Jiro Higuchi

Behavior of the Erosion-Standoff-Distance Curves for High-Speed Water-Jets in Air.

In order to clarify the mechanism of water-jet erosion, we systematically investigate the erosion-standoff-distance curves, the erosion-time curves, and detailed aspects of the eroded surface for two typical types of nozzles, i.e., conical and cylindrical nozzles. Clearly, the erosion-time curves are markedly different at the 1st peak, at the valley and at the 2nd peak. Hence, the mechanism of erosion is significantly changed with an increase in the standoff distance χ.

Discrimination of cavition stages through their probability-event-distributions.

キャビテーションの発達段階の判別を目途し,オリフィスに生ずるキャビテーションが発する衝撃音圧パルス列を介して,消滅,サブキャビテーションおよび遷移領域におけるパルス間の発生時間間隔の確率的統計挙動を調べた。その結果,各領域の確率分布には質的な差があり,それぞれ指数関数分布,正則分布および両者の中間的分布で表される。すなわち,発達段階の判別が質的な面から可能となった。

Stochastic behavior of subcavitation (With respect to .SIGMA.-dependence of shock-pressure-pulses).

To make clear the stochastic behavior of cavitation in near subcavitating range, we statistically analyzed the acoustic pressure pulses associated with the cavitation, and discussed the subcavitation by introducing the threshold level selected for the pulsedetection, for various states of test water as well as the behavior of several types of cavitation bubbles. The stochastic behavior is remarkably observed for a selected higher threshold level. After the bubble-cloud initiates, the pulse energy which directly relates to erosion, significantly deviates from the n-th power law of cavitation number σ, and rapidly decreases with σ.