PRESSURE FLUCTUATIONS IN A SEPARATED FLOW REGION

This paper describes a preliminary experimental investigation of pressure fluctuations in a separated flow behind a thin fence. Methods of determining the position of recombination point, which is closely related to the position of maximum sound pressure level, are discussed. Noise sources within the flow are identified. Significant and parasitic variables are noted and a dimensional analysis is presented. A similarity relation is also presented, relating sound levels to frequencies and free stream velocities. Graphs of the variation of power spectral density with frequency, and sound level with distance behind the fence are given for distances up to 50 fence heights behind the fence. It has been found that the frequency spectra alter considerably with distance behind the fence and that the maximum sound level behind a fence is about eight times that in a turbulent boundary layer, with the same free stream dynamic head. © 1968, Acoustical Society of America. All rights reserved.