SUR LE TRANSFERT D'ÉNERGIE ENTRE UN ÉCOULEMENT TOURBILLONNAIRE ET UN CHAMP ACOUSTIQUE

Abstract
Experiments run either in a windtunnel or with the free surface hydraulic analogy have shown that, under certains conditions, strong coupling may occur between the vortex shedding of a cylindrical body placed upstream of the entrance of a cavity, and the acoustic waves propagating within the cavity. The strength of the coupling depends on several geometrical factors (cross section shape of cylindrical body, distance separating the cylindrical body from the cavity entrance, cavity depth) and on the flow velocity. These results may be explained on the basis of Howe's theory of aerodynamic sound which shows how energy is transferred from a fluid motion to an acoustic field or vice versa. Observation of the flow in the hydraulic analogy by shadowgraph technique and considerations based on Howe's theory have led to a modification of the cavity entrance to increase the energy transfer from the fluid motion to the acoustic field. Experiments carried out with this modification have fully confirmed the soundness of the theory.