Abstract

It has been shown experimentally that an adverse pressure gradient leads to periodic deceleration of the boundary layer of a plane-parallel flow in an open channel. During the deceleration, the action of the reverse pressure gradient and friction force forms an instantaneous vertical velocity profile with a local minimum above the viscous layer between two inflection points. In a thin layer containing the upper inflection point, the plane-parallel flow is unstable, which has been confirmed experimentally: a cylindrical vortex is formed in this layer at a critical value of the reverse pressure gradient when the deceleration cycle terminates.

中文翻译：

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具有不利压力梯度的流动减速过程中垂直速度剖面的变形

摘要

实验表明，不利的压力梯度会导致明渠中平面平行流的边界层周期性减速。在减速过程中，反向压力梯度和摩擦力的作用在两个拐点之间的粘性层上方形成具有局部最小值的瞬时垂直速度剖面。在包含上部拐点的薄层中，平面平行流动是不稳定的，这已被实验证实：当减速循环终止时，在反向压力梯度的临界值处，在该层中形成圆柱涡旋。