Inertial collapse of individual bubbles near a solid surface*

Inertial collapse of cavitation bubbles is an essential research topic to a variety of applications ranging from naval hydrodynamics to medicine and energy sciences. The bubble implosion, which concentrates energy into a small volume, can produce high pressures and temperatures, emit strong shock waves, and radiate visible light. One of the main consequences of cavitation is structural damage to neighboring surfaces. To better understand such flows, we use highly resolved numerical simulations of Rayleigh collapse of a single bubble as well as a bubble pair near a rigid wall. We explain that the presence of a rigid boundary and the inter-bubble interactions hinder the energy concentration, give rise to the momentum of non-converging motions, break the flow symmetry, and leads to lower pressures and temperatures. By developing scaling laws for certain collapse properties, we illustrate that single bubbles collapse in a universal, thus predictable fashion. However, collapse of a bubble pair shows a far more complicated behavior and breaks the single-bubble scalings. Thus, the value of such simulations to develop scaling laws for the collapse of many bubbles is debatable at the present time.