Academic literature on the topic 'RANS (Reynolds-Averaged Navier-Stokes)'
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Journal articles on the topic "RANS (Reynolds-Averaged Navier-Stokes)"
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Güemes, Alejandro, Pablo Fajardo, and Marco Raiola. "Experimental Assessment of RANS Models for Wind Load Estimation over Solar-Panel Arrays." Applied Sciences 11, no. 6 (March 11, 2021): 2496. http://dx.doi.org/10.3390/app11062496.
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This paper reports a comparison between wind-tunnel measurements and numerical simulations to assess the capabilities of Reynolds-Averaged Navier-Stokes models to estimate the wind load over solar-panel arrays. The free airstream impinging on solar-panel arrays creates a complex separated flow at large Reynolds number, which is severely challenging for the current Reynolds-Averaged Navier-Stokes models. The Reynolds-Averaged Navier-Stokes models compared in this article are k-ϵ, Shear-Stress Transport k-ω, transition and Reynolds Shear Model. Particle Image Velocimetry measurements are performed to investigate the mean flow-velocity and turbulent-kinetic-energy fields. Pressure taps are located in the surface of the solar panel model in order to obtain static pressure measurements. All the Reynolds-Averaged Navier-Stokes models predict accurate average velocity fields when compared with the experimental ones. One of the challenging factor is to predict correctly the thickness of the turbulent wake. In this aspect, Reynolds Shear provides the best results, reproducing the wake shrink observed on the 3rd panel in the experiment. On the other hand, some other features, most notably the blockage encountered by the flow below the panels, are not correctly reproduced by any of the models. The pressure distributions over the 1st panel obtained from the different Reynolds-Averaged Navier-Stokes models show good agreement with the pressure measurements. However, for the rest of the panels Reynolds-Averaged Navier-Stokes fidelity is severely challenged. Overall, the Reynolds Shear model provides the best pressure estimation in terms of pressure difference between the front and back sides of the panels.
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Girimaji, Sharath S. "Partially-Averaged Navier-Stokes Model for Turbulence: A Reynolds-Averaged Navier-Stokes to Direct Numerical Simulation Bridging Method." Journal of Applied Mechanics 73, no. 3 (November 8, 2005): 413–21. http://dx.doi.org/10.1115/1.2151207.
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A turbulence bridging method purported for any filter-width or scale resolution—fully averaged to completely resolved—is developed. The method is given the name partially averaged Navier-Stokes (PANS) method. In PANS, the model filter width (extent of partial averaging) is controlled through two parameters: the unresolved-to-total ratios of kinetic energy (fk) and dissipation (fε). The PANS closure model is derived formally from the Reynolds-averaged Navier-Stokes (RANS) model equations by addressing the following question: if RANS represents the closure for fully averaged statistics, what is the corresponding closure for partially averaged statistics? The PANS equations vary smoothly from RANS equations to Navier-Stokes (direct numerical simulation) equations, depending on the values of the filter-width control parameters. Preliminary results are very encouraging.
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Chakraborty, Arnab, and HV Warrior. "Study of turbulent flow past a square cylinder using partially-averaged Navier–Stokes method in OpenFOAM." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 234, no. 14 (March 5, 2020): 2821–32. http://dx.doi.org/10.1177/0954406220910176.
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The present paper reports numerical simulation of turbulent flow over a square cylinder using a novel scale resolving computational fluid dynamics technique named Partially-Averaged Navier–Stokes (PANS), which bridges Reynolds-Averaged Navier–Stokes (RANS) with Direct Numerical Simulation (DNS) in a seamless manner. All stream-wise and wall normal mean velocity components, turbulent stresses behavior have been computed along the flow (streamwise) as well as in transverse (wall normal) direction. The measurement locations are chosen based on the previous studies so that results could be compared. However, the Reynolds number ( Re) of the flow is maintained at 21,400 and K– ω turbulence model is considered for the present case. All the computations are performed in OpenFOAM framework using a finite volume solver. Additionally, turbulent kinetic energy variations are presented over a wide range of measurement planes in order to explain the energy transfer process in highly unsteady turbulent flow field. The fluctuating root mean square velocities in the streamwise as well as in the wall normal direction have been discussed in the present work. It has been found that Partially-Averaged Navier–Stokes (PANS) model is capable of capturing the properties of highly unsteady turbulent flows and gives better results than Reynolds-Averaged Navier–Stokes (RANS). The results obtained using Partially-Averaged Navier–Stokes (PANS) are quite comparable with Large Eddy Simulation (LES) and Direct Numerical Simulation (DNS) data available in literature. The partially-averaged Navier–Stokes results are compared with our simulated Reynolds-Averaged Navier–Stokes (RANS) results, available experimental as well as numerical results in literature and it is found to be good in agreement.
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Netzer, Corinna, Lars Seidel, Frédéric Ravet, and Fabian Mauss. "Assessment of the validity of RANS knock prediction using the resonance theory." International Journal of Engine Research 21, no. 4 (May 8, 2019): 610–21. http://dx.doi.org/10.1177/1468087419846032.
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Following the resonance theory by Bradley and co-workers, engine knock is a consequence of an auto-ignition in the developing detonation regime. Their detonation diagram was developed using direct numerical simulations and was applied in the literature to engine knock assessment using large eddy simulations. In this work, it is analyzed if the detonation diagram can be applied for post-processing and evaluation of predicted auto-ignitions in Reynolds-averaged Navier–Stokes simulations even though the Reynolds-averaged Navier–Stokes approach cannot resolve the fine structures resolved in direct numerical simulations and large eddy simulations that lead to the prediction of a developing detonation. For this purpose, an engine operating point at the knock limit spark advance is simulated using Reynolds-averaged Navier–Stokes and large eddy simulations. The combustion is predicted using the G-equation and the well-stirred reactor model in the unburnt gases based on a detailed gasoline surrogate reaction scheme. All the predicted ignition kernels are evaluated using the resonance theory in a post-processing step. According to the different turbulence models, the predicted pressure rise rates and gradients differ. However, the predicted ignition kernel sizes and imposed gas velocities by the auto-ignition event are similar, which suggests that the auto-ignitions predicted by Reynolds-averaged Navier–Stokes simulations can be given a meaningful interpretation within the detonation diagram.
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Liu, Zhe. "On the Investigation of Flow around the Square Cylinder Based on Different LES Models." Advanced Materials Research 594-597 (November 2012): 2676–79. http://dx.doi.org/10.4028/www.scientific.net/amr.594-597.2676.
