US4706910A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Combined riblet and lebu drag reduction system
Assignee: National Aeronautics and Space Administration
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Filing: 1984-12-27
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Granted: 1987-11-17
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Expires: 2004-12-27
Abstract
Abstract The invention is a system of flow control devices which result in reduced skin friction on aerodynamic and hydrodynamic surfaces. The devices cause a breakup of large-scale disturbances in the boundary layer of the flow field. Referring to FIGS. 1 and 2, the riblet device 10 acts to reduce disturbances near the boundary layer wall by the use of longitudinal striations forming vee-shaped grooves. These grooves are dimensional on the order of the wall vortices and turbulent burst dimensions 31 depicted in FIG. 3. The large-eddy breakup device 41, depicted in FIGS. 4 and 5, is a small strip or airfoil which is suspended in the upper region of the boundary layer. Various physical mechanisms cause a disruption of the large-scale vortices. The combination of the devices of this invention result in a substantial reduction in skin friction drag.
Inventors
- 👤 Michael J. Walsh
- 👤 John B. Anders
- 👤 Jerry N. Hefner
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 04:14
CPC Classifications
B; B64; B64C; B64C21/00; B64C21/10; Y; Y02; Y02T; Y02T50/00; Y02T50/10; Y02T70/00; Y02T70/10
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
101 words
A combination of devices to reduce skin friction drag by controlling the flow characteristics of a turbulent boundary layer, such that both vertical and horizontal oscillations in the flow are damped, resulting in a substantial reduction in aerodynamic noise and retarded pressure fluctuations that lead to flutter modes, comprising: a flow surface with an attached turbulent boundary layer; riblet means on said flow surface; large-eddy break-up means suspended above, parallel to, and spanwise across the flow surface within the outer edge of the boundary layer and; means for suspending said large-eddy break-up means within the outer edge of the boundary layer.
Claim 2
Dependent Claim
101 words
A combination of devices to reduce skin friction drag by controlling the flow characteristics of a turbulent boundary layer, such that both vertical and horizontal oscillations in the flow are damped, resulting in a substantial reduction in aerodynamic noise and retarded pressure fluctuations that lead to flutter modes, comprising: a flow surface with an attached turbulent boundary layer; riblet means on said flow surface; large-eddy break-up means suspended above, parallel to, and spanwise across the flow surface within the outer edge of the boundary layer and; means for suspending said large-eddy break-up means within the outer edge of the boundary layer.
Claim 3
Dependent Claim
40 words
A combination of devices to reduce skin friction drag as in claim 1 wherein the riblet means consists of micro-geometry longitudinal grooving of the flow surface having groove depth and spacing dimensions on the order of the wall vortices dimensions.
Claim 4
Dependent Claim
42 words
A combination of devices to reduce skin frictior drag as in claim 1 wherein the large-eddy break-up device is a ribbon strip having a chord length approximately equal to the boundary layer thickness and extending spanwise across and parallel to the surface.
Claim 5
Dependent Claim
53 words
A combination of devices to reduce skin friction drag as in claim 1 wherein the large-eddy breakup devices are flat strips with a chord length between 75 and 150 percent of the boundary layer thickness and suspended between 50 and 80 percent of boundary layer thickness above and parallel to the flow surface.
Claim 6
Dependent Claim
21 words
A combination of devices to reduce skin friction drag as in claim 1 wherein the flow surface is an aerodynamic wing.
Claim 7
Dependent Claim
21 words
A combination of devices to reduce skin friction drag as in claim 1 wherein the flow surface is an aerodynamic stabilizer.
Claim 8
Dependent Claim
21 words
A combination of devices to reduce skin friction drag as in claim 1 wherein the flow surface is an aerodynamic fin.
Claim 9
Dependent Claim
21 words
A combination of devices to reduce skin friction drag as in claim 1 wherein the flow surface is a boat hull.
Claim 10
Dependent Claim
21 words
A combination of devices to reduce skin friction drag as in claim 1 wherein the flow surface is a submarine hull.
Claim 11
Dependent Claim
21 words
A combination of devices to reduce skin friction drag as in claim 1 wherein the flow surface is an aircraft fuselage.
Claim 12
Dependent Claim
25 words
A combination of devices to reduce skin friction drag as in claim 1 wherein the flow surface is the body of a ground transportation vehicle.
Claim 13
Dependent Claim
26 words
A combination of devices to reduce skin friction drag as in claim 1 wherein the flow surface is the internal surface of a fluid flow duct.
References Cited (Backward Citations)
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FR1036691A
Cited
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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) | 1990-11-16 | 1991-05-18 | 1991-11-17 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1994-11-16 | 1995-05-18 | 1995-11-17 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1998-11-16 | 1999-05-18 | 1999-11-17 | $7700.00 | Window Closed / Lapsed |