Patent US3756540A successfully refreshed from Google Patents.
US3756540A
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Minimum drag circulation profile
Assignee: United States Department of the Navy
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Filing: 1971-08-06
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Granted: 1973-09-04
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Expires: 1991-08-06
Abstract
Abstract An airfoil chord is divided into five sections, each section producing a specialized flow over its respective surface. A first section extending from the leading edge to approximately the midpoint of the chord has a convex shape and produces laminar flow. The second section adjacent the first has a straight line surface with a negative slope which produces a transition from laminar flow to a turbulent flow. The turbulent flow region is followed by a region of minimum skin friction which has a concave surface. The chord trailing edge is a coanda profile. A tangential jet slot is placed at the trailing edge to blow over and around the coanda profile preventing flow separation and moving the stagnation region aft on the wing. The under surface is cambered to reduce the flow velocity.
Inventors
- 👤 R Williams
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 17:04
CPC Classifications
B; B64; B64C; B64C3/00; B64C3/10; B64C3/14; B64C3/141; Y; Y02; Y02T; Y02T50/00; Y02T50/10
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
198 words
An airfoil comprising: a leading edge and a trailing edge; an upper surface continuous from said leading edge to a point adjacent said trailing edge and a lower surface continuous from said leading edge to said trailing edge; said upper surface including a first section for producing accelerated laminar flow, said first section being convex in relation to the chord connecting said leading edge with said trailing edge and extending from a point adjacent said leading edge to a point slightly past the middle of said chord; said upper surface including a second section for producing a constant adverse pressure gradient and turbulent flow, said second section being aft of and adjacent said first section and being described by a straight line having a negative slope with respect to said chord; and said upper surface including a third section for decelerating the flow from its peak velocity at a rate corresponding to the condition at which the turbulent boundary layer is on the verge of separation so that the skin friction drag is approximately zero, said third section being aft of and adjacent said second section and being concave with a negative slope with respect to said chord.
Claim 2
Dependent Claim
198 words
An airfoil comprising: a leading edge and a trailing edge; an upper surface continuous from said leading edge to a point adjacent said trailing edge and a lower surface continuous from said leading edge to said trailing edge; said upper surface including a first section for producing accelerated laminar flow, said first section being convex in relation to the chord connecting said leading edge with said trailing edge and extending from a point adjacent said leading edge to a point slightly past the middle of said chord; said upper surface including a second section for producing a constant adverse pressure gradient and turbulent flow, said second section being aft of and adjacent said first section and being described by a straight line having a negative slope with respect to said chord; and said upper surface including a third section for decelerating the flow from its peak velocity at a rate corresponding to the condition at which the turbulent boundary layer is on the verge of separation so that the skin friction drag is approximately zero, said third section being aft of and adjacent said second section and being concave with a negative slope with respect to said chord.
Claim 3
Dependent Claim
25 words
The airfoil of claim 1, wherein said trailing edge has a coanda profile and is separated from said third section by a blowing slot opening.
Claim 4
Dependent Claim
20 words
The airfoil of claim 2, wherein: said lower surface is cambered to decrease the flow velocity along said lower surface.
Claim 5
Dependent Claim
97 words
The airfoil of claim 2, wherein: said convex first section is shaped according to the relation eta (X) Ao+A1X+A2X2+. . . AnXn where eta is the distance of any point on said upper surface from the X axis corresponding to said chord, X is a point on the chord and the origin of the X axis is at the leading edge; and 0 <d eta /dX < Infinity and f1(X) <d2 eta /dX2 < or = 0 where f1(X) is the minimum rate of change of curvature determined by the Laminar Instability Theory for a finite disturbance.
Claim 6
Dependent Claim
52 words
The airfoil of claim 4, wherein: said straight line second section has a slope d eta /dX such that f2(X) <d eta /dX < 0 and wherein f2(X) is the minimum slope required to introduce transition determined from the relationship Vlocal/Vfreestream Mu Alpha Xm and d Mu /dX m Alpha Xm 1
Claim 7
Dependent Claim
43 words
The airfoil of claim 5, wherein: said concave third section is described by the relationship f3(X) d eta /dX <0 f4(X) d2 eta /dX2 >0 wherein f3(X) and f4(X) are complex functions determined from Turbulent Boundary Layer Theory to produce minimum skin friction.
Claim 8
Dependent Claim
94 words
The airfoil of claim 6, where: said trailing edge has a constant radius of curvature R2; said blowing slot opening and said radius of curvature are constrained by the relationship 0 < h/R2 < 0.05 0.02 <R2/C1 < or = 0.05 0<C < or = 0.2 C /2 x(Vfs)2/1100 < or = 0.05 h/R2 where h is the cross section of the slot opening, R2 is the trailing edge radius C1 is the length of said chord and C mjVj/qC1 Where Vj jet slot flow velocity q free stream dynamic pressure mj mass flux
Claim 9
Dependent Claim
63 words
The airfoil of claim 7, wherein said lower surface between said leading edge and said trailing edge is governed by Laminar Boundary Layer Theory such that d eta /dX < or = f5(X); d2 eta /dX2 < or = f6(X) where f5(X) and f6(X) are complex function which require the curvature produce a deceleration of flow along the under surface with increased pressure.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-09-03 | 1977-03-05 | 1977-09-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-09-03 | 1981-03-05 | 1981-09-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-09-03 | 1985-03-05 | 1985-09-04 | $7700.00 | Window Closed / Lapsed |