Numerical simulation of non-equilibrium characteristics of high enthalpy shock tunnel nozzle flow

The high enthalpy shock tunnel is an important ground facility for the research of hypersonic flow. However, the expansion process of the high enthalpy flow in the nozzle is a typical flow with thermo non-equilibrium and chemical non-equilibrium, and the characteristic parameters of the free stream flow are difficult to be determined by direct measurement tools. With numerical solving axisymmetric Navier-Stokes equations coupling with two temperature model, the non-equilibrium flow characteristic in a high enthalpy shock tunnel under its typical experiment conditions is studied in this paper. The rule of enthalpy to the non-equilibrium characteristics is also studied. Results show that the uniform field at the nozzle exit can reach up to 75% of the nozzle exit diameter, which can offer sufficient space for model experiment. The nozzle free stream will be frozen at about 0.4 m after the nozzle throat. With the increase of enthalpy from 8.4 to 19.5 MJ/kg, the non-equilibrium degree will increase with as enthalpy increases. At the low enthalpy, the increase will be more intense.