Wave-in-deck loads induced by regular wave impact: The role of compressible air entrainment

Abstract

During the process of wave-in-deck when waves impacting a horizontal platform deck from below, large air cavity entrainment would be generated between the free wave surface and the deck. The air entrainments are compressed and expanded during the process of wave impacts. As the momentum and energy exchange medium in the interactions between waves and the structure, air entrainments conversely influence the forces on the deck, risking structural safety. The key to dealing with the air entrainment is the combination of the mass source wave method and pressure-based compressible technique in capturing the cavity volume variation. In this work, the advanced compressible two-phase model is first developed with our in-house solver to simulate a regular wave impacting a fixed flat plate. The air cavity kinematics/dynamics and their relationship with wave impact features in the process of wave-in-deck impacting are discussed, and the mechanism of the compression/expansion effect is carefully analysed. Two distinct impacting types, direct water impact and entrained-air impact, are identified in this work, and the larger wave impacting pressures in the latter situation with compressible air layer is demonstrated. The good comparison of the numerical results and laboratory data on pressure features reveals that the proposed model is capable of reproducing the nonlinear entrained-air wave impacts and accurate oscillating pressures on a flat deck for applications.