Aeronautics and astronautics – Aircraft structure – Details
Reexamination Certificate
2002-09-06
2004-04-06
Barefoot, Galen L. (Department: 3644)
Aeronautics and astronautics
Aircraft structure
Details
C244S199100
Reexamination Certificate
active
06715717
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to manipulation of fluid flow characteristics of airplane fuselage afterbodies, and more specifically to vortex controllers and method therefor designed to manipulate and control surrounding flow and thus reduce afterbody drag due to flow separation and drag-producing trailing vortices. The present invention is particularly suitable for, although not strictly limited to, application to upswept fuselage afterbodies characteristic of aft-loading freight/cargo aircraft such as the C-13.
BACKGROUND OF THE INVENTION
Typically, the design configuration of freight transport aircraft is substantially contingent upon loading and airdrop considerations, fuel economy consideration, and other optimal operational requirements. The result of such design dependencies generally yields a cargo aircraft possessing an upswept afterbody. As such, when subjected to the fluid flow field, such aircraft experience a crossflow on their afterbody due to wing downwash, resulting in increased flow separation on the undersurface of the afterbody. The resulting flow separation imparts a substantial amount of drag upon the afterbody and thus, reduces the overall performance of the aircraft through the flow field.
Although many attempts have been made to reduce afterbody drag via vortex generator devices attached to the upswept fuselage afterbody of the aircraft, such devices have proven effective on isolated fuselage bodies only, and have neglected to contemplate afterbody drag experienced by wing/body combinations. Strakes of various shapes and sizes attached to the afterbody have also been utilized in attempts to reduce afterbody drag, but have, however, been only marginally successful in drag reduction and local flow redirection due to wing downwash.
In general, most attempts to reduce drag experienced by sharply upswept afterbodies have proven unsuccessful due to the lack of appreciation of crossflow on the afterbody as a result of wing downwash, wherein the crossflow greatly exacerbates flow separation along the undersurface of the upswept afterbody and thus, increases afterbody drag.
Therefore, it is readily apparent that there is a need for vortex controllers that induce a series of longitudinal vortices that entrain high energy flow along the undersurface of the afterbody to prevent undersurface flow separation, thereby reducing overall afterbody drag.
BRIEF SUMMARY OF THE INVENTION
Briefly described, in a preferred embodiment, the present invention overcomes the above-mentioned disadvantages, and meets the recognized need for such a method and device by providing vortex controllers that induce a series of powerful longitudinal vortices that entrain high energy flow along the undersurface of the afterbody to reenergize the fuselage boundary layer and thus prevent undersurface flow separation, thereby reducing overall afterbody drag.
According to its major aspects and broadly stated, the present invention in its preferred form are vortex controllers in the form of fin-like projections strategically placed, wherein cross section centerlines are essentially normal to the local fuselage.
More specifically, the present invention is a plurality of substantially parallel vortex controllers in the form of fin-like projections each having a generally triangular-shaped cross-section, each vortex controller is preferably strategically placed, wherein cross section centerlines are essentially normal to the local fuselage. Each vortex controller is preferably positioned on the fuselage afterbody to ensure flow reattachment along the length of the afterbody. Each vortex controller is further preferably positioned and designed to ensure that the merging of each of the induced longitudinal vortices produced by each of the vortex controllers will create a stable single combined/merged powerful vortex along each side of the afterbody. The vortices along each side of the fuselage afterbody preferably reenergize the fuselage boundary layer and thus prevent local undersurface flow separation, thereby reducing overall afterbody drag.
A feature and advantage of the present invention is its ability to provide a method to reduce aircraft afterbody drag.
A feature and advantage of the present invention is its ability to provide a method to reduce the afterbody drag experienced by aircraft having an upswept fuselage afterbody.
A feature and advantage of the present invention is its ability to be applied to pre-existing aircraft.
A feature and advantage of the present invention is its ability to be integrally formed with an aircraft afterbody during manufacture of the same.
A feature and advantage of the present invention is its ability to provide a method and apparatus to create small powerful vortices that flow proximal to the afterbody surface and entrain flow into areas typically subjected to flow separation, thereby reducing and/or eliminating the same.
A feature and advantage of the present invention is its ability to provide a method and apparatus to entrain high-energy airflow and redirect such airflow along the undersurface of an upswept fuselage afterbody and thereby reenergize the fuselage boundary layer, prevent local undersurface flow separation and reduce overall afterbody drag.
A feature and advantage of the present invention is its ability to provide a method to combine a plurality of induced longitudinal vortices to produce a single powerful merged vortex along each side of an upswept fuselage, wherein the merged vortices remain proximal to the outer edges of the undersurface of an upswept fuselage afterbody, thus eliminating boundary layer separation from the undersurface between the merged vortices.
A feature and advantage of the present invention is its ability to be combined in any number, size, shape and angle of attack to effectuate any desirable induced vortex of appropriate strength to control flow separation and reduce afterbody drag associated with any style, shape and/or design of aircraft afterbody.
A feature and advantage of the present invention is its effective and strategic design, placement and positioning of the vortex controllers in contemplation of wing downwash and the resulting crossflow on the afterbody.
A feature and advantage of the present invention is its contemplation of afterbody streamlines in the effective and strategic design, placement, positioning and/or alignment of the vortex controllers.
These and other objects, features and advantages of the present invention will become more apparent to one skilled in the art from the following description and claims when read in light of the accompanying drawings.
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The Aviation History On-Line Museum, “www.aviation-history.com/theory/lam-flow.htm”.
Dixon Charles J.
Hughes Arthur C.
Barefoot Galen L.
Myers Joel D.
Myers & Kaplan LLC
Patel Ashish D.
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