论文标题

从涡流传输的有效漂移速度

Effective Drift Velocity from Turbulent Transport by Vorticity

论文作者

Aluie, Hussein, Rai, Shikhar, Yin, Hao, Lees, Aarne, Zhao, Dongxiao, Griffes, Stephen M., Adcroft, Alistar, Shang, Jessica K.

论文摘要

我们强调了涡度和应变在长度大于$ \ ell $的长度(较小规模)湍流大于$ \ ell $上的粗粒量表中的转运中的不同作用。在粗粒(分辨)标量/动量的演变中出现的子量表通量/应力是(亚网格)尺度的效果小于粗粒度长度$ \ ell $。由于Eyink \ cite {eyink06a},我们在多尺度梯度扩展中使用了第一项,当分配长度$ \ ell $的任何比例都小于光谱峰的比例时,它与确切的子量表物理学表现出很高的相关性。我们表明,与量表菌株不同,它是各向异性扩散/抗扩散张量的,子量表涡度的贡献仅是通过涡流诱导的非发散速度($ \ bv _*$)对粗粒量的保守对象。因此,粗粒量的材料(Lagrangian)对流不是通过粗粒流速度($ \ ol \ bu_ \ ell $)来实现的,而是通过有效的速度,$ \ ol \ ol \ ol \ bu _ \ ell+el+\ el+\ bv _*$,其物理学可以改善常用的LES模型。

We highlight the differing roles of vorticity and strain in the transport of coarse-grained scalars at length-scales larger than $\ell$ by smaller scale (subscale) turbulence. %subscale flux/stress which appear in the evolution of coarse-grained (resolved) scalars/momentum account for the effect of (subgrid) scales smaller than the coarse-graining length $\ell$. We use the first term in a multiscale gradient expansion due to Eyink \cite{Eyink06a}, which exhibits excellent correlation with the exact subscale physics when the partitioning length $\ell$ is any scale smaller than that of the spectral peak. We show that unlike subscale strain, which acts as an anisotropic diffusion/anti-diffusion tensor, subscale vorticity's contribution is solely a conservative advection of coarse-grained quantities by an eddy-induced non-divergent velocity, $\bv_*$, that is proportional to the curl of vorticity. Therefore, material (Lagrangian) advection of coarse-grained quantities is accomplished not by the coarse-grained flow velocity, $\OL\bu_\ell$, but by the effective velocity, $\OL\bu_\ell+\bv_*$, the physics of which may improve commonly used LES models.

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