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Although the conventional Reynolds-averaged Navier–Stokes (RANS) model has been widely applied in the industrial and engineering field, it is worthwhile to study whether these models are suitable to investigate the flow filed varying with the time. With the development of turbulence models, the unsteady Reynolds-averaged Navier–Stokes (URANS) model, detached eddy simulation (DES) and large eddy simulation (LES) compensate the disadvantage of RANS model. This paper mainly presents the theory of standard LES model, LES dynamic model and wall-adapting local eddy-viscosity (WALE) LES model. And the square cylinder is selected as the research target to study the flow characteristics around it at Reynolds number 13,000. The influence of different LES models on the flow field around the square cylinder is compared.
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Girimaji, Sharath S., Eunhwan Jeong, and Ravi Srinivasan. "Partially Averaged Navier-Stokes Method for Turbulence: Fixed Point Analysis and Comparison With Unsteady Partially Averaged Navier-Stokes." Journal of Applied Mechanics 73, no. 3 (November 8, 2005): 422–29. http://dx.doi.org/10.1115/1.2173677.
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Hybrid/bridging models that combine the advantages of Reynolds averaged Navier Stokes (RANS) method and large-eddy simulations are being increasingly used for simulating turbulent flows with large-scale unsteadiness. The objective is to obtain accurate estimates of important large-scale fluctuations at a reasonable cost. In order to be effective, these bridging methods must posses the correct “energetics”: that is, the right balance between production (P) and dissipation (ε). If the model production-to-dissipation ratio (P∕ε) is inconsistent with turbulence physics at that cutoff, the computations will be unsuccessful. In this paper, we perform fixed-point analyses of two bridging models—partially-averaged Navier Stokes (PANS) and unsteady RANS (URANS)—to examine the behavior of production-to-dissipation ratio. It is shown that the URANS-(P∕ε) ratio is too high rendering it incapable of resolving much of the fluctuations. On the other hand, the PANS-(P∕ε) ratio allows the model to vary smoothly from RANS to DNS depending upon the values of its resolution control parameters.
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Karim, M. M., M. M. Rahman, and M. A. Alim. "Computation of Axisymmetric Turbulent Viscous Flow Around Sphere." Journal of Scientific Research 1, no. 2 (April 22, 2009): 209–19. http://dx.doi.org/10.3329/jsr.v1i2.1286.
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Axisymmetric turbulent viscous flow around sphere is computed using finite volume method based on Reynolds-averaged Navier-Stokes (RANS) equations. Two-dimensional axisymmetric flow solver has been used to analyze flow at Reynolds number of 5Ã106. Spalart-Allmaras (S-A) and shear stress transport (SST) k-Ï turbulence models are used to capture turbulent viscous flow. The numerical results in terms of the skin friction coefficient, pressure coefficient and drag coefficient for different Reynolds numbers have been shown either graphically or in the tabular form. Velocity vectors have been displayed graphically. The computed results show good agreement with published experimental measurements. Keywords: Axisymmetric body of revolution; Sphere; Viscous drag; CFD; Turbulence model; Reynolds-averaged Navier-Stokes (RANS) equations. © 2009 JSR Publications. ISSN: 2070-0237 (Print); 2070-0245 (Online). All rights reserved. DOI: 10.3329/jsr.v1i2.1286
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Wu, Jinlong, Heng Xiao, Rui Sun, and Qiqi Wang. "Reynolds-averaged Navier–Stokes equations with explicit data-driven Reynolds stress closure can be ill-conditioned." Journal of Fluid Mechanics 869 (April 29, 2019): 553–86. http://dx.doi.org/10.1017/jfm.2019.205.
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Reynolds-averaged Navier–Stokes (RANS) simulations with turbulence closure models continue to play important roles in industrial flow simulations. However, the commonly used linear eddy-viscosity models are intrinsically unable to handle flows with non-equilibrium turbulence (e.g. flows with massive separation). Reynolds stress models, on the other hand, are plagued by their lack of robustness. Recent studies in plane channel flows found that even substituting Reynolds stresses with errors below 0.5 % from direct numerical simulation databases into RANS equations leads to velocities with large errors (up to 35 %). While such an observation may have only marginal relevance to traditional Reynolds stress models, it is disturbing for the recently emerging data-driven models that treat the Reynolds stress as an explicit source term in the RANS equations, as it suggests that the RANS equations with such models can be ill-conditioned. So far, a rigorous analysis of the condition of such models is still lacking. As such, in this work we propose a metric based on local condition number function for a priori evaluation of the conditioning of the RANS equations. We further show that the ill-conditioning cannot be explained by the global matrix condition number of the discretized RANS equations. Comprehensive numerical tests are performed on turbulent channel flows at various Reynolds numbers and additionally on two complex flows, i.e. flow over periodic hills, and flow in a square duct. Results suggest that the proposed metric can adequately explain observations in previous studies, i.e. deteriorated model conditioning with increasing Reynolds number and better conditioning of the implicit treatment of the Reynolds stress compared to the explicit treatment. This metric can play critical roles in the future development of data-driven turbulence models by enforcing the conditioning as a requirement on these models.
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Warudkar, Vilas, Pramod Sharma, and Siraj Ahmed. "Evaluation of two wind flow models for wind resource assessment for a site." E3S Web of Conferences 167 (2020): 05001. http://dx.doi.org/10.1051/e3sconf/202016705001.
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There are different numerical wind flow models are existing to simulate atmosphere flows. The conventional approach has been relying on JacksonHunt linear wind flow models, computational fluid dynamics and Reynolds- averaged Navier Stokes models has been explored in research to predict wind resource for a site. The present work aims to analyze the performance of two wind flow models to predict the variation of wind speed. The two are 1) WAsP (linear JacksonHunt model) and 2) CFD/RANS models. The wind flow numerical models are compared with high-quality measurements from single meteorological mast. It has been found that the root meant square error for the WAsP model is 23% greater than the Reynolds- averaged Navier Stokes model.
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Wu, Junjie, Jiahua Li, Xiang Qiu, Xilin Xie, and Yulu Liu. "Machine learning based Reynolds averaged simulation of backward-facing step flows at different Reynolds numbers." Modern Physics Letters B 35, no. 25 (August 16, 2021): 2150430. http://dx.doi.org/10.1142/s0217984921504303.
