THE OSCILLATIONS OF A BUBBLE MOVING IN AN INVISCID FLUID

A multiple-parameter perturbation analysis is carried out for the oscillation characteristics of a bubble moving in an inviscid fluid at a constant velocity. It is shown that the quiescent shape of a moving bubble becomes an oblate spheroid, which leads to the removal of the mode degeneracy that exists in the small-amplitude oscillations of spherical bubbles. All characteristic frequencies of the oscillations appear to decrease quadratically with the uniform translation velocity of the bubble. A possible mechanism of coupling between the axisymmetric two-lobed oscillation mode and the quiescent deformation is revealed for the monopole emission of sound by asymmetric bubble oscillations.