ASYMMETRIC RESPONSE OF TURBULENT CHANNEL FLOW TO WALL SUCTION AND BLOWING

A direct numerical simulation was performed to investigate the effects of spatially-varying wall suction and blowing on turbulent channel flow. Two combinations of wall suction and blowing were considered: one is a sequence of suction and blowing (S-B) and the other is a sequence of blowing and suction (B-S). A sinusoidal form of wall suction and blowing was applied at the lower wall of the channel through a spanwise slot, downstreeam of which the flow was allowed to adjust itself to a new boundary condition at the impermeable wall. The main emphasis was placed on the asymmetric response of wall-bounded turbulent flow to different sequencies of wall suction and blowing. The rate of adjustment and the relaxations after local actuations were evaluated. It was found that the time-mean velocity and Reynolds stresses were modified significantly depending on the sequences.