Mathematical model of cavitational braking of a torus in the liquid after impact

The process of cavity formation under vertical impact and subsequent braking of a torus of an elliptical cross-section semisubmerged into a liquid is investigated. The solution of the problem is constructed by means of a direct asymptotic method, effective at small times. A special problem with unilateral constraints is formulated on the basis of which the initial zones of a separation and contact of liquid particles are determined, as well as perturbations of the internal and external free boundaries of the liquid at small times. Limit cases of a degenerate and a thin torus are considered. In the case of a thin torus, the flow pattern corresponds to the 2D problem of cavitation braking of an elliptical cylinder in a liquid after a continuous impact.