DYNAMICS OF A MICRO-BUBBLE BETWEEN TWO SPHERICAL PARTICLES

The effects of high intensity ultrasound field in water and the resulting volume oscillations of one underwater micron-sized gas bubble initially resting between two larger but micron-sized solid particles are numerically studied. The model assumes that the two particles remain at rest while the bubble changes its shape in the presence of the particles. Specifically, this study predicts the bubble's expansion, collapse, and interaction effects with the adjacent two solid spherical particles which are not necessarily of equal size. The model assumes that the flow surrounding the bubble and two particles is incompressible. A 2-D Finite Element method which is capable of tracking the ultra fast moving boundary of the bubble is developed and an associated computer program is written to solve the modeled equations and boundary conditions. In the absence of a similar study in the literature, the validation (although not shown here) of the numerical method is carried out by solving the expansion and collapse of a single bubble initially resting in an infinite extent of fluid for which theoretical results are well-known in the literature. A good agreement is obtained between the numerical and theoretical results [18]. Numerical results for the temporal shapes of the bubble, its lifetimes for various parametric cases are provided and discussed. The variations of the pressure and the velocity fields in the liquid surrounding the bubble and two particles are also analyzed and discussed.