Direct numerical simulation of turbulent flow over backward-facing at high Reynolds numbers

Abstract

Direct numerical simulation (DNS) was performed for the first time to study the flow over a backward-facing step at a high Reynolds number on a coarse grid. The flow over backward-facing step is the typical turbulent flow controlled by large eddy, in which the effect of small eddy could be negligible as an approximation. The grid dimension could easily satisfy the resolution requirement to describe the characteristics of a large eddy flow. Therefore, direct numerical simulation of N-S equations to obtain the turbulent flow field on the coarse grid could be realized. Numerical simulation of a two-dimensional flow over a backward-facing step at a Reynolds number Re=44000 was conducted using Euler-Lagrange finite element scheme based on the efficient operator-splitting method (OSFEM). The flow field was descretized by triangle meshes with 16669 nodes. The overall computational time only took 150 min on a PC. Both the characteristics of time-averaged and instantaneous turbulent flow were simultaneously obtained. The analysis showed that the calculated results were in good agreement with the test data. Hence, the DNS approach could become the reality to solve the complex turbulent flow with high Reynolds numbers in practical engineering.