U.S. patent application number 12/832967 was filed with the patent office on 2011-01-13 for application of conformal sub boundary layer vortex generators to a foil or aero/ hydrodynamic surface.
Invention is credited to Peter Ireland.
Application Number | 20110006165 12/832967 |
Document ID | / |
Family ID | 43426759 |
Filed Date | 2011-01-13 |
United States Patent
Application |
20110006165 |
Kind Code |
A1 |
Ireland; Peter |
January 13, 2011 |
APPLICATION OF CONFORMAL SUB BOUNDARY LAYER VORTEX GENERATORS TO A
FOIL OR AERO/ HYDRODYNAMIC SURFACE
Abstract
A method of improving aerodynamic performance of foils by the
application of conformal, low drag vortex generators. A film of
erosion protection material or other conformal material is placed
on the foil to provide a medium for the incorporation of planform
edge vortex generators. The form edge is shaped to achieve
submerged vortex generating shapes of chevron or ogival planforms,
extending primarily chordwise on the foil surface. The vortex
generators promote improved boundary layer dynamics by mixing free
stream flow into the boundary layer while minimising separation and
fluid losses. At the trailing edge, the shape formed with the
chevrons applied apex forward, acts as a vented gurney tab series
and additionally as disruptors to the Von Karman Street wake,
delaying sheet rollup into the tip vortice.
Inventors: |
Ireland; Peter; (Wenworth
Falls, AU) |
Correspondence
Address: |
NWAMU, P.C.
360 Grand Ave, Suite 109
Oakland
CA
94610
US
|
Family ID: |
43426759 |
Appl. No.: |
12/832967 |
Filed: |
July 8, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61224481 |
Jul 10, 2009 |
|
|
|
Current U.S.
Class: |
244/200.1 |
Current CPC
Class: |
Y02T 50/162 20130101;
Y02T 50/12 20130101; Y02T 50/10 20130101; B64C 23/06 20130101; B64C
23/065 20130101; B64C 2003/147 20130101 |
Class at
Publication: |
244/200.1 |
International
Class: |
B64C 21/10 20060101
B64C021/10 |
Claims
1. An application of conformal sub boundary layer vortex generators
to a foil or aero/hydrodynamic surface for reducing drag or
improving lift or lift to drag ratios, comprising: means for
developing a pair of counter rotating streamwise vortices for the
purpose of re-energising the boundary layer, thereby improving lift
or drag or lift to drag ratios.
2. The application of conformal sub boundary layer vortex
generators to a foil or aero/hydrodynamic surface in accordance
with claim 1, wherein said means for developing a pair of counter
rotating streamwise vortices for the purpose of re-energising the
boundary layer, thereby improving lift or drag or lift to drag
ratios comprises a conformal to substrate, elastomeric, planform
for generating predominately streamwise vortices, that minimises
extent of transverse linear trailing edge, thermally stable,
chevron or triangular planform, with a planform of linear v sides,
or, with a planform of ogival sides sub boundary layer vortex
generators.
3. An application of conformal sub boundary layer vortex generators
to a foil or aero/hydrodynamic surface for reducing drag or
improving lift or lift to drag ratios, comprising: a conformal to
substrate, elastomeric, planform for generating predominately
streamwise vortices, that minimises extent of transverse linear
trailing edge, thermally stable, chevron or triangular planform,
with a planform of linear v sides, or, with a planform of ogival
sides sub boundary layer vortex generators, for developing a pair
of counter rotating streamwise vortices for the purpose of
re-energising the boundary layer, thereby improving lift or drag or
lift to drag ratios.
4. The application of conformal sub boundary layer vortex
generators to a foil or aero/hydrodynamic surface as recited in
claim 3, further comprising: an elastomeric, thermally stable
within operational limitations, bondable, erosion resistant polymer
erosion protection layer, for providing erosion protection,
integrally conformed to said sub boundary layer vortex
generators.
5. The application of conformal sub boundary layer vortex
generators to a foil or aero/hydrodynamic surface as recited in
claim 3, further comprising: an elastomeric, thermally stable,
bondable application medium, for providing a medium to embed
performance enhancing sub boundary layer vortex generators upon,
integrally constructed to said sub boundary layer vortex
generators.
6. The application of conformal sub boundary layer vortex
generators to a foil or aero/hydrodynamic surface as recited in
claim 3, further comprising: a planform of aft facing steps
preferentially angled to relative flow, fabricated in an erosion
protection material, conformal, bondable, located with abutted to a
lapjoint and with height equal to the lapjoint step v form sub
boundary layer vortex generators, for generating a pair of counter
rotating streamwise vortices that re-energise the boundary
layer.
