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|標題:||Self-sustained oscillation induced by horizontal cover plate above cavity||作者:||Kuo, C.H.
|關鍵字:||shear-layer;flow oscillations||Project:||Journal of Fluids and Structures||期刊/報告no：:||Journal of Fluids and Structures, Volume 14, Issue 1, Page(s) 25-48.||摘要:||
When a horizontal cover plate is placed above a cavity, the mechanism leading to enhanced self-sustained oscillation within the cavity is investigated by experiment at a Reynolds number Re-theta o = 171 +/- 5. As the leading edge of the cover plate is located right above the most sensitive region of the cavity shear layer, the oscillating amplitude of shear layer instability is enhanced most effectively. However, this effectiveness decreases when the leading edge of the cover plate moves further downstream of the cavity. Three mechanisms are found to possibly modify the shear layer instability across the cavity. First of all, insertion of a horizontal cover plate above the cavity does impose a favourable streamwise pressure gradient that accelerates the flow across the cavity. This flow acceleration increases the amplification rate of shear layer instability. Second, the boundary layer characteristics (both the frequency band and the fluctuating amplitude) may also provide another opportunity to perturb the shear layer instability. Third, the shear layer is deflected into the cavity and leads to strong feedback. In the present study, all three mechanisms are equally important when the leading edge of the cover plate is positioned above the cavity mouth. However, when the leading edge of the cover plate is located downstream of the cavity, the first and the second effects diminish. In this situation, the stronger feedback due to the inward-deflected shear layer (the third effect) plays an important role to modify the shear layer instability. (C) 2000 Academic Press.
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