THE GENERATION OF NEGATIVE-PRESSURE WAVES FOR CAVITATION STUDIES

A technique for producing strong focused negative pressure waves in wa ter is described. The method is based on the phase inversion of the pl anar shock wave from an electromagnetic transducer. This is achieved b y reflection and focusing at a pressure release boundary. The acoustic concentrator has a phase inverting central element and a phase mainta ining annular mirror. Focal pressures of approximately -16 MPa from an initial +5 MPa EMAT source have been measured and the focal volume wa s found to be approximately the same as that obtained with a conventio nal ultrasonic lens. The electromagnetic transducer and the parabolic concentrator is an excellent source of cavitation bubbles in water. Th e focused negative wave has been observed using high speed laser-lit S chlieren photography. (C) 1998 Elsevier Science B.V.