Regions with shearing motions are investigated in isotropic turbulence with the triple decomposition, by which a velocity gradient tensor is decomposed into three components representing an irrotational straining motion, a rotating motion, and a shearing motion. A mean flow around the shearing motions shows that a thin shear layer is sustained by a biaxial strain, which is consistent with Burgers' vortex layer. The thickness of each shear layer is well predicted by Burgers' vortex layer. A comparison between genuine turbulence and a random velocity field confirms that the biaxial strain acting on the shear is a dynamical consequence from the Navier-Stokes equations rather than from a kinematic relation. The interplay between the shear and biaxial strain causes enstrophy production and strain self-amplification. For a wide range of Reynolds number, the shear is strong enough for the instability to cause a roll-up of the shear layer, where the perturbation grows much faster than large-scale turbulent motions.

中文翻译：

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不可压缩各向同性湍流中的剪切运动特征

研究了在三向分解的各向同性湍流中具有剪切运动的区域，通过该区域，速度梯度张量被分解为三个分量，分别代表非旋转应变运动，旋转运动和剪切运动。剪切运动周围的平均流量表明，薄的剪切层受到双轴应变的维持，这与伯格斯的涡旋层一致。每个剪切层的厚度可以通过伯格斯的涡旋层很好地预测。真实湍流和随机速度场之间的比较证实，作用在剪切面上的双轴应变是来自Navier-Stokes方程的动力学结果，而不是运动学关系。剪切应变与双轴应变之间的相互作用会导致回旋产生和应变自增。