Underwater weapons effect - concepts and aspects of simulation

This report describes some concepts of weapon effects as well as describes some issues when simulating these phenomena. Joint shock waves are possible to achieve in a chosen position. This would result in enhanced peak pressure when the charge is divided in two, or more, charges with the same total weight. Results from experiments show that ,under perfect condition, a 40% increase in peak pressure and 20% increase in maximal strain are possible. An investigation if shock wave energy or bubbel energy give the most effect was conducted. Two simulations were performed where the difference was the explosive. One with more energy in the bubble and opposite for the other. A small increase in effect was detected when bubble energy increased although a more elaborated investigation is needed in order to draw conclusions. A small concept adapted to small and maneuverable underwater vehicles is beeing developed. An experiment preceeded by simulation to determine the shape were conducted. A succesful function and good agreement were achieved. When the shock wave sweeps the target there has been some difficulty to achieve the correct translation of forces. Comparison of experiment and simulation in order to explain why this is the case is performed but needs more investigation. When plasticity occurs it is concluded that simple material models are not enough to represent material behaviour when simulating effects of underwater explosions.