Abstract
Experiments on vortex shedding within a choked duct and its coupling with the duct’s longitudinal acoustic modes are reported. The vortex shedding and impingement mechanism was produced by a pair of concentric orifice plates placed within the duct. The results of the experiments demonstrate that the frequencies and strengths of the measured acoustic tones depend on the flow velocity, Reynolds number, orifice size, and orifice spacing. A standing wave was produced when the orifice-pair tone was near a longitudinal acoustic mode of the chamber. The oscillation frequency increased slightly with increasing Reynolds number but usually remained within 2-3% of a chamber longitudinal mode. Dual tones and abrupt frequency shifts in singular tones were observed for changes in Reynolds number and/or plate-to-plate spacing. The results of these experiments are part of an ongoing study to better understand the fundamental mechanisms of vortex-induced pressure oscillations within a flow chamber.
