不可压缩湍流的多尺度模型

Multiscale model for incompressible turbulent flows

基于可变时间间隔平均方法,提出了一种不可压缩湍流多尺度模型及平均流动方程.与传统的单尺度湍流模型不同,该模型在建立的过程中,保留了湍流的多尺度特性,结合平均流动方程,可以更好地预测湍流流场特征.通过模拟平面后台阶流动和不对称平板扩压器流动,并将预测结果与标准k-ε模型的预测结果对比,初步验证了其可信性及优越性.结果表明:计算所得的平面后台阶流动的流向再附长度与台阶边压力系数比比标准k-ε模型提高精度约20%;平板扩压器流动的回流区位置误差约为7%、倾斜壁面摩擦因数误差约为5%,而标准k-ε模型未能预测出分离现象.可以看出该模型适用于典型的分离流动,在湍流流场的预测中表现优异。

A multiscale model based on variable interval time average method and a set of averaged equations for incompressible turbulent flows were presented.Unlike traditional turbulence models,the multiscale characteristics of turbulent flows were researved during establishment,and more accurate prediction of the flow field was given.The credibility of this model was verified through numerical simulation of the flow over a back-facing step and the flow in an asymmetric plane diffuser.The reattachment length and the surface pressure coefficient on step-side wall for the flow over a back-facing step were closer to the experimental results than the results that calculated with the standard k-ε model, which is almost 20%. The error of the position of the recirculation zone for the flow in an asymmetric plane diffuser is almost 7%, and the error of the frictional resistance coefficient on inclined wall is almost 5%, while the flow separation could not be predicted using the standard k-ε model.Results show that this model is suitable for separated flows, and gives a more accurate prediction of flow field, so this model is useful in engineering application.