Hydrodynamic Interaction Between Whistling Axisymmetric Cavities in the Presence of a Coupling Longitudinal Standing Wave

An axisymmetric cavity along a pipe is a commonly encountered construction in industrial applications, which can also be considered as a unit element of a corrugated pipe. At critical conditions such a configuration causes severe noise problems, called whistling. Whistling is a self-sustained oscillation, driven by a flow-acoustic interaction. In the current study, the hydrodynamic interaction between two such cavities is addressed in the presence of a coupling standing wave along the pipe. The phenomenon is investigated both experimentally and numerically. The hydrodynamic interaction has a strong effect both for the amplitude and for the Strouhal number of the whistling, which depends critically on the separation distance between two adjacent cavities.