Experimental Investigation of Resonant Coupling Between Turbulent Flow Past a Rectangular Cavity and a Standing Gravity Wave

Coupling between self-excited oscillations of turbulent flow of water in an open channel along the opening of a rectangular cavity and the standing gravity wave in the cavity was investigated experimentally for a range of inflow velocities and characteristic depths of the water. The objective of the current investigation is to examine the effect of water depth on the onset of fully coupled oscillations of the shear flow past the cavity. Video recording of the oscillating free-surface inside the resonator cavity in conjunction with free-surface elevation measurements using a capacitive wave gauge provided representation of the resonant wave modes of the cavity as well as the degree of the flow-wave coupling in terms of the amplitude and the quality factor of the associated spectral peak. Moreover, application of digital particle image velocimetry (PIV) provided insight into the evolution of the vortical structures that formed across the cavity opening. Coherent oscillations were attainable for a wide range of water depths. Variation of the water depth affected the degree of coupling between the shear layer oscillations and the gravity wave as well as the three-dimensionality of the flow structure.