Experimental Study of Wall Pressure Fluctuations in a Pipe behind a Stenosis

Abstract

Wall pressure fluctuations in a pipe, pt, behind a stenotic narrowing are studied. Sharp increase of the pressure pt in a finite region immediately downstream of the stenosis and the presence of a pronounced pressure maximum upstream of the point of re-attachment of the separated flow are found. Approximate estimates both for the distance from a stenosis to the point of maximum pressure and the pressure magnitude at this point are obtained. The study of the wall pressure power spectrum, P(ω), reveals low-frequency maxima in it. They are determined by the appropriate large-scale eddies in the regions of separated and re-attached flow, and their frequencies are close to the characteristic frequencies of the eddies' formation. These maxima are the main distinguishing features of the spectrum under investigation compared to the power spectrum of the wall pressure fluctuations in a fully-developed turbulent pipe flow.