Journal articles: '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.Â 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.

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Kinnas, Spyros A. "VIScous Vorticity Equation (VISVE) for Turbulent 2-D Flows with Variable Density and Viscosity." Journal of Marine Science and Engineering 8, no. 3 (March 11, 2020): 191. http://dx.doi.org/10.3390/jmse8030191.

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The general vorticity equation for turbulent compressible 2-D flows with variable viscosity is derived, based on the Reynolds-Averaged Navier-Stokes (RANS) equations, and simplified versions of it are presented in the case of turbulent or cavitating flows around 2-D hydrofoils.

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Borello, D., G. Delibra, K. Hanjalić, and F. Rispoli. "Large-eddy simulations of tip leakage and secondary flows in an axial compressor cascade using a near-wall turbulence model." Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 223, no. 6 (July 6, 2009): 645–55. http://dx.doi.org/10.1243/09576509jpe825.

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This paper reports on the application of unsteady Reynolds averaged Navier—Stokes (U-RANS) and hybrid large-eddy simulation (LES)/Reynolds averaged Navier—Stokes (RANS) methods to predict flows in compressor cascades using an affordable computational mesh. Both approaches use the ζ— f elliptic relaxation eddy-viscosity model, which for U-RANS prevails throughout the flow, whereas for the hybrid the U-RANS is active only in the near-wall region, coupled with the dynamic LES in the rest of the flow. In this ‘seamless’ coupling the dissipation rate in the k-equation is multiplied by a grid-detection function in terms of the ratio of the RANS and LES length scales. The potential of both approaches was tested in several benchmark flows showing satisfactory agreement with the available experimental results. The flow pattern through the tip clearance in a low-speed linear cascade shows close similarity with experimental evidence, indicating that both approaches can reproduce qualitatively the tip leakage and tip separation vortices with a relatively coarse computational mesh. The hybrid method, however, showed to be superior in capturing the evolution of vortical structures and related unsteadiness in the hub and wake regions.

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Morton, Scott, James Forsythe, Anthony Mitchell, and David Hajek. "Detached-Eddy Simulations and Reynolds-Averaged Navier-Stokes Simulations of Delta Wing Vortical Flowfields." Journal of Fluids Engineering 124, no. 4 (December 1, 2002): 924–32. http://dx.doi.org/10.1115/1.1517570.

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An understanding of vortical structures and vortex breakdown is essential for the development of highly maneuverable vehicles and high angle of attack flight. This is primarily due to the physical limits these phenomena impose on aircraft and missiles at extreme flight conditions. Demands for more maneuverable air vehicles have pushed the limits of current CFD methods in the high Reynolds number regime. Simulation methods must be able to accurately describe the unsteady, vortical flowfields associated with fighter aircraft at Reynolds numbers more representative of full-scale vehicles. It is the goal of this paper to demonstrate the ability of detached-eddy Simulation (DES), a hybrid Reynolds-averaged Navier-Stokes (RANS)/large-eddy Simulation (LES) method, to accurately predict vortex breakdown at Reynolds numbers above 1×106. Detailed experiments performed at Onera are used to compare simulations utilizing both RANS and DES turbulence models.

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Sun, M. B., J. H. Liang, and Z. G. Wang. "A modified blending function for zonal hybrid Reynolds-averaged Navier—Stokes/large-eddy simulation methodology." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 223, no. 8 (August 1, 2009): 1067–81. http://dx.doi.org/10.1243/09544100jaero575.

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A modified blending function for zonal hybrid Reynolds averaged Navier—Stokes/large eddy simulation (RANS/LES) methodology was developed using an empirical analogy from Menter k—ω shear stress transport (SST) turbulent model (Menter, 1994) to predict complex turbulent flows. Tests of slot jet in supersonic flow and supersonic flow over compression—expansion ramp was conducted and prediction of separations was well improved when certain model constant was forced on the traditional blending function (Baurle et al., 2003). Analysis based on calculations of flat plate boundary layer demonstrated that an efficient empirical constant could be used in blending function and boundary layer could be well calculated without heavy contamination of RANS on wake region. Validation of the modified zonal hybrid RANS/LES approach for slot jet in supersonic flow, supersonic flow over compression—expansion ramp, supersonic flow over backward facing step, and supersonic cavity flow was conducted. The simulated results showed that the modified blending function performs well on complex turbulent flows. Deficiencies of traditional hybrid zonal RANS/LES method in over-prediction of separations associated with adverse pressure gradient flows were favourably improved.

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Che Sidik, Nor Azwadi, Siti Nurul Akmal Yusuf, Yutaka Asako, Saiful Bahri Mohamed, and Wan Mohd Arif Aziz Japa. "A Short Review on RANS Turbulence Models." CFD Letters 12, no. 11 (November 30, 2020): 83–96. http://dx.doi.org/10.37934/cfdl.12.11.8396.

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Reynolds-Averaged Navier-Stokes (RANS) are such model equations and are used to simulate numerous fluid flow problem. This article focuses on the most well-known of RANS turbulence modelling and its application to industrial flows. Among all the RANS models, low Reynold number (LRN) turbulence model is more accurate that the standard turbulence model. This paper intends to provide a brief review of researches on RANS turbulence modelling for the fundamental understanding in solving fluid flow problem and identifies opportunities for future research.

