On the Impact of Injection Schemes on Transition in Hypersonic Boundary Layers
AIR FORCE RESEARCH LAB EDWARDS AFB CA PROPULSION DIRECTORATE
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Three geometries are explored for injecting CO2 into the boundary layer of a sharp five degree half-angle cone. The impact of the injection geometry, namely discrete injection holes or a porous conical section, on tripping the boundary layer is examined, both with and without injected flow. The experiments are conducted at Caltechs T5 reflected shock tunnel. Two different air free-stream conditions are explored. For the discrete-hole injectors, the diameter for the injection holes is 0.75 mm nominally and the length to diameter ratio is about 30. One injector has a single row of holes and the other has four rows. With the 4-row geometry fully turbulent heat transfer values are measured within four centimeters of the last injection row for both free-stream conditions. The 1-row injector results on a reduction of 50 in the transition Reynolds number. The porous injector does not move the transition Reynolds number upstream by itself with no injection flow.
- Numerical Mathematics
- Fluid Mechanics