SIMULATION OF THE RESONANT INTERACTIONS BETWEEN A BOUNDARY LAYER AND AN ARRAY OF DEEP CAVITIES

We have performed numerical simulations of the interaction between a laminar boundary layer flow and an array of deep slit-aperture cavities solving fully compressible Navier-Stockes equations with a finite-volume solver CharLESX . The cavities are included in the computational domain which allows to study the full interaction i.e. the excitation mechanism of the liner and its acoustic response. The parameter space is explored by varying the cavity depth D, thus shifting the cavity resonant modes fr,m = (2m− 1) c 4D , where m is a positive integer. Four cases, with varying cavity depth were studied. In all cases, the coupling of the grazing shear layer instabilities to the acoustic standing waves inside cavities (resonant interaction) leads to the generation of large Kelvin-Helmholtz (KH) rollers, scaling as λKH = Uc/ fr,1. In some cases, this coupling leads to the excitation of m > 1 resonant modes in the upstream cavities. However vortex merge occurring over the cavities switches the mode m = 1 further downstream. Overall, the results suggest that an array of deep cavities has a promising potential application for passive flow control.