Noise generation in transonic tunnels

R emphasis has been placed on the noise environment in transonic facilities. This increased attention surrounding the tunnel noise problem was brought about by the advent of high lift configurations operating in the transonic regime. Experimental investigations' have shown that the tunnel noise environment may have a significant influence on high lift model boundary-layer transition and on the character and onset of buffet. Thus, an extensive analytical investigation of the noise generation mechanisms affecting the test section noise environment of porous wall transonic wind tunnels has been undertaken. The noise environment is broken up into three parts: 1) the noise attributable to the jet flow through the porous walls, 2) the noise produced by a wall hole-tunnel resonance phenomenon, and 3) the noise associated with the turbulent boundary layer on the test section walls and with the diffuser. With the formulation of the separate mechanisms, the contributions of each are added, forming a representation of the overall noise generation mechanism.