Cloud Cavitation and Collective Bubble Dynamics

摘要

The study described in this report extends our knowledge of single bubble dynamics to multibubble dynamics. Within the restriction of characteristic bubble size small compared to interbubble distance, the dynamics of a bubble cloud is investigated. Dynamic effects in absence as well as in presence of heat and mass transfer at the bubble wall are considered. The matched asymptotic expansion method is used and enables derivation of differential equations for the bubble shape components at the various orders of approximation. These were solved numerically and the pressure field was deduced. When, during a significant portion of the imposed pressure field history, the liquid is superheated or gas supersaturated, heat and mass transfer at the interface interfere with the dynamics of the bubble growth or oscillations. In that case, the dynamic equation of a bubble in the cloud is coupled to the heat or mass transfer equation by the value of the partial pressures of the liquid vapor and noncondensible gas inside the bubble which are then transfer dependent. This problem is solved when the liquid properties or conditions are such that the variation of the liquid temperature of the gas concentration in the liquid occurs primarily in a thin boundary layer at the bubble wall. In that case an integral equation relates bubble dynamics and heat or mass transfer at the bubble interface.