When a high-speed projectile penetrates into water, a cavity is formed behind the projectile. The gas enclosed in the cavity experiences a nonequilibrium process, i.e., the gas pressure decreases as the projectile moves more deeply into water. As a result, the cavity is sealed near the free surface (surface closure) and subsequently the cavity breaks up in water (deep closure). Accompanying the break-up of the cavity, secondary shock waves appear. This is the so-called supercavitation in water entry. This paper describes an experimental investigation into the water entry phenomenon. Projectiles of 342 m/s were generated from a small-bore rifle that was fixed vertically in the experimental facility. The projectiles were fired into a windowed water tank. A shadowgraph optical observation was performed to observe the entry process of the projectile and the formation and collapse of the cavity behind the projectile. A number of interesting observations relating to the motion of the free surface, the splash, the underwater bubbly flow and so on were found. [S0098-2202(00)00204-2]
Optical Observation of the Supercavitation Induced by High-Speed Water Entry
Contributed by the Fluids Engineering and presented at the Symposium on Noninvasive Measurements in Multiphase Flows, ASME Fluids Engineering Summer Meeting, Boston, MA, June 11–15, 2000, of THE AMERICAN SOCIETY OF MECHANICAL ENGINEERS. Manuscript received by the Fluids Engineering Division January 28, 2000; revised manuscript received July 10, 2000. Associate Technical Editor: J. Katz.
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Shi, H., Itoh, M., and Takami, T. (July 10, 2000). "Optical Observation of the Supercavitation Induced by High-Speed Water Entry ." ASME. J. Fluids Eng. December 2000; 122(4): 806–810. https://doi.org/10.1115/1.1310575
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