Patent US2799918A successfully refreshed from Google Patents.
US4863121A
Expired / Lapsed
US
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Boundary layer devices
Assignee: Rolls Royce PLC
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Filing: 1988-02-19
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Granted: 1989-09-05
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Expires: 2008-02-19
Abstract
Abstract An aerodynamic or hydrodynamic surface is provided with so-called "riblets" for reducing drag by modification of the turbulent boundary layer. The riblets comprise flow-aligned elongate projections of small height. In order to increase their effectiveness in reducing drag, just those parts of the riblets which extend above the height of the virtual surface--established by the riblets themselves due to their displacing the turbulent motion away from the real surface--exhibit an abrupt transition to a cusp-shaped profile which more effectively promotes very small scale flow-aligned vortices which drain energy from the larger drag-inducing low speed flow-aligned vortices or "streaks" in the boundary layer.
Inventors
- 👤 Anthony M. Savill
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 01:48
CPC Classifications
B; B64; B64C; B64C21/00; B64C21/10; B63; B63B; B63B1/00; B63B1/32; B63B1/34; B64C2230/00; B64C2230/26; Y; Y02; Y02T; Y02T50/00; Y02T50/10; Y02T70/00; Y02T70/10
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
164 words
An aerodynamic or hydrodynamic wall surface adapted to modify a turbulent fluid flow boundary layer on said surface, said surface being provided with a series of elongate projections for alignment with the direction of fluid flow relative to said surface, at least some of said projections having side faces which intermediate their heights have a region at a lesser steepness than adjacent regions above and below said region, each said region of lesser steepness forming a lower part of a concave profile peak on an associated projection, wherein said adjacent region below said region of lesser steepness has a transition to said region of lesser steepness near a virtual wall height position, said virtual wall height position being determined for a predetermined fluid flow regime, by displacement of the boundary layer turbulent flow away from said wall surface by said projections; each concave profile peak on an associated projection having a height greater than about three and three quarter wall units above said transition.
Claim 2
Dependent Claim
164 words
An aerodynamic or hydrodynamic wall surface adapted to modify a turbulent fluid flow boundary layer on said surface, said surface being provided with a series of elongate projections for alignment with the direction of fluid flow relative to said surface, at least some of said projections having side faces which intermediate their heights have a region at a lesser steepness than adjacent regions above and below said region, each said region of lesser steepness forming a lower part of a concave profile peak on an associated projection, wherein said adjacent region below said region of lesser steepness has a transition to said region of lesser steepness near a virtual wall height position, said virtual wall height position being determined for a predetermined fluid flow regime, by displacement of the boundary layer turbulent flow away from said wall surface by said projections; each concave profile peak on an associated projection having a height greater than about three and three quarter wall units above said transition.
Claim 3
Dependent Claim
47 words
A wall surface according to claim 1 wherein said series of projections comprise a plurality of higher projections between successive ones of which there is a plurality of lower projections, at least said higher projections having said concave profile peaks extending from said regions of lesser steepness.
Claim 4
Dependent Claim
45 words
A wall surface according to claim 1 wherein said projections are disposed in a repeated spanwise pattern in which adjacent projections of said pattern project to different heights, at least the highest projections having said concave profile peaks extending from said regions of lesser steepness.
Claim 5
Dependent Claim
30 words
A wall surface according to claim 2 or claim 3 wherein there are both higher and lower projections with said concave profile peaks extending from said regions of lesser steepness.
Claim 6
Dependent Claim
32 words
A wall surface according to claim 4 wherein said regions of lesser steepness are disposed at heights above said wall surface which differ in dependence upon the heights of said associated projections.
Claim 7
Dependent Claim
23 words
A wall surface according to claim 4 wherein projections of different heights have said regions of lesser steepness disposed at a common height.
Claim 8
Dependent Claim
171 words
An aerodynamic or hydrodynamic wall surface adapted to modify a turbulent fluid flow boundary layer on said surface, said surface being provided with a series of elongate projections for alignment with the direction of fluid flow relative to said surface, at least some of said projections having side faces which intermediate their heights have a region at a lesser steepness than adjacent regions above and below said region, each said region of lesser steepness forming a lower part of a concave profile peak on an associated projection, wherein said adjacent region below said region of lesser steepness has a transition to said region of lesser steepness near a virtual wall height position, said virtual wall height position being determined for a predetermined fluid flow regime, by displacement of the boundary layer turbulent flow away from said wall surface by said projections; said regions of lesser steepness of said projections being located at a height above said wall surface that increases with distance along said projections in said direction of fluid flow.
Claim 9
Dependent Claim
171 words
An aerodynamic or hydrodynamic wall surface adapted to modify a turbulent fluid flow boundary layer on said surface, said surface being provided with a series of elongate projections for alignment with the direction of fluid flow relative to said surface, at least some of said projections having side faces which intermediate their heights have a region at a lesser steepness than adjacent regions above and below said region, each said region of lesser steepness forming a lower part of a concave profile peak on an associated projection, wherein said adjacent region below said region of lesser steepness has a transition to said region of lesser steepness near a virtual wall height position, said virtual wall height position being determined for a predetermined fluid flow regime, by displacement of the boundary layer turbulent flow away from said wall surface by said projections; said regions of lesser steepness of said projections being located at a height above said wall surface that increases with distance along said projections in said direction of fluid flow.
Claim 10
Dependent Claim
108 words
An aerodynamic or hydrodynamic wall surface adapted to modify a turbulent fluid flow boundary layer on said surface, said surface being provided with a series of elongate projections for alignment with the direction of fluid flow relative to said surface, at least some of said projections having side faces which intermediate their heights have a region at a lesser steepness than adjacent regions above and below said region, each said region of lesser steepness forming a lower part of a concave profile peak on an associated projection, each said concave profile peak having a height on an associated projection greater than about three and three quarter wall units.
Claim 11
Dependent Claim
108 words
An aerodynamic or hydrodynamic wall surface adapted to modify a turbulent fluid flow boundary layer on said surface, said surface being provided with a series of elongate projections for alignment with the direction of fluid flow relative to said surface, at least some of said projections having side faces which intermediate their heights have a region at a lesser steepness than adjacent regions above and below said region, each said region of lesser steepness forming a lower part of a concave profile peak on an associated projection, each said concave profile peak having a height on an associated projection greater than about three and three quarter wall units.
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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) | 1992-09-04 | 1993-03-06 | 1993-09-05 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-09-04 | 1997-03-06 | 1997-09-05 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-09-04 | 2001-03-06 | 2001-09-05 | $7700.00 | Window Closed / Lapsed |