Large eddy simulation of flow over a wall-mounted cube: Comparison of different semi dynamic subgrid scale models

Moustafa Nooroullahi,Mousa Farhadi,Kurosh Sedighi

doi:10.1260/1750-9548.6.1.43

Abstract

In this paper the ability of different semi dynamic subgrid scale models for large eddy simulation was studied in a challenging test case. The semi dynamic subgrid scale models were examined in this investigation is Selective Structure model, Coherent structure model, Wall Adaptive Large Eddy model. The test case is a simulation of flow over a wall-mounted cube in a channel. The results of these models were compared to structure function model, dynamic models and experimental data at Reynolds number 40000. Results show that these semi dynamic models could improve the ability of numerical simulation in comparison with other models which use a constant coefficient for simulation of subgrid scale viscosity. In addition, these models don't have the instability problems of dynamic models.

Highlights

In Large-Eddy Simulation, the flow is divided to resolved scales and subgrid scales
In addition the constant coefficient makes the subgrid scale viscosity acts on whole of domain which is not according to reality, for instance vsgs should be zero in vicinity of wall or in laminar regions
The main purpose of this paper is to investigate the ability of different subgrid scale models which are semi dynamic in simulation of complex phenomena such as horseshoe vortices, flow separation, arc vorticity and etc. for turbulent flow over a wall-mounted cube confined in a channel

Summary

Introduction

In Large-Eddy Simulation, the flow is divided to resolved scales and subgrid scales. The resolved scales are simulated directly and subgrid scales are modeled. There are several methods for simulation subgrid scales such as spectral models, physical space models, deconvolution models and etc. Viscose models are more practical than other models because of their usage in engineering problems. These models are based on this hypothesis “The action of the subgrid scales on the resolved scales is essentially an energetic action, so that the balance of the energy transfers alone between the two scale ranges is sufficient to describe the action of the subgrid scales. The Smagorinsky model is one of famous models in this category In this model the subgrid scale viscosity is defined as: vsgs (x, t) = (Cs∆) S (x, t) 2 1/ 2 ; Cs = 0.18

Objectives

Methods

Results

Conclusion