Hydrodynamic noise and surface compliance--an overview of the Naval Underwater Systems Center IR/IED program

This Independent Research and exploratory development program on compliant surfaces is investigating turbulent flows over compliant layers to determine whether a class or classes of such layers can be devised for control and reduction of hydrodynamic (flow) noise. To accomplish this end we are addressing the coupled fluid/elastic problem to characterize the flow/layer interactions, resultant effects on the turbulent velocity components and effects both at the surface and within the layer. The motivation for the NUSC program is provided by an experiment in 1960 in which significant reductions in the turbulent boundary layer wall pressure spectra were measured on a vehicle coated with U.S. rubber Lamiflo. The Lamiflo coating was basically a version of a dolphin-like surface devised to extend Kramer's well known drag reductions investigations into the flow noise domain. The measured flow noise reductions have yet to be adequately explained or understood. The NUSC program seeks to develop an adequate physical framework within which the effects of compliant layers on flow noise may be understood.