The numerical simulation of high Reynolds number flows is hampered by model accuracy if the Reynolds-averaged Navier–Stokes (RANS) equations are used, and by computational cost if direct or large-eddy simulations (LES) that resolve the near-wall layer are employed. The cost of a calculation scales like the Reynolds number to the power 3 for direct numerical simulations, or 2.4 for LES, making the resolution of the wall layer at high Reynolds number infeasible even with the most advanced computers. In LES, an attractive alternative to compute high-Re flows is the use of wall-layer models, in which only the outer layer is resolved, while the near-wall region is modeled. Three broad classes of approaches are presently used: bypassing this region altogether using wall functions, solving a separate set of equations in the near-wall region, weakly coupled to the outer flow, or simulating the near-wall region in a global, Reynolds-averaged, sense. These approaches are discussed and their ranges of applicability are highlighted. Various unresolved issues in wall-layer modeling are presented.

Wall-layer models for large-eddy simulations

This paper presents a reformulated version of the author'sk-ω model of turbulence. Revisions include the addition of just one new closure coefficient and an adjustment to the dependence of eddy viscosity on turbulence properties. The result is a significantly improved model that applies to both boundary layers and free shear flows and that has very little sensitivity to finite freestream boundary conditions on turbulence properties. The improvements to the k-ω model facilitate a significant expansion of its range of applicability. The new model, like preceding versions, provides accurate solutions for mildly separated flows and simple geometries such as that of a backward-facing step. The model's improvement over earlier versions lies in its accuracy for even more complicated separated flows. This paper demonstrates the enhanced capability for supersonic flow into compression corners and a hypersonic shock-wave/ boundary-layer interaction. The excellent agreement is achieved without introducing any compressibility modifications to the turbulence model.

Formulation of the k-w Turbulence Model Revisited

Hybrid LES/RANS methods for the simulation of turbulent flows

Recent advances on the numerical modelling of turbulent flows

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

Hybrid LES-RANS: A one-equation SGS Model combined with a κ - ω model for predicting recirculating flows

http://publications.lib.chalmers.se/records/fulltext/180053/local_180053.pdf

Shia-Hui Peng

Papers

Hybrid LES-RANS: A one-equation SGS Model combined with a κ - ω model for predicting recirculating flows

Quantitative numerical analysis of flow past a circular cylinder at Reynolds number between 50 and 200

Large Eddy Simulation for Turbulent Buoyant Flow in a Confined Cavity

On a Subgrid-Scale Heat Flux Model for Large Eddy Simulation of Turbulent Thermal Flow

An improved k−ω turbulence model applied to recirculating flows