Multiphase modeling of dynamic fluid-structure interaction during close-in explosion

The modified ghost fluid method (MGFM) developed by Liu et al. (J. Comput. Phys. 2003; 190:651-681) provides us a robust method to treat moving compressible gas-gas and gas-liquid interfaces. Recently, the MGFM was extended to treat compressible fluid-compressible structure interfaces, where the structure was assumed to be very thick or infinitely thick (Comput. Mech. 2007; 40:667-681). In this work, the MGFM is applied to investigate the complex physics that occur during an underwater explosion inside a fluid-filled cylinder. Owing to the refraction of strong rarefaction waves at the fluid-structure interface and inside the thin cylinder wall, cavitation occurs next to the cylinder wall in the fluid; simultaneously, solid tension waves may appear next to the fluid-structure interface inside the structure. Both phenomena tend to cause the implicit double-shock approximate Riemann problem solver (the key component used to predict the fluid-structure interface status in the MGFM) to work less effectively in regions of low pressure and to be invalid when tension waves appear in the vicinity of the fluid-structure interface. To overcome these mentioned difficulties, the MGFM will be further developed in this work. Owing to the high initial pressure, short duration and high intensity of the shock load and cavitation reload, the compressibility of the structure becomes important, and the cylinder can be modeled as a compressible fluid-like medium. The hydro-elasto-plastic equation of state is, thus, used to describe the constitutive behavior of the compressible solid cylinder. A systematic study of the cavitation reload is conducted to examine the influence of the wall material, wall thickness, explosion distance, and explosion strength on the fluid and structural responses.