dc0-42cd-982f-c5d9a3bad1b2.
Testo completoAbstract (sommario):
The technique of Molecular Dynamics (MD) computer simulation is coupled with the interrelated theories of light scattering and atomic polarisability to develop and test models for the Raman scattering from alkali halide systems. The primary interest is in the spectrum and intensity of the scattering from melts, but scattering from crystals is also considered. Two computationally tractable models for the Raman scattering are developed. One, a qualitative model capable of reproducing light scattering lineshapes in Nal, is based on approximations to the quantum-mechanical transition rates for the scattering processes and relies on the shell model interionic potentials from lattice dynamics to give insight into the dynamics of ionic dipole moment fluctuations, from which the scattering behaviour is extracted. The second model is a quantitative one capable of reproducing absolute scattering intensities as well as lineshapes for NaCl melts. This model is based on a detailed parameterisaton of the variation of individual ion polarisabilities with the instantaneous local ionic configuration. The model parameters are extracted from the results of electronic structure calculations on ionic systems performed elsewhere. This model has additionally been applied with some success to NaCl crystal systems. The scattering behaviour of LiF has also been considered, although no experimental comparison is available. The primary failure of the second model is its inability to predict the correct depolarisation ratio for the scattering from NaCl; reasons for this are offered. In developing the models, computer simulation techniques and the light scattering and polarisability theories are reviewed, as are aspects of alkali halide systems, especially interionic potentials suitable for use in simulations. Numerous improvements and extensions to the models are suggested.
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Gemmell, Alastair. "The structure and dynamics of silicate melts from computer simulation". Thesis, University of Oxford, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.433480.
Testo completo
46
Smith, Rhiannon Jane. "A molecular dynamics simulation of the trapping and scattering of Ar on Pt(111)". Thesis, University of Liverpool, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.386787.
Testo completo
47
Warne, Mark Robert. "Computer simulation of molecules at the kaolinite interface". Thesis, University of Bristol, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.322604.
Testo completo
48
Wu, Xiaofeng. "Reduced Deformable Body Simulation with Richer Dynamics". The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1471482167.
Testo completo
49
Schwartz, Russell S. (Russell Steven). "The local rules dynamics model for self-assembly simulation". Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/86426.
Testo completoAbstract (sommario):
Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2000.Includes bibliographical references (p. 173-185).
by Russell S. Schwartz.
Ph.D.
50
Tran, Trung Nam. "Surface discharge dynamics : theory, experiment and simulation". Thesis, University of Southampton, 2010. https://eprints.soton.ac.uk/165509/.
Testo completoAbstract (sommario):
The use of solid insulators in electrical generation, transmission and distribution is widespread. However, the accumulation of charge on the insulator surface has proved to be one of the major factors contributing to system failures. This research work is aimed at studying the dynamics of surface discharge in theory, by simulation and experiment. Different surface charging theories have been reviewed and classiffied according to electric field uniformity. The focus is on basic processes involved in the formation of positive and negative surface discharges. The experimental work utilises the non-destructive quantitative Pockels technique to measure surface charge density distribution. Practical considerations of the Pockels experiment together with image processing techniques are discussed in detail. Using this technique, various factors which influence the surface discharge dynamics have been studied including the effects of the applied voltage waveform, electrode shape and local gaseous environment. Results obtained using positive/negative square wave, ramp and sinusoidal voltages are reported. The impact of using a mushroom electrode instead of a needle electrode is also analysed. In addition, various insulation gases have been experimented namely dry air, N2, CO2 and their mixtures with SF6. Surface discharge measurements have been performed in these gases at various levels of pressure. Surface discharge modelling and simulation studies have also been undertaken. The simulation principles are based on a system of coupled hydrodynamic equations consisting of continuity and Poisson's equations. By solving these equations, the movement and interaction of charged particles and transient electric eld can be simulated and used to verify the discharge theories and experimental results. Due to the asymmetric lamentary nature of positive surface streamers, the development of a positive surface discharge is separated into two phases. The rst phase involves the axial streamer development in the gas gap between the needle electrode and the dielectric surface. This phase is simulated in 2D axial symmetry space dimension by the nite element package COM-SOL. The second phase simulates the streamer propagation in 1D along the dielectric surface by using the eld results from the rst phase. This part of the model is solved by the accurate ux-corrected transport algorithm. The effects of model parameters on the simulation results are discussed and a comparison with experimental data made. Prior to the simulation of a negative surface discharge, a negative corona discharge model in 2D axial symmetry has been analysed (Trichel pulses). The model behaviour is studied with reference to experimental data as model parameters are varied. When the insulators are introduced, the accumulation of surface charge distorts the electric eld leading to the formation of only one discharge current pulse. The simulation charge density distribution is in good agreement with results obtained from the Pockels experiment.