Experimental study of pressure fluctuations and flow perturbations in air flow through vibrating pipes

This paper discusses the results of an experimental study of the effect of pipe oscillations on the wall pressure field and flow rate through a metallic pipe with air flowing through it. The data presented in this paper show that the frequencies of pressure oscillations in a non-oscillating pipe are identical to the natural structural modes of the pipe suggesting the influence of structural properties on the fluid dynamics of the flow. The results presented in this paper also show that the wall pressure undergoes both a temporal as well as a spatial oscillation if the pipe is forced to oscillate periodically. The pressure oscillations are found to be harmonics of the pipe oscillations. There is a drop in the mean pressure when the pipe is subjected to periodic oscillations. The flow rate through the pipe is seen to undergo a periodic change over a range of almost 7 percent variation when the pipe is oscillated. The study presented in this paper elucidates the dominant effect of system dynamics on determining the flow behavior through a rigid pipe. The adverse effect of flow oscillations, induced by pipe motion, can lead to departure of the flow from the intended design conditions and can render the fluid supply system inadequate.