Visual Observation of the Vortex Structure in a Step Flow Induced by Uniform Flow

Abstract

Coherent structure in the neighbourhood of reattachment point by the step flow was investigated using the technique of flow visualization. For the simultaneous visualization of the streamwise view and the spanwise view, the methods using fluorescent dye illuminated by laser light sheets. It has developed that the streamwise vortex is appeared in the upper layer of the spanwise vortex, and that the streamwise vortex is caused by the occurrence of the horseshoe vortex. Further, it was observed that the length of the separated region is about seven times of the step height, and that the reattachment point is fairly fluctuated in correspondence with the move of spanwise vortex.