Experimental study on the pressure characteristics of an underwater-detonation gas jet

Abstract

Pressure evolution in the process of an underwater-detonation gas jet is experimentally researched in this study. The pressure-test experimental system is established to analyze the propagation laws of shock waves and the morphological changes of bubble pulsation. The results show that the peak pressure attenuation of the shock wave gradually slows down as the propagation distance increases. Owing to the blockage of water, a high-pressure zone is formed near the tube exit (HPZ-NE). The shock wave continues to propagate downstream after separating from the HPZ-NE, with a high-pressure zone behind the wave (HPZ-BW). The HPZ-NE has a longer duration (approximately 3.7 ms) and higher initial pressure than the HPZ-BW, and its position does not move with the shock wave. After propagation of the shock wave, the gas jet in the detonation tube continuously penetrates the water, leading to the formation of a bubble. The bubble develops in an approximate spherical shape during the first pulsation period, which is divided into four stages: rapid expansion, slow expansion, slow contraction, and rapid contraction. The expansion and contraction processes account for half of the pulsation duration, respectively. The inertia and the pressure difference alternately become the main factors of morphological changes. When the bubble contracts to the minimum volume, a new shock wave is formed by the centroid. The bubble experiences several pulsation periods in the subsequent development, accompanied by a process whereby the centroid gradually moves away from the tube exit.