Comparative assessment of SAS, IDDES and hybrid filtering RANS/LES models based on second-moment closure

Guangxue Wang,Hao Li,Shengye Wang,Wei Liu,Xiang Fu

doi:10.1177/16878140211028447

Abstract

The question of which turbulence model is better for a given class of applications is always confusing for the CFD researchers and users. Comparative assessments of scale-adaptive simulation (SAS), improved delay detached-eddy simulation (IDDES) and other hybrid RANS/LES models based on eddy-viscosity models (EVMs) are thoroughly investigated. But how well they perform based on a second-moment closure needs to be answered. In this paper, a widely acclaimed Reynolds-stress model (RSM) in aeronautical engineering, SSG/LRR-[Formula: see text] model, is carried out. The relevant test cases include the NACA0012 airfoil stalled flows and turret separated flow. In order to make a more reasonable comparison, a seventh-order scheme WCNS-E8T7 is adopted to reduce the influence of the numerical dissipation and a symmetrical conservative metric method is used to ensure the robustness. By comparing with the relevant experimental data and the solutions by original SSG/LRR-[Formula: see text] model (etc. URANS), it shows that all of the three hybrid methods (SAS, IDDES and hybrid filtering methods) based on the SSG/LRR-[Formula: see text] model have a good ability to simulate unsteady turbulence. Among them, the IDDES correction has the most potential.

Highlights

For computational fluid dynamics (CFD), the predicted result of arbitrary flow simulation depends on the appropriation of the underlying representation of flow physics and the accuracy of the numerical method solving the corresponding equations.[1]
Both approaches behave like a subgrid-stress transport model when the turbulent length scale is greater than the grid length scale, and the dissipation equation is decoupled from the turbulence-stress equations in this region
A comparative assessment of SSG/LRR-scale-adaptive simulation (SAS), SSG/ LRR-improved delay detached-eddy simulation (IDDES) and hybrid SSG/LRR models is made with the high-order weighed compact nonlinear scheme (WCNS)-E8T7 scheme

Summary

Introduction

For computational fluid dynamics (CFD), the predicted result of arbitrary flow simulation depends on the appropriation of the underlying representation of flow physics and the accuracy of the numerical method solving the corresponding equations.[1]. Navier-Stokes equations,[17] and revised for compressible flow.[7] The hybrid filtering method includes two critical factors: turbulence model (including RANS model and LES model) and blending function. The hybrid operator defined in equation (22) is applied to the original Navier-Stokes equations, and generate extra equations for hybrid variables These extra terms were found to ensure a proper transfer of momentum in RANS to LES transition region, avoid incorporating artificial stochastic forcing. Seven partial different equations for the Reynolds stresses R^ij, specific dissipation rate v are required in the SSG/LRR-v model, whereas only six equations for the subgrid-scale (or subfilter-scale) stresses (SGS) R^sijgs is employed in the LES Combining these within the hybrid RANS/LES framework, a new hybrid turbulence-stress term R^hijyb can be defined as follows: R^hijyb = FR^rijans + ð1 À FÞR^sijgs ð23Þ. The F2 blending function initially proposed by Menter for the SST model has been successfully applied by Sanchez-Rocha and Menon[7] and is repeated here: pffiffiffiffiffiffiffi

Numerical methods

Conclusions