Subharmonic Waves Generation by Parametric Decay of Bubble Oscillations

概要

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It is well known that subharmonic ultrasonic waves are generated in liquid when acoustic cavitation occurs. In order to confirm this experimentally, generation of subharmonic ultrasonic waves in water was undertaken and various subharmonic waves of the orders such as 1/2, 1/3, 2/3, 1/4, and nonrational number ratio were detected, in addition to first and higher-order harmonic waves. The generation mechanism of the subharmonic waves was discussed based on a model of the nonlinear interaction between ultrasonic waves and bubbles. The pumping wave that generates the subharmonic waves is considered to be radial bubble oscillation in unison with the input frequency, due to the energy received from the ultrasonic waves. This oscillation, in turn, emits ultrasonic waves with subharmonic frequencies through parametric decay when certain matching conditions in the dispersion relation are fulfilled. This process can be treated as analogous to that of an acoustic phonon.
社団法人応用物理学会の論文
1997-05-30