Explosion mitigation by metal grid with water curtain

Abstract

This paper examines blast mitigation based on geometric means, namely a perforated plate or a chain mail, with or without a water film cover. This method may be used for the protection of structures, and its effectiveness and limitations were assessed. First, a shock tube was used to visualize the interaction of a blast wave profile with a metallic grid or with a metallic grid covered by a layer of water. Secondly, free-field air blast experiments were performed in order to evaluate the protection system under real conditions. Three types of grids were tested. The first was a metallic plate having small round holes, the second had large round holes, and the third had square holes. A chain mail made of steel rings was also tested. The porosity of the grids ranged from 48 to 69%. In case of a collision between a shock wave and a grid, it was observed that one part of the incident shock wave was reflected by the plate. The remaining part was transmitted through the plate. The overpressure and the impulse downstream from the grid were reduced, and the reduction increased when the porosity decreased. When a film of water covered the grid, it was observed that the water film disintegrated into droplets long after the passage of the blast wave. Filling the holes with water enhanced the overpressure and impulse reduction as it contributed to the reflection of the shock wave.