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
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.