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To address the closure problem of Reynolds-averaged Navier–Stokes in numerical simulations of turbulence, the method of solving Reynolds-averaged Navier–Stokes equations based on artificial neural network is introduced in this paper. We establish the nonlinear mapping relationship between the average flow field and the steady-state eddy viscosity field. The machine learning (ML) surrogate model for the shear stress transport turbulence model is constructed. The solution process of replacing the original turbulence model equations with the predicted field variables is realized by coupling the ML algorithm with the CFD solver. The classical backward facing step problem is selected in our study to verify the simulation accuracy of the surrogate model. The comparative analysis is carried out on the six backward facing step flows simulations at different Reynolds numbers. The results of simulations show that the testing flows with the Reynolds numbers closest training datasets Reynolds numbers can obtain the best simulation accuracy. Then for the Reynolds number that is lower than the training datasets, the simulation accuracy will decrease as the Reynolds number decreases. On the contrary, the simulation accuracy of the test flow will increase as the Reynolds number increases. These results indicate the feasibility of the ML surrogate model to simulate at higher Reynolds number. It shows the great potential of applying ML algorithms to Reynolds-averaged Navier–Stokes simulation (RANS) turbulence model and also provides a new idea for industrial simulations of turbulent flows.
Dissertations / Theses on the topic "RANS (Reynolds-Averaged Navier-Stokes)"
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Frazza, Loïc. "3D anisotropic mesh adaptation for Reynolds Averaged Navier-Stokes simulations." Thesis, Sorbonne université, 2018. http://www.theses.fr/2018SORUS423.
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Nous montrons dans cette thèse la capacité des schémas numériques modernes à simuler des écoulements turbulents sur des maillages totalement non-structurés générés automatiquement à l’aide de méthodes adaptatives. Nous détaillons le développement de différentes versions du modèle de Spalart-Allmaras ainsi que les choix numériques garantissant une robustesse suffisante du solver pour ne pas nécessiter de couche limite structurée. Nous introduisons en suite l’analyse d’erreur nécessaire pour proposer different estimateurs d’erreur à la base de l’optimisation de maillage. Cette méthodologie est testée sur différents cas tests d’aérodynamique externe et de turbomachines et comparée aux méthodes traditionnelles de géneration de maillage. Nous montrons ainsi la capacité des méthodes d’adaptation de maillage à générer automatiquement des maillages adaptés optimaux pour les simulations RANS autour de géométries réalistes et complexesThe fast and reliable simulation of turbulent flow using Reynolds Averaged Navier Stokes (RANS) models is a major financial issue for many industries. With the increasing complexity of geometries and simulated flows, as well as requirements in terms of fidelity, the generation of appropriate meshes has become a key link in the chain of computation. We show in this thesis the ability of modern numerical schemes to simulate turbulent flows on fully unstructured meshes generated automatically using mesh adaptation methods. We present the implementation of different versions of the Spalart-Allmaras model as well as the numerical choices guaranteeing a sufficient robustness of the solver in order to not require a structured boundary layer. We then introduce the error analysis necessary to propose different error estimators for mesh optimization. This methodology is tested on various external aerodynamic and turbomachinery test cases and compared to traditional mesh generation methods. We show the ability of mesh adaptation methods to automatically generate optimal mesh sizes for RANS simulations on realistic and complex geometries
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Shin, Sangmook. "Reynolds-Averaged Navier-Stokes Computation of Tip Clearance Flow in a Compressor Cascade Using an Unstructured Grid." Diss., Virginia Tech, 2001. http://hdl.handle.net/10919/28947.
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A three-dimensional unstructured incompressible RANS code has been developed using artificial compressibility and Spalart-Allmaras eddy viscosity model. A node-based finite volume method is used in which all flow variables are defined at the vertices of tetrahedrons in an unstructured grid. The inviscid fluxes are computed by using the Roe's flux difference splitting method, and higher order accuracy is attained by data reconstruction based on Taylor series expansion. Gauss theorem is used to formulate necessary gradients. For time integration, an implicit scheme based on linearized Euler backward method is used.
A tetrahedral unstructured grid generation code has been also developed and applied to the tip clearance flow in a highly staggered cascade. Surface grids are first generated in the flow passage and blade tip by using several triangulation methods including Delaunay triangulation, advancing front method and advancing layer method. Then the whole computational domain including tip gap region is filled with prisms using the surface grids. Each prism is divided into three tetrahedrons. To accomplish this division in a consistent manner, connectivity pattern is assigned to each triangle in the surface grids. A new algorithm is devised to assign the connectivity pattern without reference to the particular method of triangulation. This technique offers great flexibility in surface grid generation.
The code has been validated by comparisons with available computational and experimental results for several test cases: invisicd flow around NACA section, laminar and turbulent flow over a flat plate, turbulent flow through double-circular arc cascade and laminar flow through a square duct with 90° bend. For the laminar flat plate case, the velocity profile and skin friction coefficient are in excellent agreement with Blasius solution. For the turbulent flat plate case, velocity profiles are in full agreement with the law of the wall up to Reynolds number of 1.0E8, however, the skin friction coefficient is under-predicted by about 10% in comparison with empirical formula. Blade loading for the two-dimensional circular arc cascade is also compared with experiments. The results obtained with the experimental inflow angle (51.5° ) show some discrepancies at the trailing edge and severely under-predict the suction peak at the leading edge. These discrepancies are completely remedied if the inflow angle is increased to 53.5° . The code is also capable of predicting the secondary flow in the square duct with 90° bend, and the velocity profiles are in good agreement with measurements and published Navier-Stokes computations.
Finally the code is applied to a linear cascade that has GE rotor B section with tip clearance and a high stagger angle of 56.9° . The overall structure of the tip clearance flow is well predicted. Loss of loading due to tip leakage flow and reloading due to tip leakage vortex are presented. On the end wall, separation line of the tip leakage vortex and reattachment line of passage vortex are identified. The location of the tip leakage vortex in the passage agrees very well with oil flow visualization. Separation bubble on the blade tip is also predicted. Mean streamwise velocity contours and cross sectional velocity vectors are compared with experimental results in the near wake, and good agreements are observed. It is concluded that Spalart-Allmaras turbulence model is adequate for this type of flow field except at locations where the tip leakage vortex of one blade interacts with the wake of a following blade. This situation may prevail for blades with longer span and/or in the far wake. Prediction of such an interaction presents a challenge to RANS computations.
