The effect of sound on vortex shedding from cylinders

Abstract

The influence of a transverse sound wave on vortex shedding from a rigid circular cylinder in a duct has been explored at Reynolds numbers from 20000 to 40000. In the absence of sound, the vortex shedding is found to consist of strings of coherent cyclic events which have frequencies that wander randomly about the nominal vortex-shedding frequency. Application of sound at the vortex-shedding frequency eliminates this wander and correlates the shedding along the cylinder axis. The frequency of vortex shedding can be shifted by sound applied either above or below the nominal vortex-shedding frequency. This entrainment is produced by the velocity induced by the sound wave rather than by the sound pressure. These phenomena are also observed in tube rows.

Suppression of three-dimensional flow instabilities in tube bundles

“…This may be due to the fact that significant transverse and streamwise vorticity (which is uncorrelated in the spanwise direction) is generated before the cylinder vibration is large enough to suppress the three-dimensional instability. This result does not agree with Blevins (1985)'s observation that acoustic forcing at the Strouhal frequency should correlate the flow in the spanwise directions, even at 20 000 ≤ Re ≤ 40 000. In this case the tight packing of the tube bundle may actually reduce the cylinder vibration amplitude compared to the single cylinder case considered by Blevins.…”

“…The in-phase cylinder vibration models the case of acoustic resonance, which was observed by Blevins (1985) to induce nearly perfect spanwise correlation of pressure for an isolated cylinder. We performed two-and three-dimensional simulations of fixed and free transverse vibrations of tube bundles at the relatively low Reynolds number Re = 200 (when only the mode A instability is present), and at the moderate Reynolds number Re = 1 000 (when the flow around the fixed cylinder is highly threedimensional and the three-dimensional instability is more complicated and much stronger).…”

“…For example, Price et al (1995) find that Strouhal frequency and rms drag do not change greatly with Reynolds number for Re > 150. Blevins (1985) demonstrated that acoustic forcing of an isolated cylinder at its Strouhal frequency is able to produce nearly perfect spanwise correlation of pressure for 20 000 ≤ Re ≤ 40 000. He conjectured that similar effects might be observed in tube bundles.…”

“…The natural frequency of the moving cylinders is tuned to match the Strouhal frequency in order to maximize the moving cylinder effect. All cylinders move in phase, which corresponds to the acoustic resonance conditions investigated by Blevins (1985).…”

Effect of Flow Induced Acoustic Resonance on Vortex Shedding from Staggered Tube Banks

“…On the other hand, some studies have been published on the effects of an acoustic wave on vortex shedding from a circular cylinder (17) - (20) . According to those papers, when loud sound was applied the frequency of vortex shedding locked at the frequency of the applied sound, the vortex shedding correlated with the sound and the amplitude of velocity fluctuation of vortex shedding increased.…”