Blast Mitigation Using Water - A Status Report

Abstract : The need to mitigate the effects of blast waves has been heightened by the recent incident with the USS Cole. In the spirit of one of the findings of the DoD USS Cole Commission, that there is a need for, 'More responsive application of currently available military equipment, commercial technologies, and aggressive research and development', this report reviews the current knowledge base on blast mitigation using water and identifies the key issues that need to be resolved in order to develop an effective waterbased blast mitigation system for shipboard use in both peacetime and wartime. There are several ways in which the use of water sprays can mitigate the effects of an explosion in a ship compartment. It may: (1) break up larger droplets into finer mist (the breakup process extracts energy from the shock and weakens it); (2) directly lead to an attenuation of the shock waves produced; (3) reduce the intensity of secondary shock and pressure wave reflections from the walls and other objects in the enclosure; (4) slow down or quench the chemical reactions taking place behind the shock waves; and (5) dilute the concentration of explosive gases in the enclosure and hence prevent a secondary gas explosion or fire. In addition, the interaction depends on whether we are dealing with a shock wave, detonation or deflagration wave and the amount of water and size of the droplets that are present. Under certain circumstances the introduction of water spray could have an adverse effect by improving fuel-air mixing and accelerating flame propagation. These conditions have been identified in this report.

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