Self-sustained oscillations with acoustic feedback in flows over a backward-facing step with a small upstream step

DOI PDF 被引用文献9件
  • Hiroshi Yokoyama
    The University of Tokyo Graduate School of Engineering, , 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656 Japan
  • Yuichi Tsukamoto
    Hitachi Plant Technologies, Ltd. , 4-5-2 Higashi-Ikebukuro, Toshima-ku, Tokyo, 170-8466 Japan
  • Chisachi Kato
    The University of Tokyo Institute of Industrial Science, , 4-6-1 Komaba, Meguro-ku, Tokyo, 153-8505 Japan
  • Akiyoshi Iida
    Kogakuin University Faculty of Engineering, , 2665 Nakano-machi, Hachioji-shi, Tokyo, 192-0015 Japan

説明

<jats:p>Self-sustained oscillations with acoustic feedback take place in a flow over a two-dimensional two-step configuration: a small forward-backward facing step, which we hereafter call a bump, and a relatively large backward-facing step (backstep). These oscillations can radiate intense tonal sound and fatigue nearby components of industrial products. We clarify the mechanism of these oscillations by directly solving the compressible Navier-Stokes equations. The results show that vortices are shed from the leading edge of the bump and acoustic waves are radiated when these vortices pass the trailing edge of the backstep. The radiated compression waves shed new vortices by stretching the vortex formed by the flow separation at the leading edge of the bump, thereby forming a feedback loop. We propose a formula based on a detailed investigation of the phase relationship between the vortices and the acoustic waves for predicting the frequencies of the tonal sound. The frequencies predicted by this formula are in good agreement with those measured in the experiments we performed.</jats:p>

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