大小涡旋分开考虑的模式理论

近年来,k-ε模式普遍流行,但它是一种梯度形式的模式理论。由于湍流涡旋的衰减时间极长,在一般的流动问题中,上游产生的大涡旋或附近产生的大涡旋在到达当地时还远远没有衰减掉,因此会对当地的流动产生很大的影响。根据不可逆热力学理论的基本原理,必须准平衡、准定常和小偏离的情形下,才能使用梯度形式的流和力的关系式。一般说来这对大涡旋是并不满足的,所以k-ε模式的应用有着很大的局限性。本文根据湍流的实际情况,把湍流脉动分成大涡旋和小涡旋两个组成部份,并且把大涡旋部份再分成局部产生的和上游流来或扩散过来的两个组成部份,这样就得到了由三个部份组成的湍流模式理论。

A New Turbulence Model with the Separate Consideration of Large and Small Vortexes

Recently the k-ε model has been widely used, but it is a kind of gradient model. Because the life-time of turbulence vortexes is very long, in common flow problems the influence of up-stream vortexes must be important, and the vortexes are not in quasi-equilibrium. So the usefulness of the k-ε model and other gradient models is limited. In this paper, according to actual cases of the turbulence, the velocity fluctuations are separated into large and small vortexes, and the large vortexes consist of two parts, one comes from up-stream end around, the other is locally generated. Thus we get a turbulence model, which consists of three parts.