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Korpus, R. A., and J. M. Falzarano. "Prediction of Viscous Ship Roll Damping by Unsteady Navier-Stokes Techniques." Journal of Offshore Mechanics and Arctic Engineering 119, no. 2 (May 1, 1997): 108–13. http://dx.doi.org/10.1115/1.2829050.

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This paper describes a numerical technique for analyzing the viscous unsteady flow around oscillating ship hulls. The technique is based on a general Reynolds-averaged Navier-Stokes (RANS) capability, and is intended to generate viscous roll moment data for the incorporation of real-flow effects into potential flow ship motions programs. The approach utilizes the finite analytic technique for discretizing the unsteady RANS equations, and a variety of advanced turbulence models for closure. The calculations presented herein focus on viscous and vortical effects without free-surface, and utilize k-epsilon turbulence modeling. Series variations are presented to study the effects of frequency, amplitude, Reynolds number, and the presence of bilge keels. Moment component breakdown studies are performed in each case to isolate the effects of viscosity, vorticity, and potential flow pressures.

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Ling, Julia, Andrew Kurzawski, and Jeremy Templeton. "Reynolds averaged turbulence modelling using deep neural networks with embedded invariance." Journal of Fluid Mechanics 807 (October 18, 2016): 155–66. http://dx.doi.org/10.1017/jfm.2016.615.

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There exists significant demand for improved Reynolds-averaged Navier–Stokes (RANS) turbulence models that are informed by and can represent a richer set of turbulence physics. This paper presents a method of using deep neural networks to learn a model for the Reynolds stress anisotropy tensor from high-fidelity simulation data. A novel neural network architecture is proposed which uses a multiplicative layer with an invariant tensor basis to embed Galilean invariance into the predicted anisotropy tensor. It is demonstrated that this neural network architecture provides improved prediction accuracy compared with a generic neural network architecture that does not embed this invariance property. The Reynolds stress anisotropy predictions of this invariant neural network are propagated through to the velocity field for two test cases. For both test cases, significant improvement versus baseline RANS linear eddy viscosity and nonlinear eddy viscosity models is demonstrated.

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Hsiao, C. T., and G. L. Chahine. "Numerical Study of Cavitation Inception Due to Vortex/Vortex Interaction in a Ducted Propulsor." Journal of Ship Research 52, no. 02 (June 1, 2008): 114–23. http://dx.doi.org/10.5957/jsr.2008.52.2.114.

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Cavitation inception in a ducted propulsor was studied numerically using Navier-Stokes computations and bubble dynamics models. Experimental observations of the propulsor model and previous numerical computations using Reynolds-averaged Navier-Stokes (RANS) codes indicated that cavitation inception occurred in the region of interaction of the leakage and trailing tip vortices. The RANS simulations failed, however, to predict correctly both the cavitation inception index value and the inception location. To improve the numerical predictions, we complemented here the RANS computations with a direct Navier-Stokes simulation in a reduced computational domain including the region of interaction of the two vortices. Initial and boundary conditions in the reduced domain were provided by the RANS solution of the full ducted propulsor flow. Bubble nuclei were released in this flow field, and spherical and nonspherical bubble dynamics models were exercised to investigate cavitation inception. This resulted in a solution in much better agreement with the experimental measurements than the original RANS solution. Both the value of the cavitation inception index and the location of the cavitation inception were very well captured. The characteristics of the emitted acoustic signals and of the bubble shapes during a cavitation event were also computed.

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Kranenborg, Joost, Geert Campmans, Niels Jacobsen, Jebbe van der Werf, Robert McCall, Ad Reniers, and Suzanne Hulscher. "RANS MODELLING OF CROSS-SHORE SEDIMENT TRANSPORT AND MORPHODYNAMICS IN THE SWASH-ZONE." Coastal Engineering Proceedings, no. 36v (December 28, 2020): 14. http://dx.doi.org/10.9753/icce.v36v.sediment.14.

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Most numerical studies of sediment transport in the swash zone use depth-averaged models. However, such models still have difficulty predicting transport rates and morphodynamics. Depth-resolving models could give detailed insight in swash processes but have mostly been limited to hydrodynamic predictions. We present a depth-resolving numerical model, based on the Reynolds Averaged Navier-Stokes (RANS) equations, capable of modelling sediment transport and morphodynamics in the swash zone.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/PB8Vs0LJq88

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Foures, Dimitry P. G., Nicolas Dovetta, Denis Sipp, and Peter J. Schmid. "A data-assimilation method for Reynolds-averaged Navier–Stokes-driven mean flow reconstruction." Journal of Fluid Mechanics 759 (November 4, 2014): 404–31. http://dx.doi.org/10.1017/jfm.2014.566.

