In order to obtain the characteristics of the flow field structure changes during the starting progress of the hypersonic wind tunnel

two-dimensional axisymmetric model was used to study the flow field characteristics of the nozzle section

test section and diffuser section of the Φ05 m high speed wind tunnel. The governing equations were the conservational Navier-Stokes equations

which described viscous

compressible and unsteady flows. The establishment process of flow field at test section Mach number 5

10 was compared

and the results showed that the boundary layer in the nozzle was very thick

and the complex shock structure was formed by the interaction of shock wave and boundary layer. When test section Mach number was 5

a positive shock wave was formed in the nozzle section. When the test section Mach number was 10

a shock wave string was formed from the nozzle section. The starting pressure ratio was lower than that calculated according to the positive shock theory. The starting speed of the shock wave string was slower than that of the positive shock

but its stability was better than that of the positive shock. During the starting process

the flow underexpanded excessively

and the instantaneous Mach number of the wave front was much larger than the design Mach number of the nozzle. The free jet at the exit of the nozzle and the collector played a complex role. The overfall of the collector played a key role in establishing a stable flow in the test section.