VORTICES WITHIN THE SEPARATION IN A DECELERATING CHANNEL FLOW (PROFILES OF THE TIME-AVERAGED VELOCITY AND TURBULENCE LEVEL)

摘要

An experimental investigation was made into the three-dimensional separated flow and the vortices within the flow separation in a decelerating channel flow generated by the suction from a porous side wall. The flows along the side and bottom walls were visualized by the surface tuft method. And the turbulent internal flow was measured by the sprit-film probe to investigate the turbulent flow including the reverse flow. In the flow visualization for the strong decelerating flow (the suction flow ratio:0.8), two typical flow patterns appear alternatively. One is that the flow near the bottom wall separates more upstream than the flow near the top wall and a clockwise vortex can be seen in the separation region. Another is the reversal flow pattern with a counterclockwise vortex. By the turbulent flow measurement using the sprit-film probe, two peaks of turbulence level are observed for the strong decelerating flow case. These peaks can be related with two flow pattern mentioned above.