Numerical analysis of the interaction of two underwater explosion bubbles using the compressible Eulerian finite-element method

Abstract

This paper presents numerical investigations of the nonlinear interactions between two underwater explosion (UNDEX) bubbles using the compressible Eulerian finite-element method (EFEM). The volume of fluid method is applied to capture the multi-fluid interface. In this model, the high-temperature and high-pressure gaseous products inside the UNDEX bubble are described by the equation of state for Jones–Wilkins–Lee, which allows us to consecutively simulate the propagation of the primary explosion shock wave and multi-period bubble pulsations. To verify the efficiency and accuracy of the present model, comparisons with experimental data are performed, showing that both the dynamic behaviors of oscillating bubbles and the pressure profiles of primary shock waves, bubble pulsations, and jetting loads are highly consistent. In addition, it is found that the EFEM model can satisfactorily reproduce the complex characteristics of interacting bubbles, such as the coalescence and splitting that occur during later pulsating cycles in bubbles. On this basis, the effects of the initial bubble–bubble distance γbb and buoyancy parameter δ on the features of bubble interactions and the corresponding pressure loads in the flow field are analyzed and discussed. In particular, the pressure induced by two identical UNDEX bubbles (each generated by detonation of an explosive with weight W) is compared to that induced by a single bubble generated by an explosive with weight W or 2W to provide the basic technical support and reference for the design of multiple-weapon attacks in military engineering applications.

Theoretical study on bubble dynamics under hybrid-boundary and multi-bubble conditions using the unified equation

“…The deviation between the theoretical migrations and the experiment occurs mainly in the second and later cycles and could be due to complex factors, including the non-spherical bubble behavior induced by gravity or boundaries, such as jetting, splitting, and phase transition. In addition, we also calculated the time histories of the radius and migration for a large-charge underwater explosion bubble, and compared them with the results from the Euler finite element method (EFEM) [72,92], as shown in Figure 6. EFEM is a numerical method used to solve the compressible Euler equation system.…”

“…The above studies used numerical simulations and experiments to investigate bubble dynamics in different environments in most cases. Numerical methods, such as boundary element [66][67][68][69][70], finite element [71][72][73], finite volume [74][75][76], and smooth particle hydrodynamics methods [77,78], have been greatly developed in the past decades for predicting bubble behavior and revealing its underlying mechanism. Experimental methods, such as laser pulse [79][80][81][82], electric discharge [42,[83][84][85], and small charge underwater explosions [19,86,87], are mature.…”

Volume-adaptive SPH simulation of structural damage subjected to underwater contact explosion

“…Sophisticated algorithms and schemes were utilized to discretize the convective terms and the temporal term, making the model suitable for underwater explosion problems characterized by transience, multi-phase interaction, and large deformations. Yu et al [18] presented a comprehensive CFD model and solver for simulating compressible multiphase flow in underwater explosions. This model was validated for several underwater explosion problems in a free field, near a free surface, and near a rigid dam.…”

Numerical simulation of cavitation-bubble expansion and collapse inside a bottle subjected to impact on its topside

“…In numerical research, many methods such as the boundary element method, level-set method, Eulerian finite element method and volume of fluid (VOF) method have been used to describe the dynamic behavior of the bubble (Akhatov et al, 2001;Lauer et al, 2012;Liu et al, 2018;Liu et al, 2020;Luo, 2008;Méndez & González-Cinca, 2011;Peng et al, 2019;Tang et al, 2020). Among these, the VOF method was used by Koukouvinis to study the aspheric collapse of bubble subject to gravity (Koukouvinis et al, 2016a(Koukouvinis et al, , 2016b.…”