Cavitation Bubbles inside Spherical Water Drops in Microgravity

We studied spark-generated bubble inside stable water drops produced in microgravity. The closed and isolated liquid geometry results in a unique confinement of subsequent shockwaves, since the latter bounce of the free surface. This setting results in an amplified form of secondary cavitation, and proofed particularly useful to study the coupling between shockwaves and secondary cavitation. High-speed visualizations and 3D computer simulations reveal that focus zones in the shockwave propagation lead to a strongly increased density of secondary cavitation. Considering shockwave crossing and focusing may hence prove crucially useful to understand the important process of cavitation erosion.