Experimental characterization of turbulent subsonic transitional–open cavity flow

Turbulent subsonic “transitional–open” cavity flow was investigated by wind-tunnel tests. The investigated cavity configuration had a length-to-depth ratio of 6.25 and a width-to-depth ratio of 2. The cavity was exposed to a free-stream Mach number of 0.40 and a Reynolds number (based on cavity depth) of \(1.6\times 10^6\), with a turbulent incoming boundary layer. Measurements of velocity and wall pressures were taken simultaneously, which enabled the analysis of velocity–pressure cross-correlations. Special attention is paid to the shear layer that develops over the cavity and an emphasis is placed on the analysis of its characteristics and its stability. Application of linear hydrodynamic stability theory, together with examining velocity–pressure cross correlations, revealed that the behavior of the cavity shear layer is analogous to a free shear layer, approximately up to mid-length of the cavity, where further downstream nonlinear interactions occur.