Wall Stress Model Research Articles

Wall-stress boundary conditions for variational-multiscale LES

Two methods are introduced for the implementation of wall-stress boundary conditions in variational-multiscale large-eddy simulations. In both methods, the boundary conditions are applied weakly using an interior-penalty approach, where the discretization parameters are determined using information from a wall-stress model. The performance of the methods is compared with that of hard Dirichlet boundary conditions for turbulent channel flows. A convergence study is performed for the second of the methods, which is found to be the most viable for practical application. Sources of error affecting the convergence study are discussed and quantified. Copyright © 2010 John Wiley & Sons, Ltd.

Boundary-Layer Equation-Based Wall Model for Large-Eddy Simulation of Turbulent Flows with Wall Heat Transfer

A new thermal boundary-layer model is developed that alleviates the stringent near-wall grid resolution requirement in large-eddy simulations of turbulent flows with wall heat transfer. The model is based on solving the turbulent temperature boundary-layer equation to determine the temperature profile in the near-wall region. The near-wall temperature profile is used to compute the instantaneous wall heat flux, which replaces the temperature (Dirichlet) wall boundary condition specified a priori. This approach is analogous to the wall stress model developed by Balaras et al. [1], in which the instantaneous wall shear stresses replace the no-slip wall boundary conditions. Three benchmark turbulent flows are studied using coarse-grid large-eddy simulations coupled with the new thermal wall model: (1) a fully developed turbulent channel flow with a heated top wall, (2) a backward-facing step flow with a heated bottom wall, and (3) an impinging jet on a heated circular plate. Large-eddy simulations are performed using the commercial code CFD-ACE+, with the localized dynamic subgrid kinetic energy model of Kim and Menon [2] providing the subgrid stresses. Turbulence statistics are compared with benchmark data from direct numerical simulations and experiments and also with data from resolved large-eddy simulations (i.e., near-wall y + ≈ 1). Excellent agreement among the data is obtained.

1107 MRT格子ボルツマン法LESの壁面境界モデル(GS-5 乱流(2))

1107 MRT格子ボルツマン法LESの壁面境界モデル(GS-5 乱流(2))

A formulation for near-wall RANS/LES coupling

A near-wall eddy-viscosity formulation for LES is presented. A RANS-like eddy-viscosity corrected with the resolved turbulent stress is imposed in the near-wall region. The RANS eddy-viscosity is obtained from a resolved LES of channel flow at Re τ = 395 and stored in a look-up table. When used with a wall stress model, this technique enables LES to be performed on coarse grids. Results are presented for channel flow at several Reynolds numbers up to Re τ = 10,000. Various issues concerning the numerical behavior of the method are discussed.

Numerical simulation of the flow around a circular cylinder at high Reynolds numbers

The viability and accuracy of large-eddy simulation (LES) with wall modeling for high Reynolds number complex turbulent flows is investigated by considering the flow around a circular cylinder in the supercritical regime. A simple wall stress model is employed to provide approximate boundary conditions to the LES. The results are compared with those obtained from steady and unsteady Reynolds-averaged Navier–Stokes (RANS) solutions and the available experimental data. The LES solutions are shown to be considerably more accurate than the RANS results. They capture correctly the delayed boundary layer separation and reduced drag coefficients consistent with experimental measurements after the drag crisis. The mean pressure distribution is predicted reasonably well at Re D =5×10 5 and 10 6. However, the Reynolds number dependence is not captured, and the solution becomes less accurate at increased Reynolds numbers.