1993 Fiscal Year Final Research Report Summary
Mechanism of Bubble Generation and Dynamics of Laser-Induced Bubbles in Liquid Nitrogen
| Project/Area Number |
04452137
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
Fluid engineering
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| Research Institution | Tohoku University |
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Principal Investigator |
SHIMA Akira Institute of Fluid Science, Tohoku University ; Professor, 流体科学研究所, 教授 (30006168)
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| Co-Investigator(Kenkyū-buntansha) |
TOMITA Yukio Faculty of Education, Hokkaido University of Education ; Associate Professor, 教育学部函館校, 助教授 (00006199)
TUBOTA Makoto Institute of Fluid Science, Tohoku University ; Associate Professor, 流体科学研究所, 助教授 (10197759)
TAKAYAMA Kazuyoshi Institute of Fluid Science, Tohoku University ; Professor, 流体科学研究所, 教授 (40006193)
KOBAYASHI Ryouji Faculty of Engineering, Tohoku University l Professor, 工学部, 教授 (70006170)
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| Project Period (FY) |
1992 – 1993
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| Keywords | Bubble / Cavitation / Liquid Nitrogen / Low Temperature / Cryostat / Pulsed Laser / Phase Change / Interface Instability |
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| Research Abstract |
A single bubble was generated by focusing a pulsed ruby laser into liquid nitrogen at around boiling point under atomospheric pressure. We succeed in producing a highly spherical buble by means of an annular laser beam adjusted from a double-stage lens array. We obtained the relation between laser energy and induced bubble size for various surrounding pressures. As a result, it is found that the energy required for the bubble creation is exceedingly large compared with that estimated by assuming quasi-static phase change. It is also suggested that the plasma production is significantly related to the bubble generation. On the other hands, very weak pressure dependency is found for the threshold of bubble creation within the limit of the present experiment. The laser-induced bubble motion is optically observed using a high speed camera. It is crearly seen that during the growth process the bubble motion is primarily affected by the liquid inertia, but in the collapse phase heat transfer is dominant an resulting in the retardation of the bubble motion. A bubble contracts attainable to the minimum radius of about 40% of the maximum radius. Subsequently it rebounds, yielding a shock wave propagating outwards. Furthermore a notable instability takes place on the bubble surface immediately after the bubble rebound, causing highly disturbed surface, which is kind of a similar phenomenon observed in the case where a bubble behaves in water at around the saturation state. This kind of instability seems to be resulted from the Taylor instability coupled with the thermal one. By introducing a thermodynamic parameter, the effects of thermal and liquid inertia are evaluated associated with the motion of bubbles in both liquids, liquid nitrogen and water. The majority if the results obtained here are scheduled to be presented at the 2nd international symposium on cavitation to be held in Tokyo, April 5-7, 1994.
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