Vortices Within the Flow Separation in a Decelerating Channel Flow: Time-Averaged Characteristics

An experimental equipment for studying the vortex behavior in 3D flow separation was constructed to have a comprehensive understanding of a separated channel flow. The separation occurs on three side walls of the straight channel by the suction from a porous side wall. Several types of separation can be generated by changing the sucked flow rate and providing the inlet flow with velocity gradient. For a strong decelerating-flow without the inlet velocity gradient, an alternate flow pattern with an opposite vortex occurs at considerably irregular intervals. With the inlet velocity gradient, a vortex appears and disappears along an inclined separation line for a moderate decelerating-flow, and a large stable vortex exists in the separation region for a strong decelerating-flow. The behavior of these vortices was examined and discussed in relation to the vortices including in the inlet flow.