Resonant coupling of oscillating gas or vapor bubbles in water: An experimental study

Resonant coupling of oscillating gas or vapor bubbles in water is experimen tally studied using a two-frequency acoustic apparatus. First, the threshol d amplitude of resonant coupling between the volume and axisymmetric shape oscillations is measured for gas bubbles in the shape modes, n=3-6, and for vapor bubbles in the modes, n=4 and 5, where n is the mode number. The res ult qualitatively agrees with a theoretical prediction based on a phase-spa ce analysis. Secondly, the efficiency of two coupling conditions, two-one ( 2:1) and one-one (1:1) resonant conditions is compared for the n=4 and 5 mo des. The result of the comparison can be generalized as follows: When n is an even number, the (1:1) coupling condition has better energy transfer eff iciency than (2:1). The relationship reverses when n is an odd number, i.e. , the (2:1) coupling condition has better energy transfer efficiency than ( 1:1). (C) 2000 American Institute of Physics. [S1070-6631(00)00202-6].