7. The application of conformal sub boundary layer vortex
generators to a foil or aero/hydrodynamic surface as recited in
claim 3, further comprising: a sub boundary layer vortex generator
mask, for masking a planform shape that is beneficial for
developing a surface layer edge shape that promotes vorticity in
the boundary layer.
8. The application of conformal sub boundary layer vortex
generators to a foil or aero/hydrodynamic surface as recited in
claim 3, further comprising: a series of, linear penetration of
laminate, aligned parallel to flow, of a length of between 2 to 10
times the laminate height laminate substrate vents, for venting the
base of the laminate to atmosphere to mitigate bubble formation,
completely inserted to said application medium.
9. The application of conformal sub boundary layer vortex
generators to a foil or aero/hydrodynamic surface as recited in
claim 3, further comprising: a trailing edge planform that promotes
streamwise vorticity, overlaps trailing component surface lapjoint,
for join of component sections whereby streamwise vortices are
generated to re-energise the boundary layer, and reduce drag,
increase lift or improve lift/drag ratios, adhesively appended to
said v form sub boundary layer vortex generators.
10. The application of conformal sub boundary layer vortex
generators to a foil or aero/hydrodynamic surface as recited in
claim 3, further comprising: a plurality of separate, elastomeric,
conformal, sub boundary layer height, series with spacing between
chevrons of a minimum of 2 times base width, tip forward, base aft
chevron configuration, relative to the freestream flow, with base
located between 2 to zero times the height of chevron from the
trailing edge of the surface sub boundary layer trailing edge
chevron, for developing 2 counter rotating vortices proximate to
the trailing edge, and a transverse vortex across the base of the
chevron, bounded by the trailing edge surface and the aft face of
the chevron.
11. The application of conformal sub boundary layer vortex
generators to a foil or aero/hydrodynamic surface as recited in
claim 4, further comprising: a planform of aft facing steps
preferentially angled to relative flow, fabricated in an erosion
protection material, conformal, bondable, located with abutted to a
lapjoint and with height equal to the lapjoint step v form sub
boundary layer vortex generators, for generating a pair of counter
rotating streamwise vortices that re-energise the boundary layer,
adhesively appended to said lapjoint.
12. The application of conformal sub boundary layer vortex
generators to a foil or aero/hydrodynamic surface as recited in
claim 4, further comprising: a series of, linear penetration of
laminate, aligned parallel to flow, of a length of between 2 to 10
times the laminate height laminate substrate vents, for venting the
base of the laminate to atmosphere to mitigate bubble formation,
completely inserted to said application medium.
13. The application of conformal sub boundary layer vortex
generators to a foil or aero/hydrodynamic surface as recited in
claim 4, further comprising: a trailing edge planform that promotes
streamwise vorticity, overlaps trailing component surface lapjoint,
for join of component sections whereby streamwise vortices are
generated to re-energise the boundary layer, and reduce drag,
increase lift or improve lift/drag ratios, adhesively appended to
said v form sub boundary layer vortex generators.
14. The application of conformal sub boundary layer vortex
generators to a foil or aero/hydrodynamic surface as recited in
claim 4, further comprising: a plurality of separate, elastomeric,
conformal, sub boundary layer height, series with spacing between
chevrons of a minimum of 2 times base width, tip forward, base aft
chevron configuration, relative to the freestream flow, with base
located between 2 to zero times the height of chevron from the
trailing edge of the surface sub boundary layer trailing edge
chevron, for developing 2 counter rotating vortices proximate to
the trailing edge, and a transverse vortex across the base of the
chevron, bounded by the trailing edge surface and the aft face of
the chevron.
15. The application of conformal sub boundary layer vortex
generators to a foil or aero/hydrodynamic surface as recited in
claim 5, further comprising: a planform of aft facing steps
preferentially angled to relative flow, fabricated in an erosion
protection material, conformal, bondable, located with abutted to a
lapjoint and with height equal to the lapjoint step v form sub
boundary layer vortex generators, for generating a pair of counter
rotating streamwise vortices that re-energise the boundary layer,
adhesively appended to said lapjoint.
16. The application of conformal sub boundary layer vortex
generators to a foil or aero/hydrodynamic surface as recited in
claim 5, further comprising: a sub boundary layer vortex generator
mask, for masking a planform shape that is beneficial for
developing a surface layer edge shape that promotes vorticity in
the boundary layer.
17. The application of conformal sub boundary layer vortex
generators to a foil or aero/hydrodynamic surface as recited in
claim 5, further comprising: a series of, linear penetration of
laminate, aligned parallel to flow, of a length of between 2 to 10
times the laminate height laminate substrate vents, for venting