20.500.12556/RUL-168752 Bubble nucleation and jetting inside a millimetric droplet In this work we present experiments and simulations on the nucleation and successive dynamics of laser-induced bubbles inside liquid droplets in free-fall motion, i.e. a case where the bubbles are subjected to the influence of a free boundary in all directions. Within this spherical millimetric droplet, we have investigated the nucleation of secondary bubbles induced by the rarefaction wave that is produced when the shock wave emitted by the laser-induced plasma reflects at the drop surface. Interestingly, three-dimensional clusters of cavitation bubbles are observed. Their shape is compared with the negative pressure distribution computed with a computational fluid dynamics model and allows us to estimate a cavitation threshold value. In particular, we observed that the focusing of the waves in the vicinity of the free surface can give rise to explosive cavitation events that end up in fast liquid ejections. High-speed recordings of the drop/bubble dynamics are complemented by the velocity and pressure fields simulated for the same initial conditions. The effect of the proximity of a curved free surface on the jetting dynamics of the bubbles was qualitatively assessed by classifying the cavitation events using a non-dimensional stand-off parameter Y- that depends on the drop size, the bubble maximum radius and the relative position of the bubble inside the drop. Additionally, we studied the role of the drop's curvature by implementing a structural similarity algorithm to compare cases with bubbles produced near a flat surface to the bubbles inside the drop. Interestingly, this quantitative comparison method indicated the existence of equivalent stand-off distances at which bubbles influenced by different boundaries behave in a very similar way. The oscillation of the laser-induced bubbles promotes the onset of Rayleigh–Taylor and Rayleigh–Plateau instabilities, observed on the drop's surface. This phenomenon was studied by varying the ratio of the maximum radii of the bubble and the drop. The specific mechanisms leading to the destabilisation of the droplet surface were identified. bubble dynamics shock waves droplet cavitation dinamika mehurčkov udarni valovi kapljice kavitacija true false true Angleški jezik Slovenski jezik Članek v reviji 2025-04-23 10:03:19 2025-04-23 10:03:20 2025-04-24 04:03:32 0000-00-00 00:00:00 2023 0 0 Str. A19-1-A19-35 Vol. 968 Aug. 2023 0000-00-00 Zaloznikova Objavljeno NiDoloceno 0000-00-00 0000-00-00 0000-00-00 532.528 0022-1120 10.1017/jfm.2023.542 176638723 Rossello_..._-Bubble.pdf Rossello_..._-Bubble.pdf 1 E5299C3004BCB5554B0CC2105BE7B514 0a499376ed4ccb58f9452500ebc0064017a0c0746d4a0408b6bda8cf28692067 8524b1d5-2018-11f0-b232-0050569b8976 https://repozitorij.uni-lj.si/Dokument.php?lang=slv&id=209667 https://www.cambridge.org/core/journals/journal-of-fluid-mechanics/article/bubble-nucleation-and-jetting-inside-a-millimetric-droplet/B93F08E9B8D85633CDAF27DEDBAAD033 1 487409d9-2018-11f0-b232-0050569b8976 https://repozitorij.uni-lj.si/Dokument.php?lang=slv&id=209666 Fakulteta za strojništvo 0 0 0