Investigations of transonic diffusers. (1st report Behavior of a shock wave in a two-dimensional circular diffuser)

Abstract

The behavior of shock waves in a two-dimensional transonic circular diffuser has been experimentally investigated by a schlieren optical method and by pressure measurements. When the overall pressure ratio of the diffuser, φ, increases, a few weak shock waves appear near the throat section before the flow is completely choked at the throat. These weak shocks are not stable but fluctuate in the channel, and the pressure at the throat p* increases with an increasing φ, although it is not in proportion to φ. when the flow is completely choked, these weak shocks coalesce into a single normal shock, and p* increases in proportion to φ. The behavior of the shock waves in diffusers with different geometries can be plotted on a single curve in an x/√(h*R)-φ plane if the position of the shock from the diffuser throat x is non-dimensionalized by the characteristic length √(h*R), where h* and R are the throat height and the radius of curvature of the diffuser, respectively.