Accession Number : AD0865396

Title :   Refraction of Underwater Explosion Shock Waves: A Method for Prediction of Pressures at Caustics,

Corporate Author : NAVAL ORDNANCE LAB WHITE OAK MD

Personal Author(s) : Blatstein, Ira M.

Report Date : 16 JAN 1970

Pagination or Media Count : 51

Abstract : Sound velocity gradients in the ocean affect the long range propagation of explosive source shock waves. Pressures and decay rates significantly different from those expected in isovelocity water have been recorded. Present theories less than adequately account for these results. The report describes a method in which finite amplitude and viscous effects are used in combination with previous acoustic results to predict pressures in the region of greatest refractive focusing, the caustic. A Fourier series representation of an exponential decay is used to describe the explosive source shock wave. A WKB solution to the pressure on the caustic as a function of source frequency is modified into an amplification factor that is applied to the components of the Fourier series. The pulse is then reconstructed and the pressure history on the caustic is determined. Calculations are made for two cases, long range propagation to a convergence zone in the ocean and propagation in a flooded quarry. For both cases the calculated peak pressure on the caustic is in good agreement with the experimental results. Furthermore, for the ocean case the calculations agree with experimental results for a considerable time after the peak pressure. (Author)

Descriptors :   (*UNDERWATER EXPLOSIONS, NUCLEAR EXPLOSIONS), (*SHOCK WAVES, REFRACTION), PRESSURE, MATHEMATICAL PREDICTION, ACOUSTICS.

Subject Categories : Explosions

Distribution Statement : APPROVED FOR PUBLIC RELEASE