Serrated trailing edges for improving lift and drag characteristics of lifting surfaces

• US 5,088,665 A
• Filed: 10/31/1989
• Issued: 02/18/1992
• Est. Priority Date: 10/31/1989
• Status: Expired due to Fees

• Current Assignee: The United States of America As Represented By The Secretary of Agriculture
• Original Assignee: United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration
• Inventors: Bushnell, Dennis M., Vijgen, Paul M. H. W., Holmes, Bruce J., Howard, Floyd G.
• Primary Examiner(s): Peters, Jr., Joseph F.
• Assistant Examiner(s): BIDWELL, ANNE
• Application Number:
  US07/429,516
• Time in Patent Office: 840 Days
• Field of Search: 244/198, 244/200, 244/212, 244/215
• US Class Current: 244/200
• CPC Class Codes: B64C 2003/147 comprising trailing edges of particular shape
• CPC Class Codes: B64C 23/06 by generating vortices
• CPC Class Codes: F03D 1/0675 of the blades
• CPC Class Codes: F05B 2240/301 Cross-section characteristics
• CPC Class Codes: F05B 2250/183 zigzag
• CPC Class Codes: Y02E 10/72 Wind turbines with rotation axis in wind direction
• CPC Class Codes: Y02T 50/10 Drag reduction

Abstract

An improvement in the lift and drag characteristics of a lifting surface is achieved by attaching a serrated panel to the trailing edge of the lifting surface. The serrations may have a saw-tooth configuration, with a 60° included angle between adjacent serrations. The serrations may vary in shape and size over the span-wise length of the lifting surface, and may be positioned at fixed or adjustable deflections relative to the chord of the lifting surface.

Claims

1. An apparatus for improving lift and drag characteristics of a lifting surface in a fluid flow having a span, a leading edge, a trailing edge, and a chord, comprising:

a serrated panel having an upper and a lower surface and a plurality of span-wise, periodic indentions; and

a pivotal connecting means for connecting the serrated panel to the trailing edge of the lifting surface such that the serrated panel extends from the trailing edge into the fluid flow and both the upper and lower surfaces of the serrated indentions remain in contact with the fluid.

2. An apparatus according to claim 1, wherein the serrated panel has a range of pivotal movement of substantially 90°

.

3. An apparatus according to claim 2, wherein the serrated panel is adjustably positioned coplanar with the chord at low angles of attack for drag reduction, deflected relative to the chord for increased lift and decreased drag at relatively low to moderate angles of attack, and deflected perpendicularly downward relative to the chord for maximum lift.

4. An apparatus for improving lift and drag characteristics of a lifting surface having a span, a leading edge, a trailing edge, and a chord, comprising:

a serrated panel having a plurality of span-wise, periodic indentions, wherein the indentations extend over a full length of the span; and

a pivotal connecting means for connecting the serrated panel to the trailing edge of the lifting surface.

5. An apparatus for improving lift and drag characteristics of a lifting surface in a fluid flow having a span, a leading edge, a trailing edge, and a chord, comprising:

a serrated panel having an upper and a lower surface and a plurality of span-wise, periodic indentions; and

means for connecting the serrated panel to the trailing edge of the lifting surface such that the serrated panel extends from the trailing edge into the fluid flow and both the upper and lower surface of the serrated indentions remain in contact with the fluid;

wherein the indentions extend over a partial length of the span.

6. An apparatus for improving lift and drag characteristics of a lifting surface in a fluid flow having a span, a leading edge, a trailing edge, and a chord, comprising:

a serrated panel having an upper and a lower surface and a plurality of span-wise, periodic indentions; and

means for connecting the serrated panel to the trailing edge of the lifting surface such that the serrated panel extends from the trailing edge into the fluid flow and both the upper and lower surfaces of the serrated indentions remain in contact with the fluid;

wherein the indentions have a saw-tooth configuration forming a plurality of serrations.

7. An apparatus according to claim 6, wherein the plurality of serrations are formed by adjacent teeth at 60°

included angles.

8. An apparatus for improving lift and drag characteristics of a lifting surface in a fluid flow having a span, a leading edge, a trailing edge, and a chord, comprising:

a serrated panel having an upper and a lower surface and a plurality of span-wise, periodic indentions; and

means for connecting the serrated panel to the trailing edge of the lifting surface such that the serrated panel extends from the trailing edge into the fluid flow and both the upper and lower surfaces of the serrated indentions remain in contact with the fluid;

wherein the plurality of indentions have a thickness less than or equal to about 0.1% of the chord.

9. An apparatus for improving lift and drag characteristics of a lifting surface having a span, a leading edge, a trailing edge, and a chord, comprising:

a serrated panel having a plurality of span-wise, periodic indentions;

means for connecting the serrated panel to the trailing edge of the lifting surface;

wherein the indentions have a saw-tooth configuration forming a plurality of serrations; and

wherein the serrations have a depth, shape and thickness which varies over the span of the lifting surface.

10. An apparatus for improving lift and drag characteristics of a lifting surface having a span, a leading edge, a trailing edge, and a chord, comprising:

a serrated panel having a plurality of span-wise, periodic indentions, wherein the indentions are a continuous series of concave or convex circular projections; and

a pivotal connecting means for connecting the serrated panel to the trailing edge of the lifting surface.

11. An apparatus according to claim 10, wherein the serrations are symmetrically disposed along the trailing edge.

12. An apparatus according to claim 10, wherein the serrations are asymmetrically disposed along the trailing edge.

13. An apparatus according to claim 10, wherein the serrations are semi-circularly shaped.

14. An apparatus according to claim 10, wherein the serrations are quarter-circularly shaped.

15. An apparatus for improving lift and drag characteristics of a lifting surface having a span, a wing-flap trailing edge, and a flap-slot trailing edge, comprising:

a first serrated panel having a plurality of span-wise, periodic indentations;

first connecting means for connecting the first serrated panel to the wing-flap trailing edge;

a second serrated panel having a plurality of span-wise, period indentations; and

second connecting means for connecting the second serrated panel to the flap-slot trailing edge.

16. A lift generating member according to claim 15, wherein the serrations are integrally formed in the trailing edge.

17. An apparatus according to claim 15, wherein the wing flap trailing edge is located ahead of the lifting surface.

18. A member for generating lift in a fluid flow comprising:

a leading edge;

a trailing edge;

a lifting surface between the leading edge and the trailing edge; and

a plurality of serrations formed at the trailing edge such that the serrations extend from the trailing edge into the fluid flow and all surfaces of the serrations remain in contact with the fluid.

19. An apparatus for improving lift and drag characteristics of a lifting surface having a span, a leading edge, a trailing edge, and a chord, comprising:

a serrated panel having a plurality of span-wise, periodic indentions;

wherein the serrated panel is rigidly connected to the trailing edge of the lifting surface at a fixed position between a coplanar and perpendicular orientation; and

wherein the indentions are continuous series of concave or convex circular projections.