Fragmentation of water drops in collision with a small obstacleстатья
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Дата последнего поиска статьи во внешних источниках: 26 января 2024 г.
Аннотация:The study is dedicated to the general features of the processes of deformation and fragmentation ofliquid drops have been studied when they collide with obstacles. Masks and filters, protecting againstairborne infections, are among the possible obstacles. Coughing, sneezing, and talking cause theejection of drops of saliva and bronchial mucus. A local drop-mask or drop-filter collision is modeledby the impact of a drop on a small obstacle as the simplest hydrodynamic case with a minimumnumber of influencing factors. For water-based oral and bronchial drops with a typical diameterdi = 100 ¹m and impact velocity of the order of vi = 10 m/s, the impact Weber number is aboutWei = ½v2idi=° = 139. As a starting point in the problem of the drop breakup in a collision with asolid obstacle, we consider the coaxial impact of an inviscid liquid drop with a diameter of 2.8 mm ona disk with a diameter of 4.0 mm. In laboratory experiments, the similarity was provided by impactvelocities of 1.88–3.57 m/s, which gives impact Weber numbers Wei = 137–496. Such collisionsare controlled only by inertia and capillarity, while the influence of all other factors is negligible.A round liquid lamella with a torus-shaped rim is formed upon the collision. The rim first expandsand then retracts, forming radially directed liquid fingers in the rim. At low impact velocities, thefingers retained continuity, while at sufficiently high velocities, the fingers spattered into secondarydroplets. Experiments have shown that the critical Weber number corresponding to the transitionto spattering lies between 137 and 206. Approximately the same values of the Weber number occurwhen infected drops hit masks or filters.