Shock-Induced Atomization of Sessile Droplets

We investigate the shock-induced atomization of sessile water droplets with varying wettability. A Mach 1.26 shock wave, generated by diaphragm rupture in a shock tube, interacts with the hydrophobic and hydrophilic droplets. Breakup dynamics are captured through high-speed imaging and 3D simulations in OpenFOAM, employing the Volume of Fluid (VOF) method, Large Eddy Simulation (LES), and adaptive mesh refinement. Experiments and simulations reveal that hydrophobic droplets develop peak structures on the windward and leeward sides, while hydrophilic droplets form a thin liquid film on the wall. Peak formation is driven by localized high pressures from shock reflections and stagnation zones at the contact line, enhanced by the droplet’s convex geometry. In contrast, liquid film formation is associated with windward vortex development in low contact angle droplets. Analysis of Rayleigh–Taylor (RT) and Kelvin–Helmholtz (KH) instabilities shows that KH behavior is largely insensitive to contact angle, while RT instability produces shorter windward wavelengths as wettability increases.