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AbstractWe present a data-assimilation technique based on a variational formulation and a Lagrange multipliers approach to enforce the Navier–Stokes equations. A general operator (referred to as the measure operator) is defined in order to mathematically describe an experimental measure. The presented method is applied to the case of mean flow measurements. Such a flow can be described by the Reynolds-averaged Navier–Stokes (RANS) equations, which can be formulated as the classical Navier–Stokes equations driven by a forcing term involving the Reynolds stresses. The stress term is an unknown of the equations and is thus chosen as the control parameter in our study. The data-assimilation algorithm is derived to minimize the error between a mean flow measurement and the measure performed on a numerical solution of the steady, forced Navier–Stokes equations; the optimal forcing is found when this error is minimal. We demonstrate the developed data-assimilation framework on a test case: the two-dimensional flow around an infinite cylinder at a Reynolds number of $\mathit{Re}=150$. The mean flow is computed by time-averaging instantaneous flow fields from a direct numerical simulation (DNS). We then perform several ‘measures’ on this mean flow and apply the data-assimilation method to reconstruct the full mean flow field. Spatial interpolation, extrapolation, state vector reconstruction and noise filtering are considered independently. The efficacy of the developed identification algorithm is quantified for each of these cases and compared with more traditional methods when possible. We also analyse the identified forcing in terms of unsteadiness characterization, present a way to recover the second-order statistical moments of the fluctuating velocities and finally explore the possibility of pressure reconstruction from velocity measurements.

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Zou, Qingping, Zhong Peng, and Pengzhi Lin. "EFFECTS OF WAVE BREAKING AND BEACH SLOPE ON TOE SCOUR IN FRONT OF A VERTICAL SEAWALL." Coastal Engineering Proceedings 1, no. 33 (December 28, 2012): 122. http://dx.doi.org/10.9753/icce.v33.sediment.122.

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Scour in front of coastal structures is a major threat to structural stability and safety of properties behind. In this study, a Reynolds Averaged Navier-Stokes Solver (RANS) is combined with a Volume of Fluid (VOF) (RANS-VOF) surface capturing scheme to investigate the wave interactions with a Seawall and its adjacent sea bed. The main objective is to investigate the effects of wave breaking and beach slope on toe scour in front of a vertical wall.

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Davidson, Lars. "Hybrid LES–RANS: back scatter from a scale-similarity model used as forcing." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 367, no. 1899 (July 28, 2009): 2905–15. http://dx.doi.org/10.1098/rsta.2008.0299.

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A dissipative scale-similarity subgrid model was recently proposed in which only the dissipative part of the subgrid stresses was added to the momentum equations. This was achieved by adding the gradient of a subgrid stress only when its sign agreed with that of the corresponding viscous term. In the present work, this idea is used the other way around as forcing in hybrid large eddy simulation–Reynolds-averaged Navier–Stokes: only the part of a subgrid stress term that corresponds to back scatter is added to the momentum equations. The forcing triggers resolved turbulence in the transition region between the unsteady Reynolds-averaged Navier–Stokes and large eddy simulation regions. The new approach is evaluated for fully developed channel flow at Re τ =4000. It is found that the forcing indeed does increase the resolved turbulence in the transition region. The magnitude of the production (i.e. back scatter) due to forcing in the equation for resolved kinetic energy is of the order of that due to the usual strain-rate production term. The present approach of using back scatter from a scale-similarity model can also probably be useful for triggering transition.

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Reliquet, Gabriel, Marie Robert, Lionel Gentaz, and Pierre Ferrant. "Simulations de l'interaction entre le catamaran Delft 372 et la houle à l'aide du couplage SWENSE-Level Set." La Houille Blanche, no. 5-6 (December 2019): 59–66. http://dx.doi.org/10.1051/lhb/2019030.

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Ce papier présente les derniers développements concernant le couplage de la méthode SWENSE (Spectral Waves Navier-Stokes Equations) et d'une méthode de résolution des équations RANS (Reynolds Averaged Navier-Stokes) avec capture d'interface de type Level Set. Ce couplage permet de combiner les avantages des deux méthodes, c'est-à-dire avoir une cinématique de houle de bonne qualité dans tout le domaine grâce à la méthode SWENSE et la prise en compte du déferlement via la fonction Level Set. Le catamaran Delft 372 est utilisé pour les validations avec des calculs sur mer calme et sur houle régulière à deux vitesses différentes.

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Sakthivel, R., S. Vengadesan, and S. K. Bhattacharyya. "Application of non-linear k-e turbulence model in flow simulation over underwater axisymmetric hull at higher angle of attack." Journal of Naval Architecture and Marine Engineering 8, no. 2 (November 22, 2011): 149–63. http://dx.doi.org/10.3329/jname.v8i2.6984.

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This paper addresses the Computational Fluid Dynamics Approach (CFD) to simulate the flow over underwater axisymmetric bodies at higher angle of attacks. Three Dimensional (3D) flow simulation is carried out over MAYA Autonomous Underwater Vehicle (AUV) at a Reynolds number (Re) of 2.09×106. These 3D flows are complex due to cross flow interaction with hull which produces nonlinearity in the flow. Cross flow interaction between pressure side and suction side is studied in the presence of angle of attack. For the present study standard k-ε model, non-linear k-ε model models of turbulence are used for solving the Reynolds Averaged Navier-Stokes Equation (RANS). The non-linear k-ε turbulence model is validated against DARPA Suboff axisymmetric hull and its applicability for flow simulation over underwater axisymmetric hull is examined. The non-linear k-ε model performs well in 3D complex turbulent flows with flow separation and flow reattachment. The effect of angle of attack over flow structure, force coefficients and wall related flow variables are discussed in detail. Keywords: Computational Fluid Dynamics (CFD); Autonomous Underwater Vehicle (AUV); Reynolds averaged Navier-Stokes Equation (RANS); non-linear k-ε turbulence modeldoi: http://dx.doi.org/10.3329/jname.v8i2.6984 Journal of Naval Architecture and Marine Engineering 8(2011) 149-163

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Lindau, Jules W., Robert F. Kunz, David A. Boger, David R. Stinebring, and Howard J. Gibeling. "High Reynolds Number, Unsteady, Multiphase CFD Modeling of Cavitating Flows." Journal of Fluids Engineering 124, no. 3 (August 19, 2002): 607–16. http://dx.doi.org/10.1115/1.1487360.

