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. For detonation cases, ignition and transition occur outside of the water-filled section. For DDT cases, ignition and transition occur over the surface of the water. Pressure and hoop strain are measured incrementally along the pipe, with pressure transducers located both above and below the water. The detonation wave produces an oblique shock train in the water, and the curvature of the pipe is seen to focus the shocks at the bottom, resulting in peak pressures that are 4–6 times higher than the peak detonation pressure. Such pressure amplification is observed for water depths of 0.25, 0.5, 0.75, 0.87, and 0.92 pipe diameters. For a water depth of 0.5 diameters, pressure is also recorded at several circumferential locations in order to measure the shock focusing phenomenon. Peak hoop strains are found to decrease with increasing water depth, and transition to detonation is seen to occur for water depths as high as 0.92 pipe diameters.

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