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US4936146A
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Method and apparatus for detecting laminar flow separation and reattachment
Assignee: National Aeronautics and Space Administration
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Filing: 1989-05-04
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Granted: 1990-06-26
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Expires: 2009-05-04
Abstract
Abstract The invention is a method and apparatus for simultaneously detecting laminar separation and reattachment of a fluid stream such as an airstream from and to the upper surface of an airfoil 22 by simultaneously sensing and comparing a plurality of output signals S, each representing the dynamic shear stress at one of an equal number of sensors 27 spaced along a straight line on the surface of the airfoil 22 that extends parallel to the airstream. The output signals S are simultaneously compared to detect the sensors across which a reversal in phase of said output signal S occurs, said detected sensors being in the region of laminar separation or reattachment.
Inventors
- 👤 John P. Stack
- 👤 Sivaramakrishnan M. Mangalam
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 13:58
CPC Classifications
G; G01; G01F; G01F1/00; G01F1/68; G01M; G01M9/00; G01M9/06; G01M9/065
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
113 words
A method of simultaneously detecting laminar separation and reattachment of an airstream to and from a surface of an airfoil comprising the steps of: simultaneously sensing the fluctuating dynamic shear stress at a plurality of sensor points spaced along a straight line on said surface; simultaneously generating a plurality of low frequency output signals representative of the fluctuating dynamic shear stress at said sensor points; and simultaneously comparing all of said low frequency output signals to detect at least two sensor points at which said output signals reverse in phase to thereby simultaneously detect the respective points of laminar separation and reattachment of said airstream to and from said surface of said airfoil.
Claim 2
Independent Claim
113 words
A method of simultaneously detecting laminar separation and reattachment of an airstream to and from a surface of an airfoil comprising the steps of: simultaneously sensing the fluctuating dynamic shear stress at a plurality of sensor points spaced along a straight line on said surface; simultaneously generating a plurality of low frequency output signals representative of the fluctuating dynamic shear stress at said sensor points; and simultaneously comparing all of said low frequency output signals to detect at least two sensor points at which said output signals reverse in phase to thereby simultaneously detect the respective points of laminar separation and reattachment of said airstream to and from said surface of said airfoil.
Claim 3
Dependent Claim
20 words
The method as defined in claim 1 wherein said straight line of sensor points extends parallel with said air stream.
Claim 4
Dependent Claim
49 words
The method of claim 2 wherein said plurality of output signals are simultaneously generated in a series of groups of output signals, the output signals in each of said respective groups being compared in seriation to detect any sensor point across which said output signal therefrom reverses in phase.
Claim 5
Dependent Claim
27 words
The method of claim 1 wherein said plurality of spaced sensor points are arranged in a plurality of straight lines spaced along the span of said airfoil.
Claim 6
Independent Claim
103 words
A method of detecting laminar separation of a fluid stream relative to a surface therein comprising the steps of: simultaneously sensing the fluctuating dynamic shear stress with a plurality of sensors spaced along a straight line on said surface; simultaneously generating a plurality of output signals from said sensors representative of the fluctuating dynamic shear stress along said straight line; and simultaneously comparing all of said output signals to detect a first point along said straight line at which said output signals reverse in phase, said first point of reversal in phase indicating a laminar separation of said fluid stream from said surface.
Claim 7
Independent Claim
103 words
A method of detecting laminar separation of a fluid stream relative to a surface therein comprising the steps of: simultaneously sensing the fluctuating dynamic shear stress with a plurality of sensors spaced along a straight line on said surface; simultaneously generating a plurality of output signals from said sensors representative of the fluctuating dynamic shear stress along said straight line; and simultaneously comparing all of said output signals to detect a first point along said straight line at which said output signals reverse in phase, said first point of reversal in phase indicating a laminar separation of said fluid stream from said surface.
Claim 8
Dependent Claim
43 words
The method of claim 5 including the step of simultaneously detecting a second point along said straight line at which said output signals reverse in phase, said second point of reversal in phase indicating a reattachment of said fluid stream to said surface.
Claim 9
Dependent Claim
19 words
The method as defined in claim 6 wherein said straight line of sensors extends parallel with said air stream.
Claim 10
Dependent Claim
54 words
The method of claim 7 wherein said plurality of output signals are simultaneously generated in a series of groups of output signals, the output signals in each of said respective groups being compared in seriation to detect any point along said straight line at which said output signals from said sensors reverses in phase.
Claim 11
Dependent Claim
26 words
The method of claim 6 wherein said plurality of spaced sensors are arranged in a plurality of straight lines spaced along the span of said airfoil.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1993-06-25 | 1993-12-25 | 1994-06-26 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1997-06-25 | 1997-12-25 | 1998-06-26 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2001-06-25 | 2001-12-25 | 2002-06-26 | $7700.00 | Window Closed / Lapsed |