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A preconditioned, homogeneous, multiphase, Reynolds Averaged Navier-Stokes model with mass transfer is presented. The model is preconditioned in order to obtain good convergence and accuracy regardless of phasic density ratio or flow velocity. Engineering relevant validative unsteady two and three-dimensional results are given. A demonstrative three-dimensional, three-field (liquid, vapor, noncondensable gas) transient is also presented. In modeling axisymmetric cavitators at zero angle-of-attack with 3-D unsteady RANS, significant asymmetric flow features are obtained. In comparison with axisymmetric unsteady RANS, capture of these features leads to improved agreement with experimental data.

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Rogalev, A. N., N. D. Rogalev, V. O. Kindra, S. K. Osipov, and A. S. Zonov. "Numerical study of heat transfer in rectangular channels with single pin fin and pin fin-dimple." E3S Web of Conferences 124 (2019): 01010. http://dx.doi.org/10.1051/e3sconf/201912401010.

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Evaluation of the heat transfer and hydraulic performance of a new pin fin-dimple cooling system in a rectangular channel shows its advantage. The performance are compared with the pin fin system ones with 3-D Reynolds averaged Navier-Stokes (RANS) equations. The fluid flow and heat transfer analysis for the Reynolds numbers from 8000 to 70000 involved the shear stress transport turbulence model. The new system forms a high-intensity vortex around the pin fin-dimple that increases the near-wall turbulent mixing level that intensifies the heat transfer. The calculation results indicate increases of the averaged Nusselt number and the averaged friction factor of 7–13% and 7–12% respectively against the pin fin.

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Kumar, K. Siva, and Sharanappa V. Sajjan. "Unsteady Flow past a Combined Pitching and Plunging Aerofoil Using an Implicit RANS Solver." Applied Mechanics and Materials 110-116 (October 2011): 3481–88. http://dx.doi.org/10.4028/www.scientific.net/amm.110-116.3481.

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Unsteady Reynolds-averaged Navier-Stokes (RANS) computations are presented for low Mach number flow past a combined pitching and plunging NACA 0012 aerofoil. The Implicit RANS solver used for obtaining time-accurate solutions is based on a finite volume nodal point spatial discretization scheme with dual time stepping. The aim is to validate the unsteady solver for flapping motion of the aerofoil. Results are presented in the form of aerodynamic coefficients and compared with available literature, thus demonstrating the capability of the solver to provide useful unsteady input data for aeroelastic and aeroacoustic analysis.

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Kumar, K. Siva, and Sharanappa V. Sajjan. "Unsteady Compressible Flow over Heaving Bodies Using an Implicit RANS Solver." Applied Mechanics and Materials 110-116 (October 2011): 4589–97. http://dx.doi.org/10.4028/www.scientific.net/amm.110-116.4589.

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Unsteady Reynolds-Averaged Navier-Stokes computations are presented for the flow over a pure plunging aerofoil and a plunging wing. The implicit RANS solver used for obtaining time-accurate solution is based on implicit finite volume nodal point spatial discretization scheme with dual time stepping. Baldwin and Lomax turbulence model has been used for the turbulence closure. The results are obtained in the form of aerodynamic coefficients, thrust coefficient and propulsion efficiency for two different cases over the aerofoil and wing and are compared with available literature.

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Chamanara, Mehdi, Hassan Ghassemi, Manouchehr Fadavie, and Mohammad Aref Ghassemi. "Effects of the Duct Angle and Propeller Location on the Hydrodynamic Characteristics of the Ducted Propeller." Ciencia y tecnología de buques 11, no. 22 (March 20, 2018): 41. http://dx.doi.org/10.25043/19098642.162.

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In the present study, the effect of the duct angle and propeller location on the hydrodynamic characteristics of the ducted propeller using Reynolds-Averaged Navier Stokes (RANS) method is reported. A Kaplan type propeller is selected with a 19A duct. The ducted propeller is analyzed by three turbulence models including the k-ε standard, k-ω SST and Reynolds stress model (RSM). The numerical results are compared with experimental data. The effects of the duct angle and the location of the propeller inside the propeller are presented and discussed.

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Teles, Maria João, António Pires-Silva, and Michel Benoit. "THE INFLUENCE OF THE TURBULENCE CLOSURE MODEL ON WAVE-CURRENT INTERACTION MODELING AT A LOCAL SCALE AT A LOCAL SCALE." Coastal Engineering Proceedings 1, no. 33 (October 18, 2012): 64. http://dx.doi.org/10.9753/icce.v33.waves.64.

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An advanced CFD solver based on the RANS (Reynolds Averaged Navier-Stokes) equations is used to evaluate wave-current interactions through numerical simulations of combined wave-current free surface turbulent flows. The repercussions of various schemes for modeling turbulence effects is addressed with a special attention to the exchanges and fluxes of momentum and energy between the mean flow components and the wave (oscillatory) component. Numerical simulations are compared with experimental data from Klopman (1994).

