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
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433 citations
"Evaluation of LES models for flow o..." refers result in this paper
...Besides, these strategies are also close to those of a participant of the workshop (TAMU2 of Rodi et al 1997)....
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TL;DR: In this article, a large eddy simulation (LES) model is compared with the Subgrid Scale (SGS) model for Taylor Re numbers between 35 and 248 using various SGS models, representative of the contemporary state of the art.
Abstract: Recently, a number of studies have indicated that Large Eddy Simulation (LES) models are fairly insensitive to the adopted Subgrid Scale (SGS) models. In order to study this and to gain further insight into LES, simulations of forced and decaying homogeneous isotropic turbulence have been performed for Taylor Re numbers between 35 and 248 using various SGS models, representative of the contemporary state of the art. The predictive capability of the LES concept is analyzed by comparison with DNS data and with results obtained from a theoretical model of the energy spectrum. The resolved flow is examined by visualizing the morphology and by analyzing the distribution of resolved enstrophy, rate of strain, stretching, SGS kinetic energy, and viscosity. Furthermore, the correlation between eigenvalues of the resolved rate of strain tensor and the vorticity is investigated. Although the gross features of the flow appear independent of the SGS model, pronounced differences between the models become apparent whe...
283 citations
TL;DR: In this article, the phase-averaged velocities and turbulence intensities of the turbulent shear layer and the associated recirculation region on the sidewall formed in flow separation from the forward corner of a square cylinder have been studied with one-component laser-Doppler velocimetry.
Abstract: The turbulent shear layer and the associated recirculation region on the sidewall formed in flow separation from the forward corner of a square cylinder have been studied with one-component laser-Doppler velocimetry. Because of vortex shedding, the flow is approximately periodic, and is treated as a separated flow undergoing largeamplitude forcing at the shedding frequency. Phase (ensemble)-averaged velocities and turbulence intensities were obtained, and a close relationship in phase and amplitude between phase-averaged turbulence intensities and gradients of phase-averaged velocity is found in much of the flow region. The similarity behaviour of the phase-averaged profiles in the shear layer as well as the streamwise growth of the shear layer are investigated. While phase-averaged velocity profiles collapse well in similarity coordinates, normalized turbulence intensities exhibit systematic deviations from similarity. Shear-layer growth also departs markedly from the linear growth law of unforced plane mixing layers. The effect of the recirculation is suggested as a possible explanation for some of these deviations. Similarities to and differences from steady and forced mixing layers, steady separated flows with recirculation, and unsteady boundary layers are discussed.
259 citations
"Evaluation of LES models for flow o..." refers background in this paper
...A standard benchmark test case of turbulent flow over square cylinder at Reynolds number Re = 22, 000 ( Lyn & Rodi 1994, Lyn et al 1995) is considered for comparison....
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...A standard benchmark test case of turbulent flow over square cylinder at Reynolds number Re = 22, 000 (Lyn & Rodi 1994, Lynet al 1995) is considered for comparison....
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TL;DR: In this paper, a dynamic subgrid-scale stress model is proposed for finite-difference large-eddy simulation of incompressible and compressible flows in which the Leonard and cross-parts of the SGS stress tensor are assumed to be proportional to the resolved part, which is computed explicity.
Abstract: This work focuses on subgrid‐scale (SGS) modeling for finite‐difference large‐eddy simulations, employing filters in physical space. When a filter in physical space is used, an overlap is allowed between the unresolved and the resolved scales. For such a filter, all the three terms in the classical decomposition of the SGS stress tensor are present: the Leonard and cross‐terms, due to the overlap between scales, and the true SGS Reynolds tensor, expressing the pure effect of the small scales. A dynamic subgrid‐scale stress model is proposed, for finite‐difference large‐eddy simulation of incompressible and compressible flows in which the Leonard and cross‐parts of the SGS stress tensor are assumed to be proportional to the resolved part (the ‘‘modified Leonard term’’), which is computed explicity. The SGS Reynolds stress is modeled by the eddy‐viscosity Smagorinsky model. The two unknown parameters in this model are computed dynamically, as in Germano et al. [Phys. Fluids A 3, 1790 (1991)], but using a least squares technique. The model is tested using direct numerical simulation data for fully developed turbulent incompressible flows in presence of solid boundaries and free surfaces, and for compressible homogeneous turbulence. A ‘‘box filter’’ in physical space is used. Other SGS models are also tested, viz. the dynamic model of Germano et al. (DSM), and its compressible extension by Moin et al. [Phys. Fluids A 3, 2746 (1991)], and the dynamic mixed model in Zang et al. [Phys. Fluids A 5, 3186 (1993)] (DMM) and its compressible version developed here. Results on the behavior of the different models with regard to energy exchanges and correlation with the exact SGS stresses are presented for different filter widths. In particular high correlation is found between the modified Leonard and cross‐terms thus justifying the basic assumption made in the model.
233 citations
"Evaluation of LES models for flow o..." refers background in this paper
...Recently, Morinishi & Vasilyev (2001) proposes another model with suggestion on the existing dynamic twoparameter mixed SGS model of Salvetti & Banerjee (1995)....
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...Recently, Morinishi & Vasilyev (2001) proposes another model with suggestion on the existing dynamic twoparameter mixed SGS model of Salvetti & Banerjee (1995) ....
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01 Jan 2003
TL;DR: In this paper, a hybrid LES-RANS modelling approach is proposed, where RANS is used in the near wall regions (y +. 60), and the turbulence is modelled with a k-! model.
Abstract: SUMMARY 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 k-! model. LES is used in the remaining part of theow, and the SGS turbulence is modelled with a one-equation ksgs model. The same continuity and momentum equations are solved throughout the domain, the only dierence being that the turbulent viscosity is taken from the k-! model in the RANS region, and from the one-equation ksgs model in the LES region. The new modelling approach is applied to two incompressibleow test cases. They are fully developedow in a plane channel and theow over a 2D-hill in a channel. Copyright ? 2003 John Wiley & Sons, Ltd.
205 citations