Abstract: In order to obtain the influence of nozzle size on the test flowfield and the heat flux on the model surface in an arc heated wind tunnel, the numerical simulation method is used to simulate and analyze the high enthalpy flowfield of the spherical cylinder calibration model with different sizes of conical nozzles for specific test parameters. The comparison of the flowfield characteristics and the heat flux on the model surface reveals that, under the condition of simulating enthalpy and stagnation point heat flux, the nozzle with small exit size requires lower arc heating power, and the ratio of airflow energy transferred to aerodynamic heat per unit section is lower. At different nozzle exit sizes, the thermodynamic nonequilibrium degree in the exit region, the mass fraction of oxygen atom after shock wave, the pressure in the region near the stagnation point, and the proportion of conduction heat flux and diffusion heat flux are all approximate, while with any sizes of nozzles their differences between the ground experiment and the flight are obvious. The difference between the inflow velocity, the stand off distance of shock wave and the translational temperature on the stagnation line are obvious. The larger the nozzle exit size is, the more similar they are to the flight condition.

Key words: Nozzle size, Arc heated wind tunnel, High enthalpy flowfield, Numerical simulation