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International Journal of Aerospace Engineering
Volume 2016, Article ID 7347106, 16 pages
Research Article

Effects of Freestream Turbulence on Cavity Tone and Sound Source

Department of Mechanical Engineering, Toyohashi University of Technology, 1-1 Hibarigaoka, Tempaku, Aichi 441-8580, Japan

Received 6 July 2016; Accepted 10 November 2016

Academic Editor: William W. Liou

Copyright © 2016 Hiroshi Yokoyama et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


To clarify the effects of freestream turbulence on cavity tones, flow and acoustic fields were directly predicted for cavity flows with various intensities of freestream turbulence. The freestream Mach number was 0.09 and the Reynolds number based on the cavity length was 4.0 × 104. The depth-to-length ratio of the cavity, , was 0.5 and 2.5, where the acoustic resonance of a depth-mode occurs for = 2.5. The incoming boundary layer was laminar. The results for the intensity of freestream turbulence of Tu = 2.3% revealed that the reduced level of cavity tones in a cavity flow with acoustic resonance was greater than that without acoustic resonance . To clarify the reason for this, the sound source based on Lighthill’s acoustic analogy was computed, and the contributions of the intensity and spanwise coherence of the sound source to the reduction of the cavity tone were estimated. As a result, the effects of the reduction of spanwise coherence on the cavity tone were greater in the cavity flow with acoustic resonance than in that without resonance, while the effects of the intensity were comparable for both flows.