Sameer I. Madanshetty
Dept. of Aerosp. and Mech. Eng., Boston Univ., 110 Cummington St., Boston, MA 02215
Acoustic microcavitation in water is studied primarily at 1 MHz and 1% duty cycle. To detect cavitation two kinds of acoustic detectors are used. The first one is an unfocused, untuned 1-MHz receiver transducer that serves as a passive detector. The other one is a focused 25-MHz transducer that is used in the pulse-echo mode and is called the active detector. Cavitation itself is brought about by a focused LZT-1, 1-MHz crystal driven in pulse mode. The active detector is arranged confocally with respect to the cavitation transducer. Both the interrogating pulse and the cavitation pulse arrive simultaneously at the common focus, which is the region of cavitation. With the test chamber filled with clean water no cavitation is observed, even when the cavitation transducer is driven to give its peak output. Cavitation is, however, observed when microparticles are added to the host water. How these smooth, spherical, monodispersed, microparticles give rise to cavitation is described with some predictions, and corroborating experiments. It is found that the weak, high-frequency detection field affects the cavitation environment significantly.