Rectangular and modified two-dimensional cavities in an open-jet anechoic wind tunnel at low mach number

Abstract

Experimental investigations are presented of noise from flow over unmodified and modified two-dimensional cavities at low Mach number, using an open-jet anechoic wind tunnel facility. The Reynolds numbers based on cavity depth were Re D=4100- 16500. Four cavity lengths were tested, which gave length-todepth (L/D) ratios of 1.17, 2.33, 3.5 and 4.67. There was a thin laminar boundary layer upstream of the cavity. The cavity was modified using sloped walls, a passive control technique for cavity flow noise. Such modifications were found to, typically, reduce overall sound pressure levels and to reduce the number or intensity of acoustic tones.