Evaluation of LES models for flow over bluff body from engineering application perspective
01 Feb 2005-Sadhana-academy Proceedings in Engineering Sciences (Springer India)-Vol. 30, Iss: 1, pp 11-20
TL;DR: In this article, three SGS stress closure LES models are evaluated for turbulent flow over a square cylinder and it is concluded that a one-equation model for subgrid kinetic energy is the best choice.
Abstract: Three SGS stress closure LES models are evaluated for turbulent flow over a square cylinder. Emphasis is placed on solving engineering-application-type problems on affordable computer resources and within reasonable turnaround times. Results are compared with available experimental data and previously published workshop results. Numerical strategies are kept the same for all the cases. Results are also discussed keeping in view limitations of LES methodology of modelling for practical problems and current developments. It is concluded that a one-equation model for subgrid kinetic energy is the best choice.
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TL;DR: A coupled diffuse interface lattice Boltzmann fluid flow solver and a diffuse interface heat transfer approach are combined in view of dealing with even more convoluted geometries, incorporating the dynamics of interfaces and complex multiphysics applications.
21 citations
TL;DR: In this article, a nonlinear eddy viscosity model (NLEVM) and a scalable hybrid Reynolds averaged Navier-Stokes/ large eddy simulation (RANS/LES) strategy are developed to improve the capability of the EVM to simulate complex flows.
Abstract: A non-linear eddy viscosity model (NLEVM) and a scalable hybrid Reynolds averaged Navier-Stokes/ large eddy simulation (RANS/LES) strategy are developed to improve the capability of the eddy viscosity model (EVM) to simulate complex flows featuring separations and unsteady motions To study the performance of the NLEVM, numerical simulations around S809 airfoil are carried out and the results show that the NLEVM performs much better when a large separation occurs Calculated results of the flow around a triangular cylinder show that the NLEVM can improve the precision of the flow fields to some extents, but the error is still considerable, and the small turbulence structures can not be clearly captured as the EVM Whereas the scalable hybrid RANS/LES model based on the NLEVM is fairly effective on resolving the turbulent structures and can give more satisfactory predictions of the flow fields
18 citations
Dissertation•
01 Jan 2009
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16 citations
TL;DR: In this article, some of the issues involved in performing hybrid LES reported in the recent literature is briefly reviewed, as well as an alternative solu- tion suggested was to combine RANS and LES, which in general referred to as Hybrid LES.
Abstract: In the late eighties and up to the beginning of nineties computation of turbulent flows is mostly dominated by RANS (Reynolds Averaged Navier-Stokes Simulation) type modelling. During the last few years URANS (Unsteady RANS) and LES (Large Eddy Simulation) type of approaches have been attempted with some success. Yet, there have been many difficulties when LES is applied to practi- cal engineering problems and to high Reynolds number flows as energy dissipating eddies become really small and mesh resolution required for a reasonably resolved LES approaches that of DNS (Direct Numerical Simulation). An alternative solu- tion suggested was to combine RANS and LES, which in general referred to as Hybrid LES. There have been many proposals for combining RANS and LES in different ways. In this article, some of the issues involved in performing hybrid LES reported in the recent literature is briefly reviewed.
9 citations
Cites methods from "Evaluation of LES models for flow o..."
...In a parallel attempt, a Hybrid LES using a one-equation model for flow with massive separation was also carried out ( Vengadesan & Nakayama, 2005 )....
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...In a parallel attempt, a Hybrid LES using a one-equation model for flow with massive separation was also carried out (Vengadesan & Nakayama, 2005)....
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TL;DR: In this article, the authors showed that the effectiveness of flow separation control using Electro-Magneto-Hydro-Dynamic (EMHD) method can be improved by choosing the dimensions of the actuator based on the Reynolds number and the shape of the model studied.
Abstract: The present numerical study shows that the effectiveness of flow separation control using Electro-Magneto-Hydro-Dynamic (EMHD) method can be improved by choosing the dimensions of the actuator based on the Reynolds number and the shape of the model studied. The width of the electrode/magnet for most effective flow separation control should be approximately 2.5 times the boundary layer thickness, which in turn is dependent on the Reynolds number. The length of the EMHD actuator for most effective flow separation control can be the shortest based on manufacturing constraints as well as on the possibility of shifting of separation point. The application of Lorentz force inside the boundary layer near the separation point provides the most effective flow separation control. The studies are done for flow over a cylinder in low Reynolds number regime (Reynolds number = 200) and for flow over an elliptical airfoil in high Reynolds number regime (Reynolds number = 1.6 × 105).
