Three-dimensional vortical structure in lid-driven square cavity flows.

Abstract

A three-dimensional vortical structure of a lid-driven square cavity flow was studied by flow-visualization techniques. Several sectional patterns of the flow visualized by a thin laser sheet showed that the structure was characterized by cells periodically aligned in the spanwise direction of the cavity. The cell consisted of both a pair of two vortex rings whose sense of rotation was opposite each other and a pair of two U-shape secondary vortices at corners. The vortex rings were a part of a primary vortex, and similar to the Taylor vortices between two coaxially rotating cylinders. The cells fluctuated in the spanwise direction with a long period of time 56H/U0, U0 being the velocity of the lid. A time-mean interval of the cells was found as a function of Reynolds number which was defined in terms of velocity U0 and the height H of the cavity in a range from 500 to 3000. The time-mean interval was independent of the aspect ratio A of the cavity, if A was greater than or equal to 3.