Bubble-pair: A tool for the cell perforation and particle fragmentation*

When a cavitation bubble collapses near a rigid surface, it creates a high-speed transient microjet that impinges and accelerates liquid onto the surface and produces intense mechanical shearing. An interacting bubble-pair arrangement can control the direction of these ensuing microjets, allowing for precise use in different applications. Although the shear stress caused by the collapse of a bubble has been extensively studied, the underlying dynamics of an interacting bubble-pair is less understood. Measuring these stresses in high spatial and temporal resolution is experimentally demanding and challenging; consequently, the data on bubble-induced flow fields are scarce. It is believed that the nearby surfaces and their curvature substantially influence the dynamics of collapsing bubbles. Using an axisymmetric compressible solver, we study the shear stress induced by interacting bubble-pair close to flat and curved rigid surfaces. By comparing the bubble shapes and shear stress for both surfaces, we observe that the maximum stresses are formed following the impact of the jet during its radial spreading. We expect this interacting bubble-pair arrangement may open new avenues in the field of cell perforation and be used as a tool for particle fragmentation.