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Díaz-Carrasco, Pilar, Sergio Croquer, Vahid Tamimi, Jay Lacey, and Sébastien Poncet. "Advances in Numerical Reynolds-Averaged Navier–Stokes Modelling of Wave-Structure-Seabed Interactions and Scour." Journal of Marine Science and Engineering 9, no. 6 (June 2, 2021): 611. http://dx.doi.org/10.3390/jmse9060611.

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This review paper presents the recent advances in the numerical modelling of wave–structure–seabed interactions. The processes that are involved in wave–structure interactions, which leads to sediment transport and scour effects, are summarized. Subsequently, the three most common approaches for modelling sediment transport that is induced by wave–structure interactions are described. The applicability of each numerical approach is also included with a summary of the most recent studies. These approaches are based on the Reynolds-Averaged Navier–Stokes (RANS) equations for the fluid phase, and mostly differ in how they tackle the seabed response. Finally, future prospects of research are discussed.

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Ivanov, Nikolay, Marina Zasimova, Evgueni Smirnov, and Detelin Markov. "Evaluation of mean velocity and mean speed for test ventilated room from RANS and LES CFD modeling." E3S Web of Conferences 85 (2019): 02004. http://dx.doi.org/10.1051/e3sconf/20198502004.

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The paper presents and discusses data for the ventilation airflow in an isothermal room corresponding to the Nielsen et al. (1978) test computed with Large Eddy Simulation (LES) and Reynolds-Averaged Navier-Stokes (RANS) approaches. As LES computations provide directly both the speed and velocity components data, the difference between the mean speed and mean velocity values is computed and discussed. For the RANS computations that give the mean velocity data only, application of the velocity-to-speed conversion procedure based on the turbulence kinetic energy field provided by a turbulence model resulted in accurate mean speed evaluation.

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Česenek, Jan. "Space-time discontinuous Galerkin method for the numerical simulation of viscous compressible gas flow with the k-omega turbulence model." EPJ Web of Conferences 180 (2018): 02016. http://dx.doi.org/10.1051/epjconf/201818002016.

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In this article we deal with the numerical simulation of the non-stationary compressible turbulent flow described by the Reynolds-Averaged Navier-Stokes (RANS) equations. This RANS system is equipped with two-equation k-omega turbulence model. The discretization of these two systems is carried out separately by the space-time discontinuous Galerkin method. This method is based on the piecewise polynomial discontinuous approximation of the sought solution in space and in time. We use the numerical experiments to demonstrate the applicability of the shown approach. All presented results were computed with the own-developed code.

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Sauca, Ana Camelia, Tudor Milchiș, and Ferdinánd-Zsongor Gobesz. "Wind Loading on Solar Panels." Műszaki Tudományos Közlemények 10, no. 1 (April 1, 2019): 73–78. http://dx.doi.org/10.33894/mtk-2019.10.10.

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Abstract A fully 3D numerical analysis of turbulent flow over a cluster of solar photovoltaic (PV) panels was performed in order to assess the total drag and lift forces, comparing the results with the values from the guidelines of the national standard. A Reynolds-Averaged Navier–Stokes (RANS) model was used in the numerical simulations, considering two acting directions of the wind along the length of the array (0 degree – front, and 180 degrees – reverse direction).

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Lasher, William C., and Peter J. Richards. "Validation of Reynolds-Averaged Navier-Stokes Simulations for International America’s Cup Class Spinnaker Force Coefficients in an Atmospheric Boundary Layer." Journal of Ship Research 51, no. 01 (March 1, 2007): 22–38. http://dx.doi.org/10.5957/jsr.2007.51.1.22.

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Three semirigid models for International America's Cup Class spinnakers were tested in a wind tunnel with a simulated atmospheric boundary layer. These experiments were also simulated using a commercial Reynolds-averaged Navier-Stokes (RANS) solver with three different turbulence models. A comparison between the experimental and numerical force coefficients shows very good agreement. The experimentally measured differences in the driving force coefficients among the three sails were predicted well by all three turbulence models. The realizable k-e model produced the best results, and the standard k-e model produced the worst. The Reynolds stress model did not perform significantly better than the standard k-e model. The results suggest that RANS can be used as a design tool for optimizing spinnaker shape.

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Larsen, Bjarke Eltard, and David R. Fuhrman. "On the over-production of turbulence beneath surface waves in Reynolds-averaged Navier–Stokes models." Journal of Fluid Mechanics 853 (August 23, 2018): 419–60. http://dx.doi.org/10.1017/jfm.2018.577.

