Effect of pulsed slot suction on a turbulent boundary layer

Abstract

It is pointed out that even though slot suction has certain definite advantages over distributed suction, it has not attracted the detailed study that it merits. Measurements of mean velocity profiles, longitudinal turbulence intensities, and skin friction coefficients at a single downstream station are presented for various values of suction rate and frequency of pulsation. The data reveal that whereas suction (continuous or pulsed) does produce significant changes, especially in the mean velocity profile and turbulence intensity levels, these changes seem to depend only on the suction flow rate and not on the frequency of pulsing in the range of values covered in these experiments. As the suction flow rate is increased, the mean skin friction first drops to a minimum and then increases continuously, regardless of whether the suction is continuous or pulsed. It is concluded that unconditional pulsed control offers no special advantages at frequencies comparable to and below burst frequencies.