Numerical Modeling of Small Scale Water Mitigation Feasibility Tests

摘要

Water placed in the vicinity of explosives in a confined environment has been found to significantly mitigate the quasi-static gas pressure from an explosion. Reports on several small scale tests available from the open literature confirm that gas pressures can be reduced by up to 90%. This is of significant importance for the safety of explosive facilities wherein the gas pressure from an explosion controls debris distance. Analytical and numerical models are needed to model the effects of water mitigation and to predict the resulting gas pressure. A series of calculations using the AUTODYN software program were performed to simulate three small scale feasibility experimental tests of explosions inside rigid chambers. Each of the tests is represented in a simplified form by an axisymmetric two-dimensional model with and without the presence of water. Each test includes a configuration wherein the water is placed close to the explosive such that the explosive may be considered to be immersed in the water. In addition, in one of the test series, the water was placed only on the sides of the explosive in order to determine the effect of water placement on the final gas pressure. The three simplified models were analyzed using AUTODYN in its standard release form. Additional calculations were then made with AUTODYN modified through use of a user subroutine to account for heat transfer effects not represented in the standard version of the program. The correlation of numerical and experimental results for the bare charge situations was quite good. Introduction of the water into the tests, and using AUTODYN in its standard form, does provide a mitigation of the gas pressure, but not to the extent as evidenced in the experiments. When the effects of heat transfer between explosive products and water/vapor are included in the model, the gas pressures are further reduced to levels generally within the range observed in the experiments.