The effects of blade span on the flow structure have been also investigated. Two cascades with blades of aspect ratios of 0.5 and 1.0 are considered. By comparing pressure distributions on the blade, it is shown that the aspect ratio has strong effects on loading distribution on the blade although the tip gap height is very small (0.016 chord). Grid convergence study has been carried out with three different grids for pressure distributions and limiting streamlines on the end wall.Ph. D.
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Li, Zhiyong. "Data-Driven Adaptive Reynolds-Averaged Navier-Stokes k - ω Models for Turbulent Flow-Field Simulations." UKnowledge, 2017. http://uknowledge.uky.edu/me_etds/93.
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The data-driven adaptive algorithms are explored as a means of increasing the accuracy of Reynolds-averaged turbulence models. This dissertation presents two new data-driven adaptive computational models for simulating turbulent flow, where partial-but-incomplete measurement data is available. These models automatically adjust (i.e., adapts) the closure coefficients of the Reynolds-averaged Navier-Stokes (RANS) k-ω turbulence equations to improve agreement between the simulated flow and a set of prescribed measurement data.
The first approach is the data-driven adaptive RANS k-ω (D-DARK) model. It is validated with three canonical flow geometries: pipe flow, the backward-facing step, and flow around an airfoil. For all 3 test cases, the D-DARK model improves agreement with experimental data in comparison to the results from a non-adaptive RANS k-ω model that uses standard values of the closure coefficients.
The second approach is the Retrospective Cost Adaptation (RCA) k-ω model. The key enabling technology is that of retrospective cost adaptation, which was developed for real-time adaptive control technology, but is used in this work for data-driven model adaptation. The algorithm conducts an optimization, which seeks to minimize the surrogate performance, and by extension the real flow-field error. The advantage of the RCA approach over the D-DARK approach is that it is capable of adapting to unsteady measurements. The RCA-RANS k-ω model is verified with a statistically steady test case (pipe flow) as well as two unsteady test cases: vortex shedding from a surface-mounted cube and flow around a square cylinder. The RCA-RANS k-ω model effectively adapts to both averaged steady and unsteady measurement data.
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Somero, John Ryan. "Computational Simulations of a Non-body of Revolution Ellipsoidal Model Utilizing RANS." Thesis, Virginia Tech, 2010. http://hdl.handle.net/10919/36135.
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The ability of Reynolds Averaged Navier Stokes (RANS) models to predict the characteristics of a non-Body of Revolution (non-BOR) Ellipsoidal model is studied to establish the feasibility of utilizing RANS as a non-BOR concept design tool. Data unable to be obtained experimentally, such as streamwise and spanwise pressure gradients and yaw turn boundary layer characteristics, are also established. A range of conditions are studied including ahead, pitched up, steady 10 and 15 degree yaw turns, and unsteady 10 and 15 degree yaw turns. Simulation results show good agreement for ahead and pitched forces and moments. Straight ahead skin friction values also showed good agreement, providing even improved agreement over an LES model which utilized wall functions. Yaw turn conditions also showed good agreement for roll angles up to 10 degrees. Steady maneuvering forces and moments showed good agreement up to 10 degrees roll and separation calculations also showed good agreement up to 10 degrees roll. Unsteady maneuvering characteristics showed mixed results, with the normal force and pitching moment trends generally agreeing with experimental data, whereas the unsteady rolling moment did not tend to follow experimental trends. Two primary conditions, the change in curvature between the mid-body and elliptical ends and the accuracy of modeling of 3D flows with RANS, are discussed as sources of discrepancies between the experimental data and steady simulations greater than 10 degrees roll and unsteady rolling simulations.Master of Science
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Srinivasa, Murthy P. "Low Reynolds Number Airfoil Aerodynamics." Thesis, Indian Institute of Science, 2000. http://hdl.handle.net/2005/229.
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In this thesis we describe the development of Reynolds- averaged Navier Stokes code for the flow past two- dimensional configuration. Particularly, emphasis has been laid on the study of low Reynolds number airfoil aerodynamics.
The thesis consists of five chapters covering the back ground history, problem formulation, method of solution and discussion of the results and conclusion.
Chapter I deals with a detailed background history of low Reynolds number aerodynamics, problem associated with it, state of the art, its importance in practical applications in aircraft industries.
Chapter II describes the mathematical model of the flow physics and various levels of approximations. Also it gives an account of complexity of the equations at low Reynolds number regarding flow separation, transition and reattachment.
Chapter III describes method of solution, numerical algorithm developed, description of various upwind schemes, grid system, finite volume discrieti-zation of the governing equations described in Chapter II.
Chapter IV describes the application of the newly developed Navier Stokes code for the test cases from GAMM Workshop proceedings. Also it describes validation of the code for Euler solutions, Blasius solution for the flow past flat plate and compressible Navier Stokes solution for the flow past NACA 0012 Airfoil at low Reynolds number.
Chapter V describes the application of the Navier Stokes code for the more test cases of current practical interest . In this chapter laminar separation bubble characteristics are investigated in detail regarding formation, growth and shedding in an unsteady environment.
Finally the conclusion is drawn regarding the robustness of the newly developed code in predicting the airfoil aerodynamic characteristics at low Reynolds number both in steady and unsteady environment.
Lastly, suggestion for future work has been highlighted.
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Henning, H. L. "A numerical investigation into the heave, sway and roll motions of typical ship like hull sections using RANS numerical methods." Thesis, Stellenbosch : Stellenbosch University, 2011. http://hdl.handle.net/10019.1/18033.
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Thesis (MScEng)--Stellenbosch University, 2011.ENGLISH ABSTRACT: The hydrodynamic characteristics of three typical ship-like hull sections, in different motions, are numerically investigated using FLUENT, 2009. These simple shapes, namely a v-bottom (triangle) hull, a at-bottom (square) hull and a round-bottom (semi-circle) hull, are investigated in uncoupled heave, sway and roll. The problem is described in two dimensions. A combination of numerical methods and models, found in literature, are used to conduct this investigation. Hull characterisation is achieved through the use of hull mass and damping coe cients. These numerically determined coe cients are compared to experimental work conducted by Vugts (1968). A good correlation between the numerical and experimental results exists for the heave and sway cases. By normalising the coe cients, different hulls are comparable to one another. The numerical models used are validated and veri ed. Roll motion remains largely unsolved for very large angles of roll (in excess of 11°). Different uid ow phenomena occurring around the hull sections have varying degrees of in uence on the motions of a hull. It is found that not one of the turbulence models investigated can be employed to globally solve each type of hull-motion case. Also, forced oscillations in computational simulations require considerably more computational time than free-decay oscillating hull simulations.
