COUPLING OF VORTEX SHEDDING WITH THE FUNDAMENTAL RESONANT MODE OF A RESONATOR TUBE

An investigation of the coupling between the vortex shedding from a tr ip rod with triangular cross-section and a resonant mode of a tube is presented. The physical experiments were conducted using a shallow wat er channel; this system represents an hydraulic analogy of the acousti c resonator tube in airflow. The resonator tube differs from that used in previous physical experiments as a result of rounding the tips and increasing the size of the trip rod. Rounding the tips is found to re duce the level of vortex shedding from the tips. This increases the am plitude of the tube resonance as a result of lower damping of the osci llations. The spacing between the trip rod and the resonator tube lead ing to maximum resonance amplitude increases with increasing flow velo city. Numerical experiments using aeroacoustic theory to explain the t ransfer of energy between the resonance field and the mean flow field predict well this observed trend, as well as the source of wave energy .