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Journal Articles

Evaluation growing and collapsing behaviors of cavitation bubbles under flowing condition

Kawamura, Shunsuke; Naoe, Takashi; Ikeda, Tsubasa*; Tanaka, Nobuatsu*; Futakawa, Masatoshi

Advanced Experimental Mechanics, 4, p.33 - 37, 2019/08

A mercury enclosure vessel made of stainless steel is used as a spallation target in the pulsed spallation neutron source at J-PARC. It is severely damaged by the cavitation induced with pressure waves in association with the pulsed proton beam injection. A double-walled structure with a narrow mercury channel was adopted in the front end of the target vessel to reduce the cavitation damage. It has been experimentally demonstrated that the cavitation damage could be mitigated in the narrow channel but its mechanism has been unclarified yet. In this study, we investigated the cavitation from growing to collapsing through visualizing the spark-induced cavitation bubbles under flow field using a high-speed video camera. Furthermore, we measured the wall vibration due to the cavitation bubble collapse with changing flow velocity parametrically. It was found that the microjet collided perpendicular to the wall in the stagnant flow condition while it collided with an inclined angle from the perpendicular direction, suggesting that the collision pressure on the wall was reduced by flowing.

Oral presentation

Visualization of cavitation growing and collapsing behaviors in narrow channel

Kawamura, Shunsuke; Naoe, Takashi; Ikeda, Tsubasa; Tanaka, Nobuatsu*; Futakawa, Masatoshi

no journal, , 

A mercury enclosure vessel made of stainless steel is used as a spallation target in the pulsed spallation neutron source at J-PARC. It is severely damaged by the cavitation induced with pressure waves in association with the pulsed proton beam injection. A double-walled structure with a narrow mercury channel was adopted in the front end of the target vessel to reduce the cavitation damage. It has been experimentally demonstrated that the cavitation damage could be mitigated in the narrow channel but its mechanism has been unclarified yet. In this study, we investigated the cavitation from growing to collapsing through visualizing the spark-induced cavitation bubbles under flow field using a high-speed video camera. Furthermore, we measured the wall vibration due to the cavitation bubble collapse with changing flow velocity parametrically. It was found that the microjet collided perpendicular to the wall in the stagnant flow condition while it collided with an inclined angle from the perpendicular direction, suggesting that the collision pressure on the wall was reduced by flowing.

Oral presentation

Flow effect on cavitation bubble behaviors in narrow channel

Kawamura, Shunsuke; Naoe, Takashi; Tanaka, Nobuatsu*; Futakawa, Masatoshi

no journal, , 

In the mercury target for the pulsed spallation neutron source at J-PARC, cavitation damage at the beam window of the mercury target vessel is a key factor to decide lifetime of target because the damage degrade the vessel structural integrity. A double-walled structure with a narrow channel was adopted to the vessel for expecting to reduce cavitation damage. In this study, the cavitation bubble behaviors of the growth and collapse under water flow field were investigated to determine the effective factor for mitigating cavitation damage in narrow channel. We measured the equivalent diameter and wall vibration due to the cavitation bubble collapse with parametrically changing flow velocity. It was found that the maximum equivalent diameter of the cavitation bubble and the response vibrational acceleration of the wall are decreased with the increasing velocity. As the results, it was found that cavitation bubble collapse pressure was affected by flowing condition in the narrow channel.

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