AFRIKAANSE OPSOMMING: Die hidrodinamiese karakteristieke van verskillende skeepsrompvorms, in verskeie bewegingswieë, is numeries ondersoek met behulp van FLUENT, 2009. Drie eenvoudige vorms ('n v-bodem (driehoek), plat-bodem (reghoek) en rondebodem (semi-sirkel) romp) is onderskeidelik ondersoek in opwieg, dwarswieg en rol. Die probleem is twee-dimensioneel. Daar is gebruik gemaak van 'n kombinasie van numeriese metodes en modelle, uit die literatuur, om die ondersoek uit te voer. Die rompe is gekarakteriseer met behulp van massa- en dempingskoëffi siënte. Hierdie numeries bepaalde koë ffisiënte is vergelyk met die eksperimentele werk van Vugts (1968). Daar bestaan 'n goeie korrelasie tussen die numeriese en eksperimentele resultate vir die opwieg en dwarswieg gevalle. Die koë ffisiënte is genormaliseer om die verskeie rompvorms te vergelyk. Die numeriese modelle is geverifi eer en valideer. Rolbewegings is onopgelos vir groot rolhoeke (groter as 11°). Die mate waartoe die romp se beweging beïnvloed word deur die verskillende vloei verskynsels wat om die rompe ontstaan, verskil. Daar is bevind dat geen van die turbulensie modelle gebruik kan word om alle skeepsbeweging-gevalle op te los nie. Gedwonge-ossilasie numeriese simulasies benodig meer berekeningstyd as vrye-verval ossilasie gevalle.
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Divaret, Lise. "U-RANS Simulation of fluid forces exerted upon an oscillating tube array." Thesis, KTH, Farkost och flyg, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-32747.
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The aim of this master thesis is to characterize the fluid forces applied to a fuel assembly inthe core of a nuclear power plant in case of seism. The forces are studied with a simplifiedtwo-dimensional model constituted of an array of 3 by 3 infinite cylinders oscillating in aclosed box. The axial flow of water, which convects the heat in the core of a nuclear powerplant, is also taken into account. The velocity of the axial flow reaches 4m/s in the middle ofthe assembly and modifies the forces features when the cylinders move laterally.The seism is modeled as a lateral displacement with high amplitude (several cylinderdiameters) and low frequencies (below 20 Hz). In order to study the effects of the amplitudeand of the frequency of the displacement, the displacement taken is a sine function withboth controlled amplitude and frequency. Four degrees of freedom of the system will bestudied: the amplitude of the displacement, its frequency, the axial velocity amplitude andthe confinement (due to the closed box).The fluid forces exerted on the cylinders can be seen as a combination of three terms: anadded mass, related to the acceleration of cylinders, a drift force, related to the damping ofthe fluid and a force due to the interaction of the cylinder with residual vortices. The firsttwo components will be characterized through the Morison expansion, and their evolutionwith the variation of the degree of freedom of the system will be quantified. The effect ofthe interaction with the residual vortices will be observed in the plots of the forces vs. timebut also in the velocity and vorticity map of the fluid.The fluid forces are calculated with the CFD code Code_Saturne, which uses a second orderaccurate finite volume method. Unsteady Reynolds Averaged Navier Stokes simulations arerealized with a k-epsilon turbulence model. The Arbitrary Lagrange Euler model is used todescribe the structure displacement. The domain is meshed with hexahedra with thesoftware gmsh [1] and the flow is visualized with Paraview [2]. The modeling techniquesused for the simulations are described in the first part of this master thesis.
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Thiam, Mor Tallla. "Développement et validation expérimentale d'une approche numérique pour la simulation de l'aérodynamique et de la thermique d'un véhicule à trois roues." Thèse, Université de Sherbrooke, 2016. http://hdl.handle.net/11143/9724.
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La compréhension de l'aérothermique d'un véhicule durant sa phase de développement est une question essentielle afin d'assurer, d'une part, un bon refroidissement et une bonne efficacité de ses composants et d'autre part de réduire la force de traînée et évidement le rejet des gaz à effet de serre ou la consommation d'essence. Cette thèse porte sur la simulation numérique et la validation expérimentale de l'aérothermique d'un véhicule à trois roues dont deux, en avant et une roue motrice en arrière. La simulation numérique est basée sur la résolution des équations de conservation de la masse, de la quantité de mouvement et de l'énergie en utilisant l'approche RANS (Reynolds-Averaged Navier-Stokes). Le rayonnement thermique est modélisé grâce à la méthode S2S (Surface to Surface) qui suppose que le milieu séparant les deux surfaces rayonnantes, ici de l'air, ne participe pas au processus du rayonnement. Les radiateurs sont considérés comme des milieux poreux orthotropes où la perte de pression est calculée en fonction de leurs propriétés inertielle et visqueuse; leur dissipation thermique est modélisée par la méthode Dual flow. Une première validation de l'aérodynamique est faite grâce à des essais en soufflerie. Ensuite, une deuxième validation de la thermique est faite grâce à des essais routiers. Un deuxième objectif de la thèse est consacré à la simulation numérique de l'aérodynamique en régime transitoire du véhicule. La simulation est faite à l'aide de l'approche Detached eddy simulation (DES). Une validation expérimentale est faite à partir d'étude en soufflerie grâce à des mesures locales de vitesse à l'aide de sondes cobra.
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Norman, Adam Edward. "A Fundamental Study of Advance Ratio, Solidity, Turbine Radius, and Blade Profile on the Performance Characteristics of Vertical Axis Turbines (VATs)." Thesis, Virginia Tech, 2016. http://hdl.handle.net/10919/81836.
Full textAbstract:
In this dissertation, various VAT parameters are investigated to determine the effect of the overall efficiency of the turbine at a high Reynolds number. To increase the efficiency of the vertical axis turbines, 2D CFD simulations are completed in an effort to better understand the physics behind the operation of these turbines. Specifically, the effect of advance ratio, solidity, and wake interactions were investigated. Simulations were completed in OpenFOAM using the k-ω SST turbulence model at a nominal Reynolds number of 500,000 using a NACA 0015 airfoil. To simulate the motion of the turbine, Arbitrary Mesh Interfacing (AMI) was used. For all of the parameters tested, it was found that the geometric effective angle of attack seen by the turbine blades had a significant impact on the power extracted from the flow. The range of effective angles of attack was found to decrease as the advance ratio increased. In spite of this, a severe loss in the power coefficient occurred at an advance ratio of 2.5 during which the blade experienced dynamic stall. This effect was also seen when the number of turbine blades was changed to four, at a solidity of 1.08. This negative impact on performance was found to be due to the increase in the drag component of the tangential force when dynamic stall occurs. Results indicate that wake interactions between subsequent blades have a large impact on performance especially when the wake interaction alters the flow direction sufficiently to create conditions for dynamic stall.