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In previous computational fluid dynamics studies of breaking waves, there has been a marked tendency to severely over-estimate turbulence levels, both pre- and post-breaking. This problem is most likely related to the previously described (though not sufficiently well recognized) conditional instability of widely used turbulence models when used to close Reynolds-averaged Navier–Stokes (RANS) equations in regions of nearly potential flow with finite strain, resulting in exponential growth of the turbulent kinetic energy and eddy viscosity. While this problem has been known for nearly 20 years, a suitable and fundamentally sound solution has yet to be developed. In this work it is demonstrated that virtually all commonly used two-equation turbulence closure models are unconditionally, rather than conditionally, unstable in such regions. A new formulation of the $k$–$\unicode[STIX]{x1D714}$ closure is developed which elegantly stabilizes the model in nearly potential flow regions, with modifications remaining passive in sheared flow regions, thus solving this long-standing problem. Computed results involving non-breaking waves demonstrate that the new stabilized closure enables nearly constant form wave propagation over long durations, avoiding the exponential growth of the eddy viscosity and inevitable wave decay exhibited by standard closures. Additional applications on breaking waves demonstrate that the new stabilized model avoids the unphysical generation of pre-breaking turbulence which widely plagues existing closures. The new model is demonstrated to be capable of predicting accurate pre- and post-breaking surface elevations, as well as turbulence and undertow velocity profiles, especially during transition from pre-breaking to the outer surf zone. Results in the inner surf zone are similar to standard closures. Similar methods for formally stabilizing other widely used closure models ($k$–$\unicode[STIX]{x1D714}$ and $k$–$\unicode[STIX]{x1D700}$ variants) are likewise developed, and it is recommended that these be utilized in future RANS simulations of surface waves. (In the above $k$ is the turbulent kinetic energy density, $\unicode[STIX]{x1D714}$ is the specific dissipation rate, and $\unicode[STIX]{x1D700}$ is the dissipation.)

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Rogowski, Krzysztof, and Martin O. L. Hansen. "RANS Simulations of Flow Past an DU-91-W2-250 Airfoil at High Reynolds Number." E3S Web of Conferences 44 (2018): 00150. http://dx.doi.org/10.1051/e3sconf/20184400150.

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This paper presents numerical results of the DU-91-W2-250 airfoil. Reynolds-averaged Navier–Stokes (RANS) simulations of the 2D profile are performed employing the Transient SST turbulence model. The airfoil was investigated for the Reynolds number of 6 106. Lift and drag coefficients are compared with the experimental data from LM Low Speed Wind Tunnel (LSWT). The results of lift and drag coefficients obtained using the SST Transient model are in a good agreement in comparison with the experiment in the angle of attack range from -10° to 10°. The static pressure distributions calculated by the SST Transition model are also in good agreement with the experiment.

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38

Bozinoski, Radoslav, and Roger L. Davis. "A DES Procedure Applied to a Wall-Mounted Hump." International Journal of Aerospace Engineering 2012 (2012): 1–11. http://dx.doi.org/10.1155/2012/149461.

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This paper describes a detached-eddy simulation (DES) for the flow over a wall-mounted hump. The Reynolds number based on the hump chord isRec=9.36×105with an in-let Mach number of 0.1. Solutions of the three-dimensional Reynolds-averaged Navier-Stokes (RANS) procedure are obtained using the Wilcoxk−ωequations. The DES results are obtained using the model presented by Bush and Mani and are compared with RANS solutions and experimental data from NASA's 2004 Computational Fluid Dynamics Validation on Synthetic Jets and Turbulent Separation Control Workshop. The DES procedure exhibited a three-dimensional flow structure in the wake, with a 13.65% shorter mean separation region compared to RANS and a mean reattachment length that is in good agreement with experimental measurements. DES predictions of the pressure coefficient in the separation region also exhibit good agreement with experiment and are more accurate than RANS predictions.

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Herrera-Granados, Oscar. "Numerical Analysis of Flow Behavior in a Rectangular Channel with Submerged Weirs." Water 13, no. 10 (May 17, 2021): 1396. http://dx.doi.org/10.3390/w13101396.

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In this contribution, different 3D numerical approaches are applied in order to simulate the behaviour of turbulent flow through a rectangular channel with broad-crested weirs. In addition, water flow velocities, using Acoustic Doppler Velocimetry (ADV) instrumentation, were recorded. Two turbulence quantities are estimated using the laboratory records and were compared with those computed with the Large Eddy Simulation (LES) and Reynolds Averaged Navier–Stokes (RANS) models. Additionally, a quadrant analysis of the laboratory records was carried out. The output of the models presents good agreement with the time-averaged parameters, but is not sufficient for the proper estimation of the turbulence quantities.

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Amicarelli, Andrea, Annalisa Di Bernardino, Franco Catalano, Giovanni Leuzzi, and Paolo Monti. "Analytical Solutions of the Balance Equation for the Scalar Variance in One-Dimensional Turbulent Flows under Stationary Conditions." Advances in Mathematical Physics 2015 (2015): 1–13. http://dx.doi.org/10.1155/2015/424827.

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This study presents 1D analytical solutions for the ensemble variance of reactive scalars in one-dimensional turbulent flows, in case of stationary conditions, homogeneous mean scalar gradient and turbulence, Dirichlet boundary conditions, and first order kinetics reactions. Simplified solutions and sensitivity analysis are also discussed. These solutions represent both analytical tools for preliminary estimations of the concentration variance and upwind spatial reconstruction schemes for CFD (Computational Fluid Dynamics)—RANS (Reynolds-Averaged Navier-Stokes) codes, which estimate the turbulent fluctuations of reactive scalars.

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Jones, David, Dominic Reeve, and Qingping Zou. "THE EFFECT OF EMBANKMENT CREST WIDTH ON COMBINED OVERFLOW AND WAVE OVERTOPPING." Coastal Engineering Proceedings 1, no. 33 (October 18, 2012): 28. http://dx.doi.org/10.9753/icce.v33.structures.28.

