Velocity of Transient Cavities in an Acoustic Stationary Wave

This paper concerns the high-speed motion of transient cavities generated in an acoustic stationary wave in a cylinder filled with water. Time-exposure photographs are presented of the cavities illuminated by a high-speed stroboscope showing multiple exposures of an individual cavity as it was propelled outward from a region of large acoustic pressure amplitude. The photographs show several interesting details of the cavitation event. Velocities obtained by the cavities were on the order of 1 m/sec, pressure amplitudes on the order of 5 bars, and cavity lifetimes on the order of 10 msec. A theoretical analysis of the cavity motion is obtained by considering the cavity as a spherical inhomogeneity in an acoustic stationary wave. Comparison of theory and experiment show good agreement provided that a velocity-squared drag law is used with a drag coefficient of 0.77.