Detonation and Transition to Detonation in Partially Water-Filled Pipes

Detonations and deflagration-to-detonation transition (DDT) are experimentally studied in horizontal pipes which are partially filled with water. The gas layer above the water is stoichiometric hydrogen–oxygen at 1 bar. The detonation wave produces oblique shock waves in the water, which focus at the bottom of the pipe due to the curvature of the walls. This results in peak pressures at the bottom of the pipe that are 4–6 times greater than the peak detonation pressure. Such pressure amplification is measured for water depths of 0.25, 0.5, 0.75, 0.87, and 0.92 pipe diameters. Focusing of the oblique shock waves is studied further by measuring the circumferential variation of pressure when the water depth is 0.5 pipe diameters, and reasonable agreement with theoretical modeling is found. Despite the local pressure amplification due to shock focusing, peak hoop strains decreased with increasing water depth. Failure of the detonation wave was not observed, even for water depths as high as 0.92 pipe diameters. Likewise, transition to detonation occurred for every water height.