High-fidelity simulation of an aerated cavity around a surface-piercing rectangular plate

A bluff body advancing through the water surface at high Froude number produces intricate two-phase flow patterns. One intuitive feature is an entrapped air cavity which subsequently breaks apart into a mass of droplets and bubbles. The bluff-induced cavity partially accounts for the appearance of bubble clouds in the wake. However, few experimental or numerical studies have been devoted to this phenomenon. To clarify this mechanism, high-fidelity simulations are performed to emphasize the evolution of the aerated cavity generated by a surface-piercing rectangular plate. First, the mesh independency study is performed to validate the trend of the convergence of the time-averaged wave profile, the bubble size distribution, the bubble number density, and the entrapped bubble volume. Then the formation and development of the aerated cavity induced by a surface-piercing plate with various yaw angles (αE∈[10∘,50∘]) are investigated. Numerical simulations show that the air pocket is entrapped and develops with stabilized rotational motion, and the subsequent breakup of the air pocket constitutes the leading cause of the bubbly wake. The geometrical characteristics of the aerated rotation cavity are summarized as a function of yaw angles. Moreover, with the adaptive mesh strategy and high-resolution schemes, all the bubbles of equivalent radius r≥2mm are captured and tracked, so the spatial and size distribution laws of the varying-sized bubbles pinching off from the air cavity in the wake are summed up. In addition, large-scale coherent structures wrapped around the cavity and the effects on air entrainment are discussed.