Cavitation inception and the growth and collapse of bubble clouds in high-intensity focused ultrasound

2021 Fiscal Year Final Research Report

• Project/Area Number: 19H02070
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Basic Section 19010:Fluid engineering-related
• Research Institution: Osaka Prefecture University
• Principal Investigator: Takahira Hiroyuki 大阪府立大学, 工学(系)研究科(研究院), 教授 (80206870)
• Co-Investigator(Kenkyū-buntansha): 小笠原 紀行 大阪府立大学, 工学(系)研究科(研究院), 准教授 (00552184)
• Project Period (FY): 2019-04-01 – 2022-03-31
• Keywords: 混相流 / 気泡 / キャビテーション初生 / 集束超音波 / 後方散乱 / マルチスケール解析 / 準安定状態

Outline of Final Research Achievements

The cavitation inception due to the backscattering of high-intensity focused ultrasound (HIFU) from bubble interfaces in water and gelatin, leading to growth and collapse of bubble clouds, has been investigated experimentally. The dependency of the cavitation inception pressure on temperature has been revealed both experimentally and numerically. Also, the influence of bubble size as a reflector of HIFU on the bubble cloud formation has been investigated. A multiscale numerical simulation method which consists of the bubble dynamics in microscopic fields and the ghost fluid method and the level set method in macroscopic fields has also been developed for the growth of bubble nuclei and the bubble cloud formation in HIFU. The bubble cloud formation observed in experiments has been successfully simulated using the present method, which revels the mechanism of the bubble cloud formation.

Free Research Field

流体工学

Academic Significance and Societal Importance of the Research Achievements

極めて短い時間内に非常に局所的に強力な負圧を作用させる方法として，集束超音波(HIFU)のレーザ誘起気泡界面での後方散乱を利用して，キャビテーションを発生させる方法を確立した．本実験手法により，キャビテーション初生圧力の計測，ならびに，HIFU中での気泡クラウドの成長崩壊の解析が可能となった．また，気泡力学に基づき実験における気泡核の成長を理論的に予測する手法ならびに気泡核の成長モデルとGhost Fluid法を組み合わせたマルチスケール計算手法を開発した．本実験ならびに数値計算結果は，キャビテーション初生の予測に有用であり，キャビテーションを用いた医療応用に有用な知見を与えるものである．