INVESTIGATION OF THERMAL NON-EQUILIBRIUM EFFECTS IN RAPID FLOW EXPANSIONS
Abstract
The present activity deals with the internal energy excitation of molecular gases in high-speed flow expansions, as encountered in the nozzle of supersonic and hypersonic wind tunnels. The flow characterization in these facilities proved to be challenging and anomalies have often been blamed onto non-equilibrium phenomena. Emphasis is placed on flow expansions involving excited nitrogen molecules. We suggest an innovative experimental approach to narrow down the origin of the discrepancies. Experiments will be performed in the VKI Longshot hypersonic tunnel using contoured and conical nozzles. In this wind tunnel, experiments regularly use pure nitrogen as a test gas, i.e. a diatomic molecule subject to thermal non-equilibrium effects. Earlier investigations revealed free-stream static pressure larger than expected with respect to theory, potentially attributable to thermal non-equilibrium effects, yet without definite proof. The relevance of such an hypothesis will be evaluated by switching to a pure monatomic gas (helium), hence preventing thermal non-equilibrium effects from taking place. Flow characterization will be performed both pure nitrogen and pure helium environments, using intrusive and non-intrusive methods.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Aug 11, 2021
- Source ID
- FA86552017024
Entities
People
- Olivier Chazot
Organizations
- Air Force Office of Scientific Research
- United States Air Force
- von Kármán Institute for Fluid Dynamics