Experimental study on vortex sound interaction of acoustic resonance and its suppression in a flow duct

Abstract

Acoustic resonance induced by vortex shedding in flow passages is widely detected in various of engineering applications such as aeroengine compressors, tubular heat exchangers and so forth. The coupling between vortex and sound is still an open issue. Experimental results of vortex sound interaction in acoustic resonance induced by vortex shedding from bluff bodies in a flow duct are presented in this paper, with special attention being paid to the suppression strategy using acoustic treatment on the duct wall. Two sets of experiments, including hard wall condition and non-locally reacting liner condition, are conducted in a low-speed wind tunnel. The “dominant region” and “synchronous region” are observed in both the lock-in region of sound wave and vortex shedding signal. The frequency of the acoustic β-mode of the test section is different from the dominant frequency of the dominant region and the locked frequency of the synchronous region. And acoustic feedback plays an important role in it. The acoustic liner can effectively suppress the process of acoustic feedback. When one side of the duct wall is replaced by a non-locally reacting liner with a sound absorption coefficient of approximately 0.4, the lock-in region disappears and the resonant amplitude of sound pressure and the corresponding fluctuation velocity are greatly reduced, which indicates a convenient strategy for acoustic resonant suppression.