High Enthalpy Flow Charcteristics in Arc Heated Facilities

Abstract

The interpretation of results obtained in ground test facilities needs a detailed knowledge of the flow field. In cold facilities this flow characterisation is predominantly done by classical measurement techniques. Due to the severe flow conditions in high enthalpy facilities most of the classical techniques are not applicable and flow characterisation is only possible as a combined effort of classical and sophisticated measurement techniques and numerical tools. All parameters, which are not accessible to measurement, are characterised by computation. But even for computation the high enthalpy flow environment is challenging. Therefore a combined application of both ground testing facilities with sophisticated measurement techniques and numerical tools is necessary to cover all physical processes around a hypersonic vehicle. In arc heated facilities shortly after the nozzle throat the flow is in non-equilibrium and becomes almost frozen in the free stream. Depending on the nozzle configuration the rotational/translational temperature drops to values below 500 K. Vibrational temperatures of the species could be significantly higher. Over the shock the translational/rotational temperature jumps to a level, which is comparable to the total temperature in the reservoir. Vibrational temperatures and the chemistry relax in the shock layer in particular in the boundary layer.