Effect of Gas Injection on Transition in Hypervelocity Boundary Layers
Abstract
A novel method to delay transition in hypervelocity flows in air over slender bodies by injecting CO2 into the boundary layer is presented. The dominant transition mechanism in hypersonic flow is the inviscid second (Mack) mode, which is associated with acoustic disturbances which are trapped and amplified inside the boundary layer [8]. In dissociated CO2-rich flows, nonequilibrium molecular vibration damps the acoustic instability, and for the high-temperature, high-pressure conditions associated with hypervelocity flows, the effect is most pronounced in the frequency bands amplified by the second mode [3]. Experimental data were obtained in Caltech's T5 reflected shock tunnel. The experimental model was a 5 degree half-angle sharp cone instrumented with 80 thermocouples, providing heat transfer measurements from which transition locations were from turbulent intermittency based upon laminar and turbulent heat flux correlations. An appropriate injector was designed and fabricated, and the efficacy of injecting CO2 in delaying transition was gauged at various mass flow rates, and compared with both no injection and chemically inert Argon injection cases. Argon was chosen for its similar density to CO2. At an enthalpy of approximately 10 MJ/kg (Eckert's reference temperature Tau_= 2550 K), transition delays in terms of Reynolds number were documented. For Argon injection cases at similar mass flow rates, transition is promoted.
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 13, 2011
- Accession Number
- ADA554868
Entities
People
- Graham Candler
- H. G. Hornung
- Ivett Leyva
- Joseph E. Shepherd
- Joseph S. Jewell
- Nicholaus J. Parziale
- Ross Wagnild
Organizations
- Air Force Research Laboratory