On the jetting stage of a waterdrop impact by liquid-wedge impact simulation

Waterdrops impacts on steam pipes, turbine blades, aircraft wings, airborne reconnaissance equipment and rocks result in performance degradation and failure. Analytical models provide accurate estimates for the pressure evolution during the initial, high-pressure stage of the impact which is the primary source for the target failure. The high-pressure stage ends when a liquid jet emanates on the target surface ahead of the compression wave. However, the theoretical estimates for the size of the high-pressure domain are considerably smaller than the size of damage sites measured on impacted surfaces. In this work we investigate the reasons for this discrepancy. In analogy with the analytical models, but by application of the finite element method, we examine liquid-wedges impacts. At small gap angles, when the liquid-solid interface grows at a supersonic speed the model is retrieving the analytical results. At larger wedge angles we find that, together with the transverse jetting, the liquid ahead of the wetted region accelerate and close the gap between the liquid and the solid. Consequently, in spite of the transverse jetting, the propagation of release waves from the free boundary is delayed and the pattern of the pressure remains similar to the one for smaller wedge angles. These results are in agreement with the experimental findings and reveal the manner by which the termination of the high-pressure stage is postponed beyond the predictions of the analytical models.