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 article, an extended period numerical integration of a baroclinic primitive equation model has been made for the simulation and the study of the dynamics of the atmosphere's general circulation, and the solution corresponding to external gravitational propagation is filtered by requiring the vertically integrated divergence to vanish identically.
Abstract: An extended period numerical integration of a baroclinic primitive equation model has been made for the simulation and the study of the dynamics of the atmosphere's general circulation. The solution corresponding to external gravitational propagation is filtered by requiring the vertically integrated divergence to vanish identically. The vertical structure permits as dependent variables the horizontal wind at two internal levels and a single temperature, with the static stability entering as a parameter. The incoming radiation is a function of latitude only corresponding to the annual mean, and the outgoing radiation is taken to be a function of the local temperature. With the requirement for thermal equilibrium, the domain mean temperature is specified as a parameter. The role of condensation is taken into account only as it effectively reduces the static stability. All other external sources and sinks of heat are assumed to balance each other locally, and are thus omitted. The kinematics are th...
12,952 citations
"Evaluation of LES models for flow o..." refers background in this paper
...Ever since Smagorinsky (1963) proposed first model 1 for the SGS stresses, many newer models have been developed....
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...2.1 Conventional smagorinsky model Smagorinsky (1963) proposed the first subgrid-scale stress model....
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...Ever since Smagorinsky (1963) proposed the first model for the SGS stresses, many newer models have been developed....
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... Smagorinsky (1963) proposed the first subgrid-scale stress model....
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06 Jan 1992
8,784 citations
TL;DR: In this article, a new eddy viscosity model is presented which alleviates many of the drawbacks of the existing subgrid-scale stress models, such as the inability to represent correctly with a single universal constant different turbulent fields in rotating or sheared flows, near solid walls, or in transitional regimes.
Abstract: One major drawback of the eddy viscosity subgrid‐scale stress models used in large‐eddy simulations is their inability to represent correctly with a single universal constant different turbulent fields in rotating or sheared flows, near solid walls, or in transitional regimes. In the present work a new eddy viscosity model is presented which alleviates many of these drawbacks. The model coefficient is computed dynamically as the calculation progresses rather than input a priori. The model is based on an algebraic identity between the subgrid‐scale stresses at two different filtered levels and the resolved turbulent stresses. The subgrid‐scale stresses obtained using the proposed model vanish in laminar flow and at a solid boundary, and have the correct asymptotic behavior in the near‐wall region of a turbulent boundary layer. The results of large‐eddy simulations of transitional and turbulent channel flow that use the proposed model are in good agreement with the direct simulation data.
6,747 citations
TL;DR: In this paper, the subgrid-scale closure method developed by Germano et al. is modified by use of a least squares technique to minimize the difference between the closure assumption and the resolved stresses.
Abstract: The subgrid‐scale closure method developed by Germano et al. is modified by use of a least squares technique to minimize the difference between the closure assumption and the resolved stresses. This modification removes a source of singularity and is believed to improve the method’s applicability.
3,730 citations
TL;DR: In this article, the three-dimensional, primitive equations of motion have been integrated numerically in time for the case of turbulent, plane Poiseuille flow at very large Reynolds numbers.
Abstract: The three-dimensional, primitive equations of motion have been integrated numerically in time for the case of turbulent, plane Poiseuille flow at very large Reynolds numbers. A total of 6720 uniform grid intervals were used, with sub-grid scale effects simulated with eddy coefficients proportional to the local velocity deformation. The agreement of calculated statistics against those measured by Laufer ranges from good to marginal. The eddy shapes are examined, and only the u-component, longitudinal eddies are found to be elongated in the downstream direction. However, the lateral v eddies have distinct downstream tilts. The turbulence energy balance is examined, including the separate effects of vertical diffusion of pressure and local kinetic energy.It is concluded that the numerical approach to the problem of turbulence at large Reynolds numbers is already profitable, with increased accuracy to be expected with modest increase of numerical resolution.
1,868 citations
"Evaluation of LES models for flow o..." refers background in this paper
...…study, numerical values of 0·13 and 0·094 have been set forCS andCk respectively to account appropriately for the energy in the resolvable turbulence (Deardorff 1970).1 is the filter width (grid size), and is the characteristic length scale of the largest subgrid-scale eddies and is taken to be…...
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