Acoustic diffraction by a half-plane with discontinuous boundary conditions

A theoretical investigation of the wake pattern downstream of airfoils under predominantly laminar flow conditions and the resultant noise generation is presented. Under these conditions the wake is dominated by a Karman vortex street. A method is developed to theoretically predict the vortex shedding frequency by relating the wake pattern to the airfoil boundary layer parameters through the momentum equation. The generated noise is found to be dominated by a pure tone at the vortex shedding frequency. The results obtained with the present approach were found to agree quite well with experimental results obtained by other investigators.