We present a multiscale approach to simulate the impact of a solid object ona liquid surface: upon impact a thin liquid sheet is thrown upwards all aroundthe rim of the impactor while in its wake a large surface cavity forms. Underthe influence of hydrostatic pressure the cavity immediately starts to collapseand eventually closes in a single point from which a thin, needle-like jet isejected. Existing numerical treatments of liquid impact either consider thesurrounding air as an incompressible fluid or neglect air effects altogether.In contrast, our approach couples a boundary-integral method for the liquidwith a Roe scheme for the gas domain and is thus able to handle the fully\emph{compressible} gas stream that is pushed out of the collapsing impactcavity. Taking into account air compressibility is crucial, since, as we showin this work, the impact crater collapses so violently that the air flowthrough the cavity neck attains supersonic velocities already at cavitydiameters larger than 1 mm. Our computational results are validated throughcorresponding experimental data.
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