Statistical properties of an incompressible passive vector convected by isotropic turbulence
Statistical properties of an incompressible passive vector convected by isotropic turbulence
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DOI：
10.1103/physrevfluids.4.064601
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发表时间：
2019-06-03
影响因子：
2.7
通讯作者：
Watanabe, Takeshi
中科院分区：
文献类型：
--
作者：
Yang, Jingyuan;Gotoh, Toshiyuki;Watanabe, Takeshi
通过与速度和被动标量的比较，研究了均匀各向同性湍流对流作用下不可压被动矢量的统计特性，探讨了速度矢量和被动标量统计特性异同背后的物理机制。被动矢量遵循类似于Navier-Stokes方程的方程，具有伪压力以确保矢量的不可压缩性。导出了被动矢量的vonKarman-Howarth方程，在惯性对流范围内，速度增量乘以被动矢量增量的平方的平均值服从4/3定律。我们进行了多达1024（3）个网格点的直接数值模拟（DNS）。动、拟动能谱和标量方差服从k（-5/3）幂律。速度的柯尔莫哥洛夫常数为C-K = 1.57，被动矢量的柯尔莫哥洛夫常数为C-K（w）= 0.99，被动标量的奥布霍夫-科尔森常数为C-OC = 0.67。被动矢量的补偿谱的谱凸略大于速度的谱凸，但小于被动标量的谱凸。研究发现，由于赝压力的非局域效应，大尺度下的被动矢量涨落行为与速度的行为接近，而小尺度下的涨落行为与被动标量的行为相似。对流项的非线性是小尺度下速度场和被动场之间差异的关键。
Statistical properties of an incompressible passive vector convected by homogeneous isotropic turbulence are studied by comparing to the velocity and passive scalar, in order to explore the physics behind the differences and similarities in the statistical properties between the velocity vector and passive scalar. The passive vector obeys an equation similar to the Navier-Stokes equation, with a pseudopressure to ensure the incompressibility of the vector. The von Karman-Howarth equation for the passive vector is derived and the average of the velocity increment times the square of the passive vector increments obeys a 4/3 law in the inertial-convective range. We carried out direct numerical simulations (DNSs) of up to 1024(3) grid points. The spectra of the kinetic and pseudokinetic energies and the scalar variance obey a k(-5/3) power law. The Kolmogorov constants are C-K = 1.57 for the velocity and C-K(w) = 0.99 for the passive vector, and the Obukhov-Corrsin constant of the passive scalar is C-OC = 0.67. The spectral bump of the compensated spectrum of the passive vector is slightly larger than that of the velocity, but smaller than the passive scalar. It is found that the behavior of the passive vector fluctuations at large scales is close to that of the velocity due to the nonlocal effects of the pseudo-pressure, while the small-scale fluctuations resemble those of the passive scalar. The nonlinearity of the convective term is key to the differences between the velocity and passive fields at small scales.