Transient cavitation in high-quality factor resonators at high static pressures.

Abstract

Cavitation collapse can generate intense concentrations of energy, sufficient to erode even the hardest metals and to generate light emissions visible to the naked eye [sonoluminescence (SL)]. The phenomenon of “single bubble sonoluminescence” (SBSL) in which a single stable cavitation bubble radiates light flashes each acoustic cycle typically occurs near 0.1 MPa static pressures. Impulse Devices, Inc. has developed a new tool for the study of SL and cavitation: a high quality factor, spherical resonator capable of achieving acoustic cavitation at ambient pressures in excess of 30 MPa. This system generates bursts of violent inertial cavitation events lasting only a few milliseconds (hundreds of acoustic cycles). Cavitation observed in this system is characterized by flashes of light with intensities up to 1000 times brighter than SBSL flashes as well as spherical shock waves with amplitudes exceeding 100 MPa (1000 bars) at 1 cm from the cavitation center. Computer simulations indicate shock wave amplitudes near the collapsing bubble around 1–10 TPa (10–100 mbars) and liquid temperatures on the order of 5000 K, possibly causing the liquid to become opaque. The implications of these extreme conditions on SL emission will be discussed. [Work funded by Impulse Devices, Inc. ACPT Contract No. W9113M-07-C-0178.]