6 citations
References
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TL;DR: In this paper, a hybrid LES-RANS modeling approach is proposed, where RANS is used in the near wall regions (y ≤ 60), and the turbulence is modelled with a κ-ω model.
Abstract: A hybrid LES-RANS modelling approach is proposed. RANS is used in the near wall regions (y ≤ 60), and the turbulence is modelled with a κ-ω model. LES is used in the remaining part of the flow, and the SGS turbulence is modelled with a one-equation κ sgs model. The same continuity and momentum equations are solved throughout the domain, the only difference being that the turbulent viscosity is taken from the κ-ω model in the RANS region, and from the one-equation κ sgs model in the LES region. The new modelling approach is applied to two incompressible flow test cases. They are fully developed flow in a plane channel and the flow over a 2D-hill in a channel
191 citations
"Evaluation of LES models for flow o..." refers methods in this paper
...This hybrid approach is now being attempted using various other RANS models like Menter SST model (Stretlets 2001), multiscalek − ε model (Nichols & Nelson 2003) and low Rek − ω model (Davidson & Peng 2003)....
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Book•
01 Jan 1978
TL;DR: The three dimensional, time dependent (incompressible) vorticity equations were used to simulate numerically the decay of isotropic box turbulence and time developing mixing layers as discussed by the authors.
Abstract: The three dimensional, time dependent (incompressible) vorticity equations were used to simulate numerically the decay of isotropic box turbulence and time developing mixing layers. The vorticity equations were spatially filtered to define the large scale turbulence field, and the subgrid scale turbulence was modeled. A general method was developed to show numerical conservation of momentum, vorticity, and energy. The terms that arise from filtering the equations were treated (for both periodic boundary conditions and no stress boundary conditions) in a fast and accurate way by using fast Fourier transforms. Use of vorticity as the principal variable is shown to produce results equivalent to those obtained by use of the primitive variable equations.
180 citations
TL;DR: In this article, a large eddy simulation (LES) was used to study the turbulent plane channel flow and cyclic boundary conditions were imposed on velocity and pressure in downstream and spanwise directions.
Abstract: Turbulent plane channel flow is numerically studied using Large Eddy Simulation(LES). Cyclic boundary conditions are imposed on velocity and pressure in the downstream and spanwise directions. The noslip boundary condition is imposed on the walls. Both Smagorinsky model and 1-equation model are applied, and the comparison is made. The importance of the diffusion term in subgrid scale (SGS) turbulent energy balance is pointed out.
105 citations
"Evaluation of LES models for flow o..." refers methods in this paper
...2.3 One-equation model One-equation for subgrid-scale kinetic energy was proposed by Yoshizawa & Horiuti (1985)....
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...This model was used by Horiuti (1985) for channel flow to study the budget for subgrid-scale kinetic energy....
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TL;DR: In this article, the authors proposed a modification to the two-parameter dynamic procedure for wall bounded flows, which removes that defect and ensures that the mixed model provides proper wall shear stress and mean velocity profile.
Abstract: It is well known that the correlation between the Smagorinsky model and the subgrid scale stress is low, while the model based on the scale similarity assumption has considerably higher correlation. However, the scale similarity model by itself was found to be insufficiently dissipative. Therefore, the model is usually used together with the Smagorinsky model. Model coefficients are commonly computed using the two-parameter dynamic procedure. Nevertheless, the dynamic two-parameter mixed model still does not work well for wall bounded flows, since the model predicts a high value of the wall shear stress. In this study, we propose a modification to the two-parameter dynamic procedure for wall bounded flows, which removes that defect: the Smagorinsky parameter, CS, is computed exactly the same way as in the dynamic Smagorinsky model, then the other parameter, CL, is computed dynamically as CS is known. This ensures that the mixed model provides proper wall shear stress and mean velocity profile. Computation...
79 citations