1921 音波による長方形噴流の制御(S21-4 噴流,後流及びはく離流れの流動解析と応用(4),21世紀地球環境革命の機械工学:人・マイクロナノ・エネルギー・環境)

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Effect of acoustic excitation on rectangular jet characteristics, such as spreading, stretching and flapping, is discussed in this study. Sound wave locally irradiated the jet at a nozzle exit enables 'phase-lock' which means synchronization between flow oscillation and external sound. Therefore, hot-wire measurement by means of phase locking directly provides a phase averaged flow field. We especially focused on the effect of excitation modes, amplitude and frequency on jet characteristics. As a result, the jet flapping motion became strongly apparent for asymmetric excitation mode with large amplitude excitation. Then the jet spreading and shrinking in the major and minor plane occurred rapidly. In other words, the axis switching position moved upstream for this excitation condition. In contrast, for the symmetric excitation mode, jet pulsating motion was clearly observed, and there was no change in the jet spread rate. The enhancement of periodic-velocity fluctuation and non-periodic velocity fluctuation was completely different between both excitation modes.
2008-08-02