Laser-Induced Single Cavitation Bubble Dynamics in the Presence of Microscale Roughness

Cavitation-induced erosion presents major problems for hydraulic and marine systems due to the collapse of bubbles near solid boundaries. This work investigates a passive control technique employing a microstructured rough surface to reduce erosion. High-speed imaging studies were performed to analyze the collapse dynamics of a single bubble induced by laser-generated plasma near a microscale rough surface and a smooth surface. The bubble's equivalent radius was investigated over time for three varying relative wall distances, and its behavior was assessed over three specific phases: growth, collapse, and rebound. The bubble adjacent to the smooth surface demonstrated a symmetrical collapse and formed toroidal structures affixed to the wall, in accordance with established bubble-wall interaction phenomena documented in prior research. The rough surface, on the other hand, caused an asymmetric collapse and rebound, causing a counter-jet to form that moved away from the surface. This divergence from the anticipated symmetric collapse indicated that microscale roughness substantially influences bubble dynamics, diminishing microjet momentum and the associated toroidal cavity size, thus alleviating erosion. These results provided innovative perspectives on cavitation control strategies through surface modification.