Fracture in Straight Pipes Under Large Deflection Conditions—Part II: Pipe Pressures

Abstract

A finite difference hydrodynamic code was developed to determine the pressures in a dumbbell pipe configuration when a through crack in the pipe wall was permitted to run along the length. Computations were made for hot water pressurized pipes for two different situations: the crack tips were cusp shaped, restricted in maximum opening, and moved at prescribed subsonic or supersonic speeds; the crack configurations were computed by iterating with the structural code (Part I). The pressurized water computations were made with special equations of state for the two-phase flow in the channel and in the crack exit plane. Significant differences in pressure profiles were obtained for the supersonic and subsonic crack speeds. The air calculations were implemented by use of the perfect gas equations of state to evaluate the differencing system, its stability and the effects of the cross-sectional area change and sonic choking. The air computations followed the exponential pattern suggested by Kanninen’s simplified model when no channel choking downstream of the crack tip occurs.