Experimental characterization for hypersonic testing

The preliminary experimental characterization of the flow field developing in the test section of a small high enthalpy arc-heated Mach 6 tunnel has been carried out in terms of Mach number and local flow velocity angle. Measurements have mainly been obtained in cold flow conditions (no arc), though a limited number of tests has also been performed in hot flow conditions (Ttot=1800 K). To this purpose Pitot and yawmeter probes have been employed: in particular a theoretical model for using uncalibrated conical yawmeters in hypersonic flow has been developed. Total temperature measurements could not be obtained with the necessary accuracy due to problems of response time and survivability of thermocouples. The test campaign is presently underway and will include total temperature measurements performed by means of a fast-response total temperature probe based on transient thin-film heat flux gauge technology. List of Symbols A nozzle area h heat transfer coefficient k Newtonian coefficient M Mach number n local surface normal vector p pressure &q heat flux r nozzle radius R gas constant (288 J kg-1 K-1 for air) T temperature V velocity α,β local velocity vector angles χ Mach unsteadiness factor γ specific heat ratio ρ density θ angle between undisturbed flow and local surface normal Θ vibrational excitation temperature constan