To improve the performance of the VAT in the presence of dynamic stall, calculations were completed of a static twisted blade profile using GenIDLEST and OpenFOAM. There was found to be no improvement in the lift coefficient when comparing the twisted blade profile with a 2D blade at the same median angle of attack as the twisted blade. To further see the effects of the twisted blade, an effective VAT pitching motion was given to the blade and again compared to a 2D blade with the same motion. In this case there was significant improvement seen in the performance of the twisted blade.Master of Science
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Süer, Assiye. "LES Simulation of Hot-wire Anemometers." Thesis, Luleå tekniska universitet, Institutionen för system- och rymdteknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-62264.
Full textAbstract:
Hot wire anemometers have been used in several wind velocity sensors deployed in Mars. They are based in keeping the temperature of a surface at a constant value, above the ambient. This is done by means of a heater controlled with an electronic system. The cooling rate of each point at the sensor surface can be used to calculate the wind velocity and direction. However, due to turbulent fluctuations, the cooling rate is not constant even in the case of constant velocity. Moreover, RANS simulations cannot estimate such fluctuations as they only provide an estimation of the averaged flow field. The goal of this work has been to estimate such fluctuations and the e↵ect they might have on the sensor readings. To do so, the turbulent cooling rate (Nusselt number) of a sensor with a generic shape, under the typical conditions to be find in Mars, has been simulated using high performance LES (Large Eddy Simulation) simulations and compared with RANS and URANS simulations.
Book chapters on the topic "RANS (Reynolds-Averaged Navier-Stokes)"
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Schumann, Jan-Erik, Markus Fertig, Volker Hannemann, Thino Eggers, and Klaus Hannemann. "Numerical Investigation of Space Launch Vehicle Base Flows with Hot Plumes." In Notes on Numerical Fluid Mechanics and Multidisciplinary Design, 179–91. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-53847-7_11.
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Abstract The flow field around generic space launch vehicles with hot exhaust plumes is investigated numerically. Reynolds-Averaged Navier-Stokes (RANS) simulations are thermally coupled to a structure solver to allow determination of heat fluxes into and temperatures in the model structure. The obtained wall temperatures are used to accurately investigate the mechanical and thermal loads using Improved Delayed Detached Eddy Simulations (IDDES) as well as RANS. The investigated configurations feature cases both with cold air and hot hydrogen/ water vapour plumes as well as cold and hot wall temperatures. It is found that the presence of a hot plume increases the size of the recirculation region and changes the pressure distribution on the nozzle structure and thus the loads experienced by the vehicle. The same effect is observed when increasing the wall temperatures. Both RANS and IDDES approaches predict the qualitative changes between the configurations, but the reattachment location predicted by IDDES is up to 7% further upstream than that predicted by RANS. Additionally, the heat flux distribution along the nozzle and base surface is analysed and shows significant discrepancies between RANS and IDDES, especially on the nozzle surface and in the base corner.
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Caillet, Hélène, Alain Bastide, and Laetitia Adelard. "CFD Simulations in Mechanically Stirred Tank and Flow Field Analysis: Application to the Wastewater (Sugarcane Vinasse) Anaerobic Digestion." In Wastewater Treatment [Working Title]. IntechOpen, 2020. http://dx.doi.org/10.5772/intechopen.93926.
Full textAbstract:
Anaerobic digestion is a widely used process for waste treatment and energy production. This natural process takes place in a controlled environment, anaerobic digesters. Mixing is one of the main operating parameters. The understanding of the flows during the agitation of the medium is crucial for the optimization of the process yield. In fact, the mass and heat transfers are enhanced by the agitation. However, the complex biochemical reactions can be inhibited with overly vigorous agitation. A detailed and in-depth understanding of the phenomena occurring during agitation requires modeling studies. In this chapter, we propose a general approach, based on computational fluid mechanics (CFD), to analyze the mechanical mixing of an anaerobic reactor. We apply this work to the anaerobic digestion of the sugarcane vinasse, which is a liquid waste generated during the production of alcohol. The single-phase Reynolds-averaged Navier-Stokes (RANS) simulations of mechanical agitation of Newtonian fluids for different rotational speeds are presented. The equations system is closed with the standard k-epsilon turbulence model. The flow field is analyzed with the velocity profiles, the Q and Lambda2 fields, the pressure and the vorticity.
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Alkan, Ahmet Dursun, Onur Usta, Alpay Acar, and Elis Atasayan. "Investigation of Environmental Effects of High Speed Boats." In Progress in Marine Science and Technology. IOS Press, 2020. http://dx.doi.org/10.3233/pmst200021.
Full textAbstract:
Luxury high-speed boats are increasingly being used for entertainment purposes. However, not only humans, but also animals are negatively affected by high-speed boats, and time is running out fast for people to do something about it. This study presents a review of current negative effects of high-speed boats to the environment. In this study, the flow around a benchmark planing Fridsma boat is simulated by CFD and resistance values for different non-dimensional Froude number (Fn) conditions are validated from the experimental results obtained from the literature. Using the same CFD methodology, a catamaran model in which the towing tank test results are available, is simulated for different Fn conditions and resistance values are predicted. In the CFD analysis, unsteady flow around the Fridsma hull model and catamaran model is simulated using overset meshing technique and turbulence is modeled by Reynolds Averaged Navier Stokes (RANS) with SST (Menter) k-omega turbulence model. Resistance values are compared with the experimental data and required propulsion powers are estimated for different Fn conditions. Then, total resistance of the catamaran for full-scale vessel is calculated using an extrapolation method and required propulsion power predictions are conducted. Noise prediction, corresponding to the required propulsion power are presented. In particular, the change of noise level and harmful gases released into the environment, when the speed of the vessel increases are examined and discussed. Consequently, it is believed that this study would lay an important foundation for the widespread investigation for the negative effects of the high-speed boats in the future.
