Investigation of the Starting Process of a Supersonic Wind Tunnel

Abstract

The starting process of a supersonic wind tunnel with a diffuser with contraction has been studied in detail by schlieren optical observations and pressure measurements. As the result, it has been shown that the wind tunnel starts when the flow is even sonic but not choked at the second throat. Based on this fact, the flow in the starting process has been classified into three patterns according to the area ratio of the second throat to the test section. Furthermore, the differences between the theoretical values and the experimental results of the starting pressure ratio and the minimum starting area at the second throat have been well explained, taking into consideration the fact that a normal shock wave assumed in the previous one-dimensional theory becomes a pseudo-shock wave due to the interaction with the wall boundary layer.