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In this paper a Reynolds-averaged Navier-Stokes based wave model (RANS) has been used to investigate how the discharge caused by combined overflow and wave overtopping of embankments is influenced by embankment crest width. The results demonstrate that embankments with a narrower crest width can expect significantly increased discharge in accordance with that expected for flow over weirs. The experimental results have been used to explain the difference in discharge found with the current design formulae for combined overflow and wave overtopping.

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Hafid, Mohamed. "Numerical Study of a Turbulent Burner by Means of RANS and Detailed Chemistry." International Journal of Energetica 3, no. 2 (January 2, 2019): 34. http://dx.doi.org/10.47238/ijeca.v3i2.76.

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The present paper shows a numerical study of the Co-flow turbulent flame configuration using the Reynolds Averaged Navier-Stokes (RANS) modelling with detailed chemistry. The presumed Probability Density Function (PDF) model combined with the k-Ɛ turbulence model is adopted. The GRI Mech-3.0 mechanism that involves 53 species and 325 reactions is used. The effect of the turbulent Schmidt number Sct and the C1ε constant in the turbulent dissipation transport equation is highlighted. Despite the simplicity of RANS approach compared to other complex models such as LES and DNS, the results show that this approach is still able to simulate the turbulent flame.

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dos Santos, Elizaldo Domingues, Marco Paulsen Rodrigues, Thiago Smith V. C. de Andrade, Liércio André Isoldi, Francis Henrique Ramos França, and Luiz Alberto Oliveira Rocha. "Numerical Study of Different Closure Approaches for Prediction of Forced Convective Turbulent Cylindrical Cavity Flows." Defect and Diffusion Forum 366 (April 2016): 166–81. http://dx.doi.org/10.4028/www.scientific.net/ddf.366.166.

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The present work exhibits a numerical study comparing the fluid dynamic and thermal fields of turbulent, three-dimensional forced convective cylindrical cavity flows obtained with Large Eddy Simulation (LES) and Reynolds-Averaged Navier Stokes (RANS). In the latter approach, three different closure models are employed: Reynolds Stress Model (RSM), standard k – ε and standard k - ω. It is considered a three-dimensional, incompressible, turbulent fluid flow at the steady state with ReD = 22,000 and Pr = 0.71. The main purpose is to investigate whether discrepancies are noticed in time-averaged and statistics of turbulent flows between LES and RANS predictions. Differences in time-averaged and statistical fields can be important for evaluation of convective fluxes in turbulent flows and combined convective and radiative transfer in participant media, i.e., for study of Turbulence-Radiation Interactions (TRI). The spatially-filtered and time-averaged conservation equations of mass, momentum and energy are solved with the Finite Volume Method (FVM). Results showed that time-averaged and RMS thermal fields obtained with LES and RANS presented reasonable discrepancies in regions near the cavity surfaces, which affects the convective fluxes in this region. For the highest temperature region of the cavity (near its inlet) the predictions obtained with LES and RANS are similar, which can led to similar predictions in heat exchange when thermal radiation is taken into account in optically thin participant media. For optically thick media, where local differences increase their importance, the employment of RANS is not recommended.

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Papamoschou, Dimitri. "Modelling of noise reduction in complex multistream jets." Journal of Fluid Mechanics 834 (November 17, 2017): 555–99. http://dx.doi.org/10.1017/jfm.2017.730.

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The paper presents a low-order prediction scheme for the noise change in multistream jets when the nozzle geometry is altered from a known baseline. The essence of the model is to predict the changes in acoustics due to the redistribution of the mean flow as computed by a Reynolds-averaged Navier–Stokes (RANS) solver. A RANS-based acoustic analogy framework is developed that addresses the noise in the polar direction of peak emission and uses the Reynolds stress as a time-averaged representation of the action of the coherent turbulent structures. The framework preserves the simplicity of the Lighthill acoustic analogy, using the free-space Green’s function, while accounting for azimuthal effects via special forms for the space–time correlation combined with source–observer relations based on the Reynolds stress distribution in the jet plume. Results are presented for three-stream jets with offset secondary and tertiary flows that reduce noise in specific azimuthal directions. The model reproduces well the experimental noise reduction trends. Principal mechanisms of noise reduction are elucidated.

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Cremades Rey, Luis F., Denis F. Hinz, and Mahdi Abkar. "Reynolds Stress Perturbation for Epistemic Uncertainty Quantification of RANS Models Implemented in OpenFOAM." Fluids 4, no. 2 (June 22, 2019): 113. http://dx.doi.org/10.3390/fluids4020113.

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Reynolds-averaged Navier-Stokes (RANS) models are widely used for the simulation of engineering problems. The turbulent-viscosity hypothesis is a central assumption to achieve closures in this class of models. This assumption introduces structural or so-called epistemic uncertainty. Estimating that epistemic uncertainty is a promising approach towards improving the reliability of RANS simulations. In this study, we adopt a methodology to estimate the epistemic uncertainty by perturbing the Reynolds stress tensor. We focus on the perturbation of the turbulent kinetic energy and the eigenvalues separately. We first implement this methodology in the open source package OpenFOAM. Then, we apply this framework to the backward-facing step benchmark case and compare the results with the unperturbed RANS model, available direct numerical simulation data and available experimental data. It is shown that the perturbation of both parameters successfully estimate the region bounding the most accurate results.

