The effect of the backing cavity on the control of the turbulent boundary layer by the application of a cavity array

Abstract

The streamwise velocity fluctuations within a fully developed turbulent boundary layer has been investigated downstream of a flushed-surface cavity array underneath a flat plate. The size of the holes in the cavity array were selected to be comparable with the dimensions of the expected coherent structures, based on the friction velocity. This study investigates the effect of the backing cavity volume on attenuation of turbulent energy production within the logarithmic region of the turbulent boundary layer. To this end the turbulence intensity profile and sweep attenuation for three different backing cavity volume have been investigated. All measurements were taken in a closed-loop low turbulence wind tunnel at two different free stream velocities. The results show that when the backing cavity’s volume is equal to V+=3×103 the turbulence intensity and sweep intensity are reduced by up to 8% and 7.2% respectively. From this investigation it has been shown that the dampening of sweep events is not solely due to the walls of each individual cavity.