Acoustic radiation from pipes, excited by internal turbulent flow: Comparison of experimental results with theory

Abstract

The analysis of acoustic radiation from piping systems is complicated by the presence of multiple excitation sources; for example, mechanical valve vibration, acoustic near- and farfields, and the random pressure field of fully-developed turbulent flow will normally act together. This latter pressure field is well defined, and was chosen as the excitation for an initial parametric investigation of the response of and radiation from piping systems. An intermittent induced-flow pipe facility, mounted across an anechoic chamber, was used to obtain extensive measurements of the radiation from steel and P.V.C. pipes for a wide range of flow speeds and several pipe wall thicknesses. Theoretical predictions compare favourably with experimental measurements. The main conclusions are: the acoustic power radiation is resonant and well-described by considering only acoustically fast pipe vibration modes; this radiation is proportional to the modal loss factors and to the fifth power of flow Mach number. Comparisons between excitation by fully developed flow and propagating acoustic fields are given, which demonstrate their relative importance.