Oscillation of a transient bubble between two parallel plates with cylindrical bulges

Abstract

The dynamic behavior of a transient bubble oscillating between two rigid flat plates with internally mounted cylindrical bulges is studied numerically using the finite volume-based open-source software OpenFOAM-V6. Three different bulge radii with constant height are considered and the results are compared with the case of bare walls (i.e., walls without bulges). The radii of the considered bulges are half, equal to and twice the initial radius of the bubble. Based on the local Mach number, the flow of the fluid inside the bubble (gas phase) is considered compressible, while the flow of the fluid outside the bubble (liquid phase) is incompressible. Both phases are viscous, non-isothermal and immiscible and there is no mass exchange between them. The results are given in terms of bubble shape, velocity vectors and pressure field. It was found that the presence of the bulges reduces the overall lifetime of the bubble comprising the expansion, collapse, split, rebound and toroidal stages. Of the three bulge diameters considered, if the bulge diameter is equal to the initial diameter of the bubble, the lifetime of the bubble will be longer. Besides, at all the stages of its lifetime, the bubble shape is affected by the bulge diameter due to the ensuing different pressure fields. The results of the present work may be potentially useful in such applications as electro discharge machining (EDM) and cardiovascular treatment.