INFLUENCE OF CAVITY PRESSURE ON THE DYNAMICS OF WATER-ENTRY CAVITY

摘要

Dynamics of water-entry cavity has been analyzed, therncavity being generated from a solid body impacting andrnpenetrating water at a normal incidence. To describe the cavityrnbehavior, an equation of cavity dynamics is obtained by settingrnup an energy balance equation. As an example of the use of thernmodel, cavity behavior for the water entry of a sphere has beenrnpredicted. For the entry from either a vacuum or greatlyrnreduced atmospheric pressure above the water, the analysisrnpredicts quite a long cavity of an hourglass before deep closure,rnwhich is verified from numerical simulations using a nonlinearrnhydrocode. For the case of atmospheric pressure above thernwater, cavity closure is predicted to occur at water surface.rnAnalytical results for the time of surface closure is comparedrnwith corresponding experimental results. Results indicate thatrnthe cavity pressure drop, at least at the cavity neck, prior tornsurface closure is much greater than previously assumed. Onernof the important parameters which govern the behavior of thernwater-entry cavities is pressure in the cavity. Thus relativelyrnsimple analytical model has been described here to estimaternpressure in the water-entry cavity.