Direct observation of shockwaves, cavitation, and jetting inside liquid droplets during high-speed impactAgrež, Vid (Avtor) Gonzalez-Avila, Silvestre Roberto (Avtor) Horvat, Darja (Avtor) Xie, Run-Ze (Avtor) Zeng, Qingyun (Avtor) Petkovšek, Rok (Avtor) Ohl, Claus-Dieter (Avtor) cavitationdroplet impactshockwavesacoustic focusinghigh-speed imagingThis study reports direct experimental observations of shockwave propagation and cavitation bubble formation inside liquid water droplets during high-speed impact (80 –180 m/s) on solid surfaces, together with jetting observed at the distal end of the droplet. Ultra-high-speed shadowgraph and angle-view imaging at 10 million frames per second resolved two distinct internal wave structures: a primary compression front (1500–2050 m/s), consistent with pressure-dependent corrections to the acoustic wave speed, and a secondary tension wave emerging approximately 500 ns later, generated by reflection at the curved water–air interface. The curved distal surface focuses converging rarefaction waves into a caustic region, leading to cavitation nucleation 1.2–1.5 µs after impact. The subsequent asymmetric collapse of these cavitation structures drives directed jetting from the distal end, with jet morphology dependent on droplet geometry: coherent jets for smaller spherical droplets (<2 mm) whereas spray-like ejection is typical for larger, elongated droplets (>2 mm). At the proximal end of the droplet, air is entrapped between the surface and the droplet, collapsing into a toroidal-shaped bubble that exhibits oscillations in the 0.5–1.8 MHz range. All presented results, including experimental data and accompanying analysis, provide benchmark validation data for computational models of compressible droplet impact.20262026-11-06 11:29:21Članek v reviji190890sl