Evolution of the air cavity during a depressurized wave impact. II. The dynamic field

The present paper on wave-impact events in depressurized environments completes the analysis of Part I by focusing on the dynamical features of the impacts and on the influence of the ambient pressure. Connection is made between the impact regimes typically described in the literature and the stages described in Part I [C. Lugni, M. Miozzi, M. Brocchini, and O. M. Faltinsen, “Evolution of the air cavity during a depressurized wave impact. I. The kinematic flow field,” Phys. Fluids 22, 056101 (2010)]. The stages of isotropic/anisotropic compression and expansion of the air cavity are of particular interest. The impact duration at the wall is almost independent of its height above the undisturbed surface level, but its intensity rapidly decreases in the body of the fluid (the peak pressure halves within the first two compression/expansion cycles). The time evolution of the pressure loads on the wall is analyzed by means of the Hilbert transform and an empirical mode decomposition of the signals. This enable...

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