Observation of the growth of cavitation bubble cloud by the backscattering of focused ultrasound from a laser-induced bubble

T. Horiba; T. Sano; T. Ogasawara; H. Takahira

doi:10.1117/12.2270465

20 February 2017 Observation of the growth of cavitation bubble cloud by the backscattering of focused ultrasound from a laser-induced bubble

T. Horiba, T. Sano, T. Ogasawara, H. Takahira

Author Affiliations +

Proceedings Volume 10328, Selected Papers from the 31st International Congress on High-Speed Imaging and Photonics; 1032819 (2017) https://doi.org/10.1117/12.2270465
Event: 31st International Congress on High-Speed Imaging and Photonics, 2016, Osaka, Japan

Abstract

The present study is concerned with the cavitation inception and the growth of a cavitation bubble cloud by the backscattering of focused ultrasound from a laser-induced bubble. The cavitation inception close to the interface of a laser-induced bubble has been observed by a high-speed video camera with the frame rate of up to 1.25 Mfps, and its location and the successive cavitation cloud growth are discussed for various ultrasound conditions. It is shown that the normalized distance between the cavitation inception location and the bubble interface by the wavelength of ultrasound is an increasing function of η = t₀ / t_s where the time t₀ is the characteristic time for cavitation bubble collapse and the time t_s the period of ultrasound. Also the magnitude of the dimensionless distance is about 0.05-0.3 times of the wavelength of ultrasound, and the positive pressure threshold of ultrasound for a cavitation inception is about 35 MPa. It is also shown that the cavitation bubble cloud by the backscattering of the incident ultrasound grows conically along the propagation axis of the focused ultrasound. As the incident focused ultrasound pressure at the focus becomes stronger or the duration of the focused ultrasound becomes longer, the cavitation bubble cloud grows larger. However, even though the ultrasound duration becomes longer, this growth ends up and reaches a limited value when the cavitation bubble cloud grows out of the focal region of the focused ultrasound.

Citation Download Citation

T. Horiba, T. Sano, T. Ogasawara, and H. Takahira "Observation of the growth of cavitation bubble cloud by the backscattering of focused ultrasound from a laser-induced bubble", Proc. SPIE 10328, Selected Papers from the 31st International Congress on High-Speed Imaging and Photonics, 1032819 (20 February 2017); https://doi.org/10.1117/12.2270465

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