Unsteady penetration of a gas jet into gas at rest

Abstract

A numerical investigation has been made of the unsteady exhausting of a supersonic jet that is formed by diffraction of a shock wave and leaves a circular channel and enters a medium of gas at rest. There is no rigorous description of all details of such flow. The work reported in the paper uses a model that takes into account the primary shock wave propagating in gas at rest, the contact surface, the secondary shock wave that moves in the opposite direction to the exhausting gas and matches the pressure in the unsteady rarefaction wave to the pressure behind the primary shock wave, the embedded shock near the edge of the channel, and the cylindrical surface of the exhausting jet [1]. Such a model makes it possible to determine the basic features of the flow, and also the trajectories and intensities of the shock waves, which agree well with the experiments [2], though the calculations do not take into account the viscosity of the gas and the temperature dependence of the specific heats. A study is also made of the problem obtained by cutting off the jet a certain time after it has been started by closing the channel exit with an impermeable barrier. The behaviors of the primary shock waves and the contact surfaces in these two cases are compared.