Under Water Explosion Pressure Prediction and Validation Using ANSYS/AUTODYN

Behavior of blast wave due to underwater explosion is of interest to ship designers and metal forming community. Underwater explosion is, also a potential hazard to the water intakes or plant spent fuel pool. Therefore in this paper blast wave propagation in underwater explosion is studied using commercial program ANSYS/AUTODYN. One of the most important far field parameter, pressure obtained from analytical method has been compared with simulation result obtained from ANSYS/AUTODYN. The blast pressure is highly dependent of water incompressibility. The incompressibility of water in AUTODYN can be modeled using different Equation of States. This paper also has the details of different material models available to model water in AUTODYN and its effect on blast pressure. In this paper pressure generated due to under water explosion (explosion of TNT) have been measured at different standoff distances using ANSYS/AUTODYN. Two Equations of States #1 shock, #2 polynomial available in AUTODYN are used to model the water and its results are compared with analytical solution. The underwater explosion is modeled using 1D analysis of AUTODYN with Multi-Material solver. TNT and Water materials are taken from AUTODYN material library. A detonator is placed at the center of TNT to start the ignition. Results are highly dependent on mesh size, for most refined mesh (0.5mm) and at the farthest stand off point there is difference of 0.8 % with analytical solution using shock Equation of state. However with the same mesh size there is difference of 17 % using polynomial Equation of state.