Spectral Characteristics of the Pseudosonic Component of Hydrodynamical Noise In a Longitudinal Flow Around a Flexible Cylinder

Abstract

Wall pressure fluctuations were measured in an axisymmetric turbulent boundary layer on a flexible cylinder parallel to the flow at Reynolds numbers of 10 7 ‐10 8 and boundary layer thickness to cylinder radius ratio of 2:9 ‐3:2. It has been found out that the intensity of pressure fluctuations in the turbulent boundary layer on the flexible cylinder is higher than that on a rigid cylinder or on a flat plate. An adjusted power spectrum of the pressure fluctuations is presented. The acousto-hydrodynamic factor for the spot sensor of the pressure fluctuations has been determined. The power spectrum of the wall pressure fluctuations on the flexible cylinder has been found out to be higher than that on the rigid cylinder. With the increase of velocity of the flow around the flexible cylinder there occurs a redistribution of energy of the turbulent pressure fluctuations from the high frequency area of the power spectrum into lower frequencies. In the frequency band ! + ’ (0:2 ‐0:3) the maximums of the power spectrum and the coherence function irrespective of separation between the pressure fluctuation sensors are observed. With the increase of the frequency and separation, the coherence function descends, which characterizes a degeneracy of vortical structures both in scale and in the length of the cylinder in the flow.