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