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Flight Experiments on Swept-Wing Roughness Receptivity: Validation Data for Modeling and Computations
Final rept. 1 Jun 2008-31 Dec 2009
TEXAS A AND M UNIV COLLEGE STATION DEPT OF AEROSPACE ENGINEERING
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Micron-sized, spanwise-periodic Discrete Roughness Elements DREs were applied to the leading edge of a 30-degree swept-wing. The test article was attached vertically to the port wing of a Cessna O-2A aircraft and operated at a chord Reynolds number of 6.5 to 7.5 million. With a polished leading edge, 80 laminar flow was observed corresponding to N-factors greater than 12. Critically space DREs were applied a the leading edge to excite the crossflow instability and move transition forward. In this case, calibrated, multi-element hotfilm sensors were used to measure disturbance wall shear stress. The roughness height was varied from 0 to 50 microns both in the positive bumps and negative dimples sense. Thus, the disturbance amplitude variations were determined as a function of modulated DRE heights.
APPROVED FOR PUBLIC RELEASE