湍流的粘性和频散效应

本文应用Prandtl混合长理论导得了既包含湍流粘性又包含湍流频散的新的Reynolds平均运动方程组.分析指出:(1)湍流不仅存在粘性效应,而且存在频散效应;(2)正是湍流的频散效应可能导致能量逆转(即常说的负粘性现象,实质为一定条件下的负频散现象),并给出了能量逆转的必要条件和充分条件;(3)给出了湍流的KdV-Burgers方程模型.

Dissipation and Dispersion Effects of Turbulence

This paper uses the Prandtl 's mixing length theory to derive a set of new Reynolds averaged equations which contain both the dissipation and dispersion effects. It is shown that (a) There-exist not only the dissipation but also the-dispersion effects in the turbulent flow (b) It is the dispersion effect of the turbulence that results in the energy inversion which under certain conditions represents a negative dispersion phenomena which is usually miscalled the negative viscosity pheromena. The necessary and sufficient conditions of the energy inversion are obtained (c) A KdV-Burgers equation model of the turbulence is presented.