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Leschziner, Michael, Ning Li, and Fabrizio Tessicini. "Simulating flow separation from continuous surfaces: routes to overcoming the Reynolds number barrier." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 367, no. 1899 (July 28, 2009): 2885–903. http://dx.doi.org/10.1098/rsta.2009.0002.

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This paper provides a discussion of several aspects of the construction of approaches that combine statistical (Reynolds-averaged Navier–Stokes, RANS) models with large eddy simulation (LES), with the objective of making LES an economically viable method for predicting complex, high Reynolds number turbulent flows. The first part provides a review of alternative approaches, highlighting their rationale and major elements. Next, two particular methods are introduced in greater detail: one based on coupling near-wall RANS models to the outer LES domain on a single contiguous mesh, and the other involving the application of the RANS and LES procedures on separate zones, the former confined to a thin near-wall layer. Examples for their performance are included for channel flow and, in the case of the zonal strategy, for three separated flows. Finally, a discussion of prospects is given, as viewed from the writer's perspective.

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Gomatam, Sreekar, S. Vengadesan, and S. K. Bhattacharyya. "Numerical simulations of flow past an autonomous underwater vehicle at various drift angles." Journal of Naval Architecture and Marine Engineering 9, no. 2 (December 24, 2012): 135–52. http://dx.doi.org/10.3329/jname.v9i2.12567.

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Three dimensional (3D) flow past an Autonomous Underwater Vehicle (AUV) is simulated using a Computational Fluid Dynamics (CFD) approach at a Reynolds (Re) number of 2.09x106. A non-linear k-? (NLKE) turbulence model is used for solving the Reynolds Averaged Navier-Stokes (RANS) equations. The effect of control surfaces over the flow, the flow interaction between the hull and the appendages at various Angles of Attack (AoA) and the effect of the symmetry plane is studied. Flow structure, variation of flow variables and force distribution for various AoA are presented and discussed in detail.DOI: http://dx.doi.org/10.3329/jname.v9i2.12567 Journal of Naval Architecture and Marine Engineering 9(2012) 135-152

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Novkovic, Djordje, Jela Burazer, Aleksandar Cocic, and Milan Lecic. "On the influence of turbulent kinetic energy level on accuracy of k − ε and LRR turbulence models." Theoretical and Applied Mechanics 45, no. 2 (2018): 139–49. http://dx.doi.org/10.2298/tam171201009n.

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This paper presents research regarding the influence of turbulent kinetic energy (TKE) level on accuracy of Reynolds averaged Navier?Stokes (RANS) based turbulence models. A theoretical analysis of influence TKE level on accuracy of the RANS turbulence models has been performed according to the Boussinesq hypothesis definition. After that, this theoretical analysis has been investigated by comparison of numerically and experimentally obtained results on the test case of a steady-state incompressible swirl-free flow in a straight conical diffuser named Azad diffuser. Numerical calculations have been performed using the OpenFOAM CFD software and first and secondorder closure turbulence models. TKE level, velocity profiles and Reynolds stresses have been calculated downstream in four different cross sections of the diffuser. Certain conclusions about modeling turbulent flows by ?? ??? and LRR turbulence models have been made by comparing the velocity profiles, TKE distribution and Reynolds stresses on the selected cross sections.

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Nouri, N. M., S. M. H. Mirsaeedi, and M. Moghimi. "Large eddy simulation of natural cavitating flows in Venturi-type sections." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 225, no. 2 (June 23, 2010): 369–81. http://dx.doi.org/10.1243/09544062jmes2036.

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Large eddy simulation (LES) is used here to model the cavitating flow at a Venturi-type section. Cavitating flows can occur in a wide range of applications. The flow is represented here by means of LES, which compared to Reynolds-averaged Navier—Stokes (RANS) has the advantage that in it the large, energy-containing structures are resolved directly, whereas most of these structures are modelled in RANS. This gives LES an improved fidelity over RANS, although, due to the time averaging, the required computational time is considerably lower for RANS than for LES. The conclusion of this work shows that the qualitative comparisons with earlier preliminary data and the simulated general cavitation behaviour correlate reasonably well with experimental observations and that the simulations have the ability to predict cavitation cycle in more detail.

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Werner, Sofia, Alessio Pistidda, Lars Larsson, and Björn Regnstrom. "Computational Fluid Dynamics Validation for a Fin/Bulb/Winglet Keel Configuration." Journal of Ship Research 51, no. 04 (December 1, 2007): 343–56. http://dx.doi.org/10.5957/jsr.2007.51.4.343.

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A wind tunnel test of an America's Cup keel model is used for validation of one Reynolds-averaged Navier Stokes (RANS) code and one potential flow/boundary layer code. The effects of grid size, stagnation point anomaly, and turbulence model on the RANS results are discussed. Various setups of the potential code are compared. The ability of both methods to predict forces and trends are shown. The errors of the RANS code are slightly larger than the experimental error, whereas the potential flow/boundary layer results are within the experimental uncertainty, provided that a correct panelization is used. A comparison of the experimental wake flow pattern to the one computed with RANS is presented. The k-w turbulence model is shown to give the best predictions of the wake.

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Journal articles on the topic 'RANS (Reynolds-Averaged Navier-Stokes)'

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