| Co-Investigator(Kenkyū-buntansha) |
SOYAMA Hitoshi Tohoku University, Institute of Fluid Science, Research Associate, 流体科学研究所, 助手 (90211995)
IKOHAGI Toshiaki Tohoku University, Institute of Fluid Science, Associate Professor, 流体科学研究所, 助教授 (90091652)
ESASHI Masanobu Tohoku University, Faculty of Engineering, Professor, 工学部, 教授 (20108468)
KATO Koji Tohoku University, Faculty of Engineering, Professor, 工学部, 教授 (50005443)
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| Research Abstract |
In order to make clear the flow characteristics and the dynamics in the ultra-highspeed micro-flow, we examined the cavitation characteristics of the ultra-highspeed flow. Then, we systematically observed the flow pattern in the nozzle and near the nozzle-outlet as well as the cavitating jet in a narrow watercourse, and also tried to simulate the cavitating flow numerically. The obtained results are summarized as follows :
1. We tested the ultra-pure water, whose resistance rate is more than 18 MOMEGA/cm. And, we made clear that the relative air content rates of the water, which is an important factor on the cavitation inception and develops, are considerably higher than that of tap-and still water. Then we made a special facility to degas the air within the ultra-pure water by using a special filtering membrane in order to avoid polluting the ultra-pure water, and we got the special ultra-pure water, whose relative air content rates are less than 0.2.
2. In order to make clear the flow
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pattern of ultra highspeed flow systematically, we carried out the observation and the erosion test on ultra highspeed water jets in the air and in the water. In the case of the jets in the water, it is shown that the jets are periodically shedding the cavitation bubble clouds. And also the erosion intensity is closely related to the cavitation bubble clouds.
3. The above-mentioned the erosion characteristics induced by the cavitation around the submerged highspeed water jets are systematically examined, the submerged water jets are very useful for cleaning and peening. Since the cavitation-impulse-pressures at the bubble collapsing can be effectively used on the cleaning and the peening, in the case of the submerged water jets. And also the suitable injection condition is shown for several nozzles.
4. In order to clarify the ultra highspeed flow pattern in a narrow watercourse, the cavitating jet in a narrow watercourse is carefully observed by means of a highspeed video camera, whose maximum framing rate is 40,500 frames per second and a digital image processing technique. The cavitation bubble clouds in the narrow watercourse are periodically shedding as same as the above-mentioned cavitation clouds associated with severely erosive cavitation. Less
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