A Study of The Motion of Bubbles from Underwater Explosions With Efficient Numerical Solvers

An efficient numerical modeling of multi-fluid flows is used to study the motion of large underwater bubbles. The considered fluids include air, water and high explosive material. The numerical solvers employed follow the physics of these problems. During detonation and recompression all parts are considered compressible. For the three components proper equations of state are used: ideal gas for air, stiffened gas for water, and Jones-Wilkins-Lee (JWL) for the high explosive material. The compressible flow solver employs explicit multi-stage Runge Kutta time integration and a second-order accurate HLLC approximate Riemann solver with linear finite elements for the spatial discretization. A sharpening technique based on the hyperbolic tangent interpolation, i.e., THINC, is adopted to sharpen the transitioning interface. Once the detonation and shock propagation phases(s) have finished, the flow in the water may be considered incompressible and the flow in the bubble of detonation as having no spatial variation in density, velocity and pressure. This allows for the use of incompressible flow solvers and much larger timesteps, easing the computational burden. Different switching indicators are considered.