Numerical Simulation of Collapsing Behavior of Bubble Clouds.

In order to investigate the complex behavior of collapsing bubbles in cloud cavitation, numerical simulations have been performed by solving the 2-D governing equations for gas-liquid two-phase media. Here, the equation of state for such media is derived from the locally homogeneous assumption, so that the apparent compressibility can be taken into account. The interface of a bubble or a cloud of bubbles is treated as a contact discontinuity surface, where the values of density and void fraction are allowed to jump. When the void fraction in a bubble cloud is almost 100%, the collapsing behavior agrees well with that of a single bubble. Numerical results of the interaction between some bubbles and an incident shock wave show qualitative agreement with experimental results. Therefore, complex interaction phenomena between multibubbles can be simulated when some small bubbles are arranged in a bubble cloud by distributing the corresponding void fractions nonuniformly.