Abstract: A wave generation device includes a main flow channel and one or more side channels to initiate vortex shedding and generate a resonant free-surface standing wave. The main channel is a duct for the passage of a fluid such as water. The side channel or channels can be perpendicular or parallel to the main channel. Operation of the wave generation device relies on the exchange of energy between the unsteady vorticity-bearing flow in the main channel across the opening of the side channel cavity and the velocity field due to the resonant standing wave that forms in said cavity. The incoming flow of the main channel causes a cross-flow fluctuation in the separating shear layer as it is disturbed at the leading corner of the side channel, which is amplified in the streamwise direction. This fluctuation resonates within the side channels, generating the standing wave.