The investigation concerned noise produced by turbulent flow adjacent to a flexible wall.Measurements of the spectrum and intensity of the pressure field outside thin-walled Mylar cylinders containing turbulent pipe flow have been made.The resulting spectra could be interpreted in relation to the elastic properties of the cylinders and the character of the turbulent fluctuations inside the flow. The eigen frequencies of the cylinders could be identified and similarity parameters for the spectra were established.The effect of cylinder wall thickness on the spectrum and intensity of the pressure fluctuations was investigated.It was found that the intensity of the external pressure field scaled with the fifth power of the velocity at the center of the pipe.
For one particular case the spectrum and intensity of the pressure fluctuations exerted by the turbulent flow on the wall were measured.The intensity of the pressure fluctuations at the wall scaled with the fourth power of the velocity as expected.The ratio of the root-mean-square wall pressure to the dynamic pressure was found to be independent of Mach number and equal to a constant (0.0078).Similarity laws for the spectra of the wall pressure fluctuations were also confirmed.
