周期変動噴流を用いた後方ステップ流れの能動的制御 : 第1報,噴流条件の影響とはく離流れ場の構造(流体工学,流体機械)

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Backward-facing step flows with horizontal or vertical synthetic jets fed from the vicinity of the step edge have been investigated to clarify effects of the synthetic jets on separated-reattachment flows as well as to obtain new knowledge for the active control of the flows. Relations between reattachment length and flow control parameters, such as frequencies and velocities of the jet, have been studied. Then details of the flow fields have been obtained with time-mean as well as phase-locked average procedures. Changes in the reattachment length for constant non-dimensional jet velocity are mostly determined from a ratio of the jet frequency to natural frequency of velocity fluctuation without a jet. The reattachment length becomes a minimum when the jet frequency ratio is around unity and decreases in proportion to the non-dimensional jet velocity to the power of -0.11〜-0.13. The feed of the synthetic jet makes shear layers in the downstream of the step edge be periodical organized vortices which induce organized periodic velocity fluctuation and causes non-organized random fluctuations with lower frequencies. These velocity fluctuations stimulate mixing of the fluids in the main stream and in the reverse flow region to promote the flow reattachment.
社団法人日本機械学会の論文
2009-01-25