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速度梯度张量的拉格朗日演化模型一般使用Kolmogorov时间作为演化的无量纲时间。Yu和Meneveau的研究证实,在均匀各向同性湍流中,采用各子区域的当地Kolmogorov时间对应变率张量的拉格朗日时间自相关函数(以下简称自相关函数)进行无量纲化后,不同子区域的自相关函数的下降曲线会相互重合,这说明各向同性湍流中速度梯度张量演化的无量纲时间是当地Kolmogorov时间。本文使用大涡模拟的方法,对雷诺数7000的槽道湍流进行类似的研究,以到壁面的无量纲距离y(10)的大小将流场分为不同区间,使用当地Kolmogorov时间进行无量纲化。发现不同y(10)区间自相关函数的下降曲线不完全重合:在对数区中不同y(10)区间自相关函数的下降曲线基本重合,但在靠近壁面的粘性底层和过渡层中则无此现象。因此,当地Kolmogorov时间不是槽道中速度梯度张量演化的普适无量纲时间。
The Lagrange evolution model of velocity gradient tensor generally uses Kolmogorov time as evolutionary dimensionless time. The study of Yu and Meneveau confirms that in the homogeneous isotropic turbulence, the local Kolmogorov time of each subregion is used to conduct the dimensionless Lagrange time autocorrelation function (hereinafter referred to as autocorrelation function) of the strain rate tensor, The descending curves of autocorrelation functions of different subregions coincide with each other, which shows that the dimensionless time of velocity gradient tensor evolution in isotropic turbulence is the local Kolmogorov time. In this paper, a large eddy simulation method is used to simulate the channel turbulence in a Reynolds number of 7000. The flow field is divided into different intervals by the dimensionless distance y (10) of the wall and is dimensionless using the local Kolmogorov time . It is found that the descending curves of autocorrelation functions in different y (10) intervals do not completely coincide: the descending curves of autocorrelation functions in different y (10) intervals are basically coincident in the logarithmic zone, but not in the viscous bottom and transitional layers close to the wall This phenomenon. Therefore, the local Kolmogorov time is not a universal, dimensionless time for the evolution of the velocity gradient tensor in the channel.