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"Reynolds Averaged Navier-Stokes Equations (RANSE)." In Fundamentals of Ship Hydrodynamics, 82–93. Chichester, UK: John Wiley & Sons, Ltd, 2019. http://dx.doi.org/10.1002/9781119191575.ch8.
Full textConference papers on the topic "RANS (Reynolds-Averaged Navier-Stokes)"
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Pereira, Filipe S., Guilherme Vaz, Luís Eça, and Sébastien Lemaire. "On the Numerical Prediction of Transitional Flows With Reynolds-Averaged Navier-Stokes and Scale-Resolving Simulation Models." In ASME 2016 35th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/omae2016-54414.
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The present work investigates the transitional flow around a smooth circular cylinder at Reynolds number Re = 140,000. The flow is resolved using the viscous-flow solver ReFRESCO, and distinct mathematical models are applied to assess their ability to handle transitional flows. The selected mathematical models are the Reynolds-Averaged Navier-Stokes equations (RANS), Scale-Adaptive Simulation (SAS), Delayed Detached-Eddy Simulation (DDES), eXtra Large-Eddy Simulation (XLES) and Partially-Averaged Navier-Stokes (PANS) equations. The RANS equations are supplemented with the k–ω Shear-Stress Transport (SST) with and without the Local Correlation Transition Model (LCTM). The numerical simulations are carried out using structured grids ranging from 9.32 × 104 to 2.24 × 107 cells, and a dimensionless time-step of 1.50 × 10−3. As expected, the outcome demonstrates that transition from laminar to turbulent regime is incorrectly predicted by the k–ω SST model. Transition occurs upstream of the flow separation, which is typical of the supercritical regime and so the flow physics is incorrectly modelled. Naturally, all Scale-Resolving Simulation (SRS) models that rely on RANS to solve the boundary-layer, called hybrid models, will exhibit a similar trend. On the other hand, mathematical models capable to resolve part of the turbulence field in the boundary layer (PANS) lead to a better agreement with the experimental data. Furthermore, the k–ω SST LCTM is also able to improve the modelling accuracy when compared to the k–ω SST. Therefore, it might be a valuable engineering tool if its computational demands are considered (in the RANS context). Therefore, the results confirm that the choice of the most appropriate mathematical model for the simulation of turbulent flows is not straightforward and it may depend on the details of the flow physics.
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Petrova, N., V. Sabelnikov, and N. Bertier. "Numerical simulation of a backward-facing step combustor using reynolds-averaged navier–stokes / extended partially stirred reactor model." In Progress in Propulsion Physics – Volume 11. Les Ulis, France: EDP Sciences, 2019. http://dx.doi.org/10.1051/eucass/201911625.
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The authors adapt recently developed a large eddy simulation / extended partially stirred reactor (LES/EPaSR) model by Sabelnikov and Fureby for simulation of turbulent combustion to Reynolds-averaged Navier–Stokes (RANS) equations. The proposed RANS/EPaSR model is validated against experimental database created at ONERA for an air–methane premixed flame stabilized by a backward-facing step combustor. The RANS/EPaSR model is compared also with the following RANSbased combustion models: (i) quasi-laminar model with reduced chemical mechanism (QL RCM); (ii) premixed flamelet tabulated chemistry (PFTC) without taking into account the turbulence–chemistry interaction (TCI); and (iii) a PFTC with a presumed β probability density function (PDF) for a progress combustion variable.
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Routson, Daniel, James Ferguson, John Crepeau, Donald McEligot, and Ralph Budwig. "Reynolds Averaged Navier Stokes Models Compared to Direct Numerical Simulations in an Adverse Pressure Gradient Boundary Layer Over a Flat Plate." In ASME 2013 Fluids Engineering Division Summer Meeting. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/fedsm2013-16554.
Full textAbstract:
In Reynolds-Averaged Navier Stokes (RANS) models simplifying assumptions breakdown in near wall regions. Wall functions/treatments become inaccurate and the homogeneity and isotropy models may not hold. To see the effect that these assumptions have on the validity of boundary layer results in a commercially available RANS code, key boundary layer parameters are compared from laminar, transitional, and fully turbulent RANS results to an existing direct numerical simulation (DNS) simulation for flow over a flat plate with an adverse pressure gradient (APG). Parameters compared include velocity profiles in the free stream, boundary layer thicknesses, skin friction coefficient and the pressure gradient parameter. Results show comparable momentum thickness and pressure gradient parameters between the transition RANS model and the DNS simulation. Differences in the onset of transition between the RANS transition model and DNS are compared as well. These simulations help evaluate the models used in the RANS code. Of most interest is the transition model, a transition shear-stress transport (SST) k–omega model. The RANS code is being used in conjunction with an APG boundary layer experiment being undertaken at the Idaho National Laboratory (INL).
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Girimaji, Sharath S., Ravi Srinivasan, and Euhwan Jeong. "PANS Turbulence Model for Seamless Transition Between RANS and LES: Fixed-Point Analysis and Preliminary Results." In ASME/JSME 2003 4th Joint Fluids Summer Engineering Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/fedsm2003-45336.
Full textAbstract:
Partially-averaged Navier-Stokes (PANS) approach has been recently developed as a possible bridging model between Reynolds-averaged Navier-Stokes (RANS) method and large-eddy simulations (LES). The resolution control parameters in PANS are the fractions of unresolved kinetic energy (fk) and unresolved dissipation (fε). We investigate the fixed-point behavior of PANS and present some preliminary results obtained using this model. By comparing the fixed-point behavior of PANS and URANS (unsteady Reynolds-averaged Navier-Stokes) methods, the possible advantage of the former over the latter is explained. Initial results from two-dimensional simulations of flow past square results are also presented.
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Schobeiri, M. T. "Intermittency Based Unsteady Boundary Layer Transition Modeling: Implementation Into Navier-Stokes Equations." In ASME Turbo Expo 2005: Power for Land, Sea, and Air. ASMEDC, 2005. http://dx.doi.org/10.1115/gt2005-68375.
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This paper presents recent advances in boundary layer research that deal with an intermittency based unsteady boundary layer transition model and its implementation into the Reynolds averaged Navier-Stokes equations (RANS). RANS equations are conditioned to include the ensemble averaged unsteady intermittency function. The unsteady boundary layer transition model is based on a universal unsteady intermittency function developed earlier. It accounts for the effects of periodic unsteady wake flow on the boundary layer transition. The transition model is the result of an inductive approach analyzing the unsteady data obtained by experiments on a curved plate at zero-streamwise pressure gradient under periodic unsteady wake flow. To validate this model, systematic experimental investigations were conducted on the suction and pressure surfaces of turbine blades that were integrated into a turbine cascade test facility, which was designed for unsteady boundary layer investigations. This model is implemented into the above mentioned conditioned RANS-equations and calculation results are presented.
