Strouhal numbers of flow-excited acoustic resonance of closed side branches

Flow-excited acoustic resonances of piping systems containing closed side-b ranches are often encountered in engineering applications. They are excited by the unstable shear layer which separates the mean flow in the main pipe from the stagnant fluid in the branch. The object of this paper is to deve lop a design chart that can be used to predict the critical flow velocities in the main pipe at which acoustic resonances are initiated. Model tests w ere carried out on three different configurations of side-branches (single, tandem, and coaxial branches). For each of these pipe configurations, the effects of the diameter ratio, the distance from an upstream elbow and the acoustic damping are investigated in some detail. The test results are impl emented into a design chart to predict the flow velocity at the onset of re sonance as a function of the system operational and geometric parameters. ( C) 1999 Academic Press.