Short-time evolution of Lagrangian velocity gradient correlations in isotropic turbulence
Short-time evolution of Lagrangian velocity gradient correlations in isotropic turbulence
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DOI：
10.1063/1.4936140
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发表时间：
2015-11
影响因子：
4.6
通讯作者：
L. Fang;W. Bos;G. Jin
中科院分区：
文献类型：
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作者：
L. Fang;W. Bos;G. Jin
通过直接数值模拟（DNS），我们发现均匀各向同性湍流中速度梯度的拉格朗日互相关在短时间内增加，而其自相关性降低。运动学的考虑允许表明，两个不变量的湍流速度场确定的短时间的速度梯度的相关性。为了更直观地了解更长时间的动力学，提出了涉及局部剪切和旋转的组合作用的启发式模型。这些模型定量地再现了这些影响，并理清了导致DNS中观察结果的不同物理机制。
We show by direct numerical simulation (DNS) that the Lagrangian cross correlation of velocity gradients in homogeneous isotropic turbulence increases at short times, whereas its auto-correlation decreases. Kinematic considerations allow to show that two invariants of the turbulent velocity field determine the short-time velocity gradient correlations. In order to get a more intuitive understanding of the dynamics for longer times, heuristic models are proposed involving the combined action of local shear and rotation. These models quantitatively reproduce the effects and disentangle the different physical mechanisms leading to the observations in the DNS.