不可压缩流体后台阶紊流特性的计算与分析

Computation and Analysis of Turbulent Characteristics in Incompressible Fluid Flow Past Backward-facing Step

后台阶紊流是一种几何形式简单,但含有复杂紊流结构的流动,利用RNGκ-ε模型计算分析后台阶紊流特性。选取雷诺数Re为2000、5000、10000、20000四种紊流工况进行模拟,比较分析了紊动能、紊动能耗散率、紊动强度、紊动粘性系数等反映紊流特性的参数。结果表明,紊动能、耗散率、紊动强度随雷诺数的增大而增大,受后台阶流动分离区的影响各参数呈现一定的断面分布特征,据此重点探讨了紊动粘性系数与紊动强度、速度梯度等参数之间的内在关系,提出了紊动粘性系数计算公式的改进形式,这对于研究创新紊流模型具有促进作用。

The turbulent flow over backward-facing step is a kind of flow which contains complex turbulent structure with a simple geometry.The RNGκ-ε model was used to simulate the turbulent characteristics of backward-facing step flow.The turbulent conditions of four Reynolds numbers of Re=2000,5000,10000,and 20000 were selected for simulation.The turbulent kinetic energy,turbulent dissipation rate,turbulence intensity,turbulent viscous coefficient and other parameters reflecting the turbulent characteristics were compared.The results show that the turbulent kinetic energy,dissipation rate and turbulence intensity increase with the increase of Reynolds number,and the section profiles of the above parameters are affected by the flow separation region downstream the step.Based on the numerical results,the intrinsic relationships between the turbulent viscous coefficient and the parameters such as turbulence intensity and velocity gradient were discussed,and an improved form of the calculation formula of turbulent eddy viscous coefficient was proposed,which is of great significance to the study and development of new turbulence model.