Aeronautics and astronautics – Aircraft sustentation – Sustaining airfoils
Patent
1985-06-13
1987-10-13
Barefoot, Galen
Aeronautics and astronautics
Aircraft sustentation
Sustaining airfoils
244200, 244130, 114 56, 114288, B64C 2306
Patent
active
046993401
ABSTRACT:
Streamwise ridges on a lifting wing intercept local flow consisting of free stream and spanwise crossflow to create a pattern of vortices over the wing and aligned with the ridge axes; the vortices act as suction pumps collecting low energy boundary layer fluid, ingesting such fluid into the core of the vortices, transporting it in the streamwise direction, and discharging it into the wake. Fresh fluid from the outer, free stream flow replaces the spent fluid withdrawn by the vortex array. This produces a favorable pressure gradient that maintains laminarity, avoiding the onset of boundary layer transition leading to turbulence. The favorable pressure gradient also suppresses separation on the back side of the wing, where the pressure gradient is normally positive and adverse. The accelerations of fluid resulting from the ridges is an order of magnitude greater than the usual streamwise accelerations produced by wing shape and friction resulting in low effective Reynolds' number dominating the boundary layer and corresponding to laminar flow. Close spacing of the ridges maximizes the interception of local flow. Each ridge is asymmetric in cross-section with a gentle ramp on its windward side and a steep bluff on its lee side to generate a standing vortex between two consecutive ridges. A slight inclination of the ridge with respect to the free stream direction at least aft of the wing's maximum thickness taps the flow in the free stream direction to augment the acceleration produced by spanwise crossflow.
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Barefoot Galen
Vehicle Research Corporation
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