Experimental and numerical investigations on the explosions nearby a free surface from both sides.

The explosion near a free surface is a complex multiphase flow problem involving large deformation and even fragmentation of the fluid interface. Experiments and numerical simulations are presented to investigate the transient fluid dynamics of explosions approaching the free surface from the air and water sides. The numerical model is established based on the Eulerian finite element method and the Volume of Fluid method. The explosion experiments are conducted in a water tank. We classify the problem into cavities and bubbles according to whether the explosive is exposed to the air. Explosions above the free surface generate hemispherical cavities that evolve into W-shaped ones after an upward jet develops from the bottom. The hemispherical cavity will close if the explosion is close enough to the free surface. The simulations reveal that the distance parameter dominates the bubble's bursting and that the explosive equivalent and distance parameter compete to determine the cavity's closure. In addition, the impact pressure characteristics generated by the explosion near the free surface are also analyzed. • An axisymmetric Eulerian FEM model is presented to investigate the explosion near the free surface. • Explosion experiments with different standoff distances from the free surface are carried out. • The factors influencing cavity closure and bubble bursting are analyzed. • The impact pressure characteristics generated by the explosion near the free surface are analyzed. [ABSTRACT FROM AUTHOR]