Scaling Parameters for a Time-Averaged Separation Bubble

Abstract

A splitter plate is placed in the wake of a two-dimensional bluff body. The splitter plate is long enough for the separated flow behind the body to reattach on the splitter plate. The time-averaged properties of this “closed” separation bubble are investigated under a wide range of kinematic conditions. It is found that blockage reduces the base pressure coefficient (Cpb ) and the distance to reattachment (l) but the relationship between l and Cpb is not obvious. The pressure distribution in the separated zone, scaled on Cpb and l, can be described by a universal curve. The usefulness of a slotted wall in reducing blockage effects on bluff body flows is shown to be limited in that the wall porosity affects only some properties of the separation bubble.