Formation and application of acoustic soliton with a high speed in water by utilizating an weakly nonlinear effect of cavitation

2023 Fiscal Year Final Research Report

• Project/Area Number: 18K03942
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 19010:Fluid engineering-related
• Research Institution: University of Tsukuba
• Principal Investigator: Kanagawa Tetsuya 筑波大学, システム情報系, 准教授 (80726307)
• Project Period (FY): 2018-04-01 – 2024-03-31
• Keywords: ソリトン / 衝撃波 / キャビテーション / 気泡 / 圧力波 / 非線形波動 / 混相流 / 気泡流

Outline of Final Research Achievements

In order to supress a damege of water pipe, we aimed a transition of shock waves in water into acoustic solitons. By utilizing a weak nonlinear effect of cavitation, the dispersion effect of waves caused by bubble oscillations appears, and when the nonlinear and dispersion effects are balanced, a soliton can be formed. On the other hand, when the nonlinear effect is balanced by the dissipation effect, a shock wave is formed. Therefore, quantitative evaluation of the three effects (i.e., nonlinear, dissipation, and dispersion effects) can lead to realization of the above idea. Focusing on the nonlinear wave equation as a mathematical model expressed as a linear combination f three terms representing these three effects, we developed various nonlinear wave equations including a fast propagation mode, and through quantitative evaluation of the three effects, we predicted the evolving waveform of pressure waves.

Free Research Field

流体工学

Academic Significance and Societal Importance of the Research Achievements

【学術的意義】非線形波動方程式の導出により得られた数理物理・応用数学的意義、非線形・散逸・分散の評価と発展波形予測（衝撃波・ソリトン等）による流体力学的意義、気泡流の平均化モデル方程式の構築による流体工学的意義などが挙げられ、多岐にわたる学術的知見を得られた。
【社会的意義】われわれの生活に欠かせない水管に対して、その損傷をソリトンにより回避しながらも、衝撃波の活用により洗浄を行うという新たな技術を提案し、受賞等によって一定の評価を受けた。今後は、損傷回避と洗浄を両立可能なハイブリッド新技術の開発と実用化に向けた研究も展開させる。