In this paper, a multi-phase SPH method is applied to the dynamic modelling of large-scale bubbles. Firstly, the robust multiphase SPH model and related numerical treatments are briefly recalled. Then, the characteristics of bubble movement in water are studied, and the effects of bubble radius and initial depth on bubble motion are analyzed. Finally, the breaking process of a large-scale rising bubble at free surface is simulated, and the characteristics of bubble-free-surface interaction under various factors are studied.
When a large-scale bubble released near a floating body, it may cause great impact on the floating state and stability of the body. For example, when the combustible ice crystal located at seafloor are disturbed by geological activity, it may vaporize rapidly and produce a large number of bubbles to rise to the surface. In severe cases, a single large scale bubble will cause the capsizing of the entire hull, such as the case described by May and Monaghan (2003). Therefore, it is of great significance to study the dynamics of large-scale bubbles.
Early researchers have done a lot of work on bubble dynamics, and have achieved good progress. However, some challenges have not been solved yet. Among these technology methods to deal with interface, interface tracking method (ITM) is a relatively accurate one as proved by Hua et al. (2008). However, the mesh reconstruction is required when dealing with the interface tear or fusion. Volume of fluid (VOF) (see Annaland et al., 2005; Li et al., 2018; Abbassi, et al., 2018) and level set (LS) in Croce et al. (2010) rely on additional fluid variables (specific heat rate, void fraction, mass fraction, etc.) to distinguish the gas and liquid phases.
The numerical implementation is relatively easy. However, it suffers from numerical dissipation and the non-conservation of mass. Different from the previous methods, boundary element method (BEM) only discretizes the bubble surface, so it is of higher efficiency. However, Zhang et al. (2015) pointed out that it's hard for BEM to consider the fluid viscosity effects and vortices. By applying an enhanced stabilized moving particle semi-implicit (MPS) method, Khayyer and Gotoh (2013) simulated a bubble rising in water which is featured by high density ratios. The numerical results show that a relatively smoother interface can be obtained and unphysical gaps between the phases are removed.