A practical simulation of a hexanitrohexaazaisowurtzitane (CL-20) sphere detonated underwater with the Taylor wave solution and modified Tait parameters

The modified ghost fluid method (MGFM) has been one of the most popular and successful algorithms for coping with the numerical calculation of multi-medium flows, especially for the interaction between strong discontinuities and material interfaces. To apply the advanced algorithm to an underwater explosion simulation, first, the uniform distribution of the state of the detonation products, which is the most generally used initial condition in an explosion simulation, is replaced by the analytic solution of the Taylor wave. The Tait equation is, then, expanded to a broader pressure coverage of up to 100 GPa to match the initial state at the discontinuity. One-dimensional Euler equations with source terms governing the explosion flow are discretized with the fifth-order weighted essentially non-oscillatory scheme in space and the third-order Runge-Kutta scheme in time. The gas-water interface is tracked with the level set equations, and the intermediate states are resolved and defined by following the MGFM. In addition to the comparative studies among diverse numerical cases, experimental data were offered as a calibration in this work. The temporal and spatial distribution characteristics of the energy and flow variables were comprehensively discussed. Studies and analysis showed that (1) the novelly achieved parameters B = 710.8 MPa and γ = 5.22 for the Tait equation of state were highly recommended for any application involving transient loads. (2) The explosion flow field produced by the Taylor wave model was closer to the nature of physical reality. (3) Without considering the details, the stationary wave model was not entirely unacceptable as an initial condition for roughly simulating an explosion effect. The most important thing was that one had to ensure that the initial energy was equivalent to the Taylor wave case.