Choking Phenomena of Flows in a Shock Tube

Abstract

If the flow area of a duct is reduced beyond a limiting value, the flow will be choked and, after a transient period of wave propagation, it will become steady and the flow rate will be decreased. At present, however, the choking phenomenon is not well understood. In this paper, the limiting conditions and the strength of a shock wave which propagates upstream when choking occurs are calculated, assuming that the flow is one-dimensional. Next, the transient flows around six kinds of wedges which were set in the low pressure channel of a shock tube were observed optically both by the schlieren method and a Mach-Zehnder interferometer. As the results, the choking process of the flow and the effect of the choking on the shape and behavior of the reflected shock wave were clarified. When the flow is choked at the wedge section, the experimental results of the velocity of the reflected shock wave agree well with the values calculated by the present one-dimensional method.