Effects of Inflow Mach Number and Step Height on Supersonic Flows over a Backward-Facing Step

Haixu Liu,Yincheng Guo,Wenyi Lin,Huiqiang Zhang,Bing Wang

doi:10.1155/2013/147916

Abstract

The backward-facing step is practically implicated in many devices, encountering the massive separation flows. In the present study, simulations of supersonic flow over a backward-facing step have been carried out employing both RANS and LES. The simulated results are validated against the experimental data. The results of RANS and LES show a good comparison with the experimental results. Different inflow Mach numbers and expansion ratios are also investigated. The reattachment length decreases with the increase of inflow Mach number. The duct height has a great effect on the flow patterns. The present conclusions are helpful to understand the physics in supersonic separation flows and also provide theory basis for engineering applications.

Highlights

The flow over backward-facing step is one of the important prototypes used to study the separation flows
Le et al [2] found that the velocity-pressure and viscous diffusion are negligible in the shear layer, but both are significant in the near-wall region by direct numerical simulation of the backward-facing step
We present two different RANS models which are k-ε and k-ω turbulence models while Smagorinsky SGS model is used for LES

Summary

Introduction

The flow over backward-facing step is one of the important prototypes used to study the separation flows. Yang et al [17] performed a detailed theoretical investigation of the flow structure in a supersonic flow over a backward-facing step, and they employed a flux-vector splitting lower-upper symmetric successive over relaxation (LU-SSOR) scheme to solve the governing equations numerically and algebraic eddyviscosity model of Baldwin-Lomax for turbulence closure. They got reasonable agreement between calculated results and the experimental data. The effects of inflow Mach number and expansion ratio on reattachment length are studied

Methodology

Results and Discussions

Conclusions