Control of Boundary Layers for Aero-optical Applications
Technical Report,15 Mar 2012,14 Mar 2015
University of Notre Dame Notre Dame United States
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This report presents results of systematic experimental studies of various passive mitigation techniques to reduce aero-optical effects caused be turbulent boundary layers. Parametric studies of Large-Eddy Break-Up devices showed that aero-optical distortions can be suppressed by 45 percent for several boundary layer thicknesses. It was shown that moderate cooling of the wall also reduces aero-optical distortions by 60 percent . A model to predict effects of non-adiabatic walls, both full and partial, over a range of subsonic and supersonic Mach numbers was developed and shown to correctly predict experimentally-observed reductions. Heating the wall allows extending the use of wavefront sensors into low subsonic speeds. Using this technique, aero-optical effects of boundary layers at low 1,700-8,000 Reynolds numbers, were investigated. Simultaneous velocity-optical measurements revealed that large-scale vortical structures are mostly responsible for aero-optical distortions and also indicated that the pressure fluctuations inside these vortical structures might be significant.
- Fluid Mechanics