THE EFFECTS OF VERTICAL DENSITY GRADIENT ON A SPHERICAL EXPLOSION.
CALIFORNIA UNIV BERKELEY INST OF ENGINEERING RESEARCH
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The aim of this work is to investigate the initial behavior of a spherical explosion, surrounded by a medium with a vertical density gradient. Special emphasis is given to the effects of this density gradient on the sphapes of the propagating shock wave and the contact surface the flow field in the region between these surfaces is also considered. An idealized model of a finite source explosion, namely, the sudden expansion of a sphere of highly compressed gas initially at rest, is considered in the present analysis. The solutions show that conditions in the expansion zone are not affected by the non-uniformity of the surrounding medium at least up to the first order and the importance of the unsymmetrical effects is apparent only in the outer regions. Two cases were calculated, namely, the blast from a pressurized sphere of air in the atmosphere and an underwater explosion. The first case deals with the isothermal expansion of air released from a pressurized sphere at an altitude of 2000 feet with an initial pressure ratio of 22. For the underwater explosion, the contained sphere of gas is released from an initial pressure of 63 atmospheres at a depth of 500 feet below the ocean surface. Results in both cases show that, in general, a small density gradient in the outer medium can have a significant influence on the shape of the shock, the variation of shock strength along the shock, the shape of the gas bubble and intermediate flow field. Author