一种适于强分离流动的三方程VLES模型

A three-equation VLES model for strongly separated flow

强分离流动的准确模拟对湍流模型极具挑战性,导致现有的VLES模型仍难以满足要求。究其原因,强分离流动往往伴随分离涡且具有局部旋转特征,而现有模型往往并未考虑该效应。为此,该文基于旋转湍流中表现优异的k-ω-v~2模型,建立了一种新的VLES模型,并将其应用于圆柱绕流中,结果表明:相比现有的VLES k-ε模型,新模型准确地预测了圆柱后方的回流区长度,且雷诺应力的预测明显占优。通过精度控制函数及几个相关尺度的分析,发现湍流积分尺度是关键影响因素,新模型得到了该尺度的合理值,而VLES k-ε模型则高估了该值,导致精度控制函数偏低而预测失真。

Accurate simulation of strongly separated flow is challenging for turbulence models,making present VLES models hard to reach the requirement.The reason is that the strongly separated flow is often accompanied by separated vortices and has local rotation characteristics,but the existing models often do not consider this effect.Therefore,in this paper,a new VLES is constructed and applied to the flow around a circular cylinder,based on the k-ω-v~2 model which behaves well enough in rotating turbulence.The results show that:compared with the existing VLES k-ε model,the new model accurately predicts the length of the recirculation zone behind the cylinder,and the prediction of Reynolds stress is obviously superior.Through the analysis of the resolution control function and several related scales,it is found that the turbulence integral scale is the key factor.The new model obtains a reasonable value of this scale,while the VLES k-ε model overestimates this value,which led to low resolution control function and prediction distortion.