Investigation of free-field underwater explosion with Eulerian finite element method.

Abstract Underwater explosion in free field is investigated in this paper numerically. With the multiphase interface captured by the Volume of Fluid (VOF) method, the Eulerian finite element method (EFEM) for underwater explosion is established. The MUSCL algorithm to advect the element centered variables is modified to maintain its conservativeness in the axisymmetric model, and the second order Early Time Approximation (ETA 2) is adopted to deal with the non-reflecting boundary condition of the computational domain. By comparing with the experiment results, the numerical model is proved in both shockwave and bubble oscillation simulation. With the numerical model, 2 underwater explosion cases with different initial depths are simulated and the near-field pressure characteristics are analyzed. The near-field bubble pulsation load exhibits noteworthy asymmetry around the bubble, which is attributed to the 2 high pressure regions above and beneath the bubble, respectively. By comparing the evolution of bubbles with different buoyancy parameters, it is found that the increase of the buoyancy parameter can delay the penetration and extend the collapse of the bubble. Highlights • The present numerical model can predict both the shockwave and bubble pulsation load with good accuracy. • The non-reflecting boundary condition based on ETA2 works well in the underwater explosion simulation. • The MUSCL algorithm is modified for the convection in the axisymmetric model. • The asymmetry of the pulsation load is generated by the 2 high pressure regions caused by gravity and the jet impact. [ABSTRACT FROM AUTHOR]