有壁流动中的Angular momentum平衡和涡流产生
Angular momentum balance and vortex production in wall-bounded flows
摘要：
为了产生涡流，必须对流体施加扭矩。在粘性流体中，一旦粘性摩擦力超过流体的剪切应力阻力，则产生湍流涡旋的扭矩是由于应力张量的对称性丧失所致。特别是在有壁面的流动中，湍流涡流形成于靠近壁面的流体薄层中，实际上与所谓的粘性子层重合，在粘性子层中粘性摩擦力达到最大值。本文确定了该子层的涡结构，与该区域的平均流向速度图的众所周知的线性一致。分析使我们能够计算的直径，角速度，并在稳态条件下的粘性子层中的旋涡的轴间。确定了使涡从壁面向主流迁移的升力，并讨论了陀螺进动在涡轴重定向中所起的关键作用。
英文摘要：
To produce a vortex, a torque must be applied to the fluid. In viscous fluids, the torques that produce turbulent vortices result from the loss of symmetry of the stress tensor, once the viscous friction exceeds the shear stress resistance of the fluid. In wall-bounded flows, in particular, the turbulent vortices form in a thin layer of fluid adjacent to the wall, practically coinciding with the so-called viscous sublayer, where the viscous friction reaches the largest values. The present paper determines a vortex structure for this sublayer, consistent with the well-known linearity of the diagram of the mean streamwise velocity of this region. The analysis enables us to calculate the diameter, angular velocity, and interaxis of the vortices in the viscous sublayer in steady-state conditions. The lifting force that makes the vortices migrate from the wall towards the mainstream flow is determined, and the crucial role played by gyroscopic precession in the reorientation of the vortex axis is discussed.
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