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Le´onard, Thomas, Florent Duchaine, Nicolas Gourdain, and Laurent Y. M. Gicquel. "Steady/Unsteady Reynolds Averaged Navier-Stokes and Large Eddy Simulations of a Turbine Blade at High Subsonic Outlet Mach Number." In ASME Turbo Expo 2010: Power for Land, Sea, and Air. ASMEDC, 2010. http://dx.doi.org/10.1115/gt2010-22469.
Full textAbstract:
Reynolds Averaged Navier-Stokes (RANS), Unsteady RANS (URANS) and Large Eddy Simulation (LES) numerical approaches are clear candidates for the understanding of turbine blade flows. For such blades, the flow unsteady nature appears critical in certain situations and URANS or LES should provide more physical understanding as illustrated here for a laboratory high outlet subsonic Mach blade specifically designed to ease numerical validation. Although RANS offers good estimates of the mean isentropic Mach number and boundary layer thickness, LES and URANS are the only approaches that reproduce the trailing edge flow. URANS predicts the mean trailing edge wake but only LES offers a detailed view of the flow. Indeed LES’s identify flow phenomena in agreement with the experiment, with sound waves emitted from the trailing edge separation point that propagate upstream and interact with the lower blade suction side.
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Sabetghadam, Fereydoun. "Generalization of the RANS Equations Using Mean Modal Decomposition of the Navier Stokes Equations." In ASME 7th Biennial Conference on Engineering Systems Design and Analysis. ASMEDC, 2004. http://dx.doi.org/10.1115/esda2004-58395.
Full textAbstract:
A generalization in the Reynolds decomposition and averaging are proposed in this paper. The method is directly applied to the Navier Stokes (N-S) equations to construction of a generalized Reynolds Averaged Navier Stokes (RANS) equations. The formulation which is presented for the fields realized in a suitable ensemble, is based on a two part decomposition. One part is an approximate unique representation of the field and when reconstruction of the field, will repeat in all ensemble elements. The other part represents deviation of the real field from the approximate part and therefore is different in any mode and each ensemble element. The decomposition is applied in both spatial and temporal fashions. In the temporal decomposition, a system of Partial Differential Equations (PDEs) is obtained that is nonclosed, coupled and second order in space and its zeroth mode is the classical Reynolds averaged values of the field. In the spatial decomposition whereas, a first order system of nonclosed PDEs is obtained which could be seen as an alternative version of the Proper Orthogonal Decomposition (POD) or the Coherent Vortex Simulation (CVS) methods. In both fashions however, there are some terms that must be modeled just like as the classical closure problem in the RANS method. The method is applied on a one dimensional mixed random-nonrandom field and successfully extracted the coherent part of the field.
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Yang, Jiandao, Taowen Chen, Jun Li, and Zhenping Feng. "Aerodynamic Optimization Design of Exhaust Hood Diffuser for Steam Turbine With Three-Dimensional Reynolds-Averaged Navier-Stokes Solutions." In ASME Turbo Expo 2014: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/gt2014-25299.
Full textAbstract:
Combined with three-dimensional parameterization method of exhaust diffuser profile, aerodynamic performance evaluation method, response surface approximation evaluation model and Hooke-Jeeves direct search approach, aerodynamic optimization design of exhaust hood diffuser for steam turbine is presented. The aerodynamic performance of exhaust hood design candidate is evaluated using three-dimensional Reynolds-Averaged Navier-Stokes (RANS) solutions. Aerodynamic optimization design of exhaust hood is conducted for the maximum of the static pressure recovery coefficient of exhaust hood. The design variables are specified by the exhaust diffuser profile parameterization method. The aerodynamic performance of the optimized exhaust hood and referenced design is numerically calibrated with consideration of the full last stage and rotor tip clearance. The static pressure recovery coefficient of the optimized exhaust hood is higher than that of the referenced design with consideration of the upstream last stage influence. Furthermore, the detailed flow pattern of the optimized exhaust hood and referenced design is also analyzed and compared.
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Basu, D., A. Hamed, and K. Das. "DES, Hybrid RANS/LES and PANS Models for Unsteady Separated Turbulent Flow Simulations." In ASME 2005 Fluids Engineering Division Summer Meeting. ASMEDC, 2005. http://dx.doi.org/10.1115/fedsm2005-77421.
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This paper presents computational results for two DES (Detached Eddy Simulation), one hybrid RANS (Reynolds Averaged Navier-Stokes)/ LES (Large Eddy Simulation) and some preliminary results from PANS (Partially Averaged Navier-Stokes) turbulence for simulation of unsteady separated turbulent flows. The models are implemented in a full 3-D Navier Stokes solver and are based on the two-equation k-ε model. The formulations of each model are presented and results are analyzed for subsonic flow over a Backward Facing Step (BFS). Simulations are carried out using a 3rd order Roe scheme. A comparative assessment is made between the predictions from the DES, hybrid and PANS models. The predicted results are compared with the available experimental data for skin-friction coefficient, and different turbulent quantities. The three-dimensionality of the flow field and the separated fine scale structures are presented through the Q iso-surfaces.
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Wu, Jiongyang, Wei Shyy, and Stein T. Johansen. "Filter-Based Unsteady RANS Computations for Single-Phase and Cavitating Flows." In ASME 2004 Heat Transfer/Fluids Engineering Summer Conference. ASMEDC, 2004. http://dx.doi.org/10.1115/ht-fed2004-56181.
Full textAbstract:
The widely used Reynolds-Averaged Navier-Stokes (RANS) approach, such as the k-ε two-equation model, has been found to over-predict the eddy viscosity and can dampen out the time dependent fluid dynamics in both single- and two-phase flows. To improve the predictive capability of this type of engineering turbulence closures, a consistent method is offered to bridge the gap between DNS, LES and RANS models. Based on the filter size, conditional averaging is adopted for the Navier-Stokes equation to introduce one more parameter into the definition of the eddy viscosity. Both time-dependent single-phase and cavitating flows are simulated by a pressure-based method and finite volume approach in the framework of the Favre-averaged equations coupled with the new turbulence model. The impact of the filter-based concept, including the filter size and grid dependencies, is investigated using the standard k-ε model and with the available experimental information.