Wake flow-induced acoustic resonance around a long flat plate in a duct
- 87 Downloads
Flows around long thin blunt flat plates generate acoustic resonances when the sound frequency generated by the vortex shedding becomes close to the frequency of the acoustic mode around the plate. After their mutual capturing, the sound intensity strongly increases. To better understand this phenomenon, here we investigate the interaction between flow and flow-induced acoustic resonance around a long flat plate in a duct. Three acoustic resonance modes were observed as the flow velocity was increased. The acoustic resonance behavior is studied as a function of the shapes of the leading and trailing edges (semicircular and square) and the length of the plate (39 ≤ L/d ≤ 71). The Reynolds numbers based on the plate thickness and free-stream flow velocity ranged from 3300 to 21,300. The influence of the leading edge separation bubble and the trailing edge wake flow on the acoustic resonance is scrutinized by examining the velocity profiles, power spectra, and pressure sound level. The nonlinear behavior of the flow components in the wake is shown at monochromatic sound in the resonance regime. The difference in flow conditions around the plate for the diverse shapes of leading and trailing edges leads to the different efficiency of the sound-flow interaction, which originates the different sound level. It was found that the configuration with a semicircular leading edge and a semicircular trailing edge is the best one for generating aeroacoustic resonance. Possible physical explanations are proposed.
KeywordsVortex Resonance Mode Separation Bubble Engineer THERMOPHYSICS Acoustic Resonance
Unable to display preview. Download preview PDF.
- 2.Bardakhanov, S.P. and Kozlov, V.V., Control of Instability Waves Development in Separated Swirling Flows, Proc. Royal Aeronautical Soc. Conf. on High Lift and Separation Control, London, 1995, 30.1–30.14.Google Scholar
- 3.Bardakhanov, S.P. and Lygdenov, V.T., Coherent Structures in Wake behind Bluff Body and Generation of Sound in Resonance Conditions, Izv. SO AN SSSR, Ser. Techn. Nauk, 1990, vol. 2, pp. 36–40.Google Scholar
- 4.Bardakhanov, S.P. and Poroshin, E.V., Study of Aeroacoustic Resonance Features in Flow with Coherent Structures, Thermophys. Aeromech., 1994, vol. 1, no. 4, pp. 313–322.Google Scholar
- 8.Hirschberg, A., Bruggeman, J.C., Wijnands, A.P.J., and Smits, N., The “Whistler Nozzle” and Horn as Aero-Acoustic Sound Sources in Pipe Systems, Acustica, 1989, vol. 68, pp. 157–160.Google Scholar
- 19.Sukhinin, S.V. and Bardakhanov, S.P., Aeolian Tones of a Plane in a Duct, J.Appl. Mech. Tech. Phys., 1998, vol. 39, no. 2, pp. 68–76.Google Scholar
- 23.Yanenko, N.N., Bardakhanov, S.P., and Kozlov, V.V., Transformation of Acoustic Disturbances into the Vertical Ones at Turbulent Flows, in Nestabil’nost’ do- i sverkhzvukovykh potokov (Instability of Suband Supersonic Flows), Novosibirsk: ITAM, 1982, pp. 93–106.Google Scholar
- 24.Yanenko, N.N., Bardakhanov, S.P., and Kozlov, V.V., Transformation of Acoustic Oscillations into the Eddy Ones in Turbulent Flows, in Turbulence and Chaotic Phenomena in Fluids, North-Holland, 1984, pp. 427–432.Google Scholar