Real gas flow characterization in the ONERA F4 high enthalpy wind tunnel

The ONERA F4 Hot Shot wind tunnel provides hypersonic air flows at high enthalpy and high pressure total conditions. In such a wind tunnel, real gas effects are large yielding experimental difficulties to assess the test section free stream characteristics. Flow contamination was a problem for total enthalpy determination when using the first arc chamber configuration, made of copper and organic materials. This point has been dramatically improved with the new arc chamber made of carbon materials. Test section free stream knowledge is achieved by direct means involving optical techniques and by indirect means, i.e. through the numerical rebuilding of experiments on nozzle and standard model flows. The free stream flow is observed to be close to equilibrium on data like pressure or translational temperature, while nitric oxide (NO) concentration measurement is rather close to a nonequilibrium situation. The possibility to model such results is discussed. Finally, example example of force measurements on a capsule model is given to compare real gas with perfect gas results