Experimental investigation into the mechanism of discrete frequency noise generation from a flat plate immersed in a uniform oncoming flow

The mechanism of discrete frequency noise generation from a flat plate having a sharp trailing edge, which is immersed in a uniform oncoming flow, was investigated experimentally by the intensive measurements of the flow properties near the plate. As a result, it was made clear that the necessary conditions for the generation of discrete frequency noise are (1) that there is a dead flow region with a definite area and (2) that the shear flow starting from the separation points near the trailing edge is very strong on either or both sides of the plate. These conditions are easily satisfied by the existence of a laminar boundary layer on the surface. So, the mechanism is identical with the discrete frequency noise generated by the Karman vortex shedding from a blunt body immersed in a flow.