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 / ts where the time t0 is the characteristic time for cavitation bubble collapse and the time ts 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.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call