Large‐ and small‐scale stirring of vorticity and a passive scalar in a 3‐D temporal mixing layer
Large‐ and small‐scale stirring of vorticity and a passive scalar in a 3‐D temporal mixing layer
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3D 时间混合层中涡度和被动标量的大尺度和小尺度搅拌
DOI：
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发表时间：
1991
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通讯作者：
E. Lamballais
中科院分区：
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作者：
P. Comte;M. Lesieur;E. Lamballais
借助高分辨率的三维直接数值模拟，我们研究了在时间增长的混合层中出现的纵向涡丝的起源和拓扑结构。基本速度场是双曲正切剖面U tanh（2 y/δi），雷诺数Uδi/v =100。计算使用伪光谱方法，并在包含四个基本最放大波长（L=4λa）的尺寸为L的立方体中以1283个网格点的分辨率进行。初速度场是基本速度，在其上叠加了一个宽谱的三维高斯扰动，峰值在ka=1/2πλa，动能等于10− 4 U 2，在横向上由高斯exp[−（y/δi）2]调制。还求解了一个被动标量输运方程，其初始分布与基本速度分布相同。被动标量和三个涡量分量的等值面被可视化，允许流动的三维涡结构。
We investigate, with the aid of a three‐dimensional direct‐numerical simulation at high resolution, the origin and topology of the longitudinal vortex filaments which appear in the temporally growing mixing layer. The basic velocity field is a hyperbolic‐tangent profile U tanh(2y/δi), with a Reynolds number of Uδi/ν =100. The calculation uses pseudospectral methods, and is carried out at a resolution of 1283 grid points in a cubic box of size L containing four fundamental most‐amplified wavelengths (L=4λa). The initial velocity field is the basic velocity, upon which is superposed a three‐dimensional Gaussian perturbation of wide spectrum, peaking at ka=1/2πλa, with kinetic energy equal to 10−4U2, modulated by a Gaussian exp[−(y/δi)2] in the transverse direction. A passive‐scalar transport equation is solved as well, with the same initial profile as the basic velocity profile. Isosurfaces of the passive scalar and three vorticity components are visualized, permitting the 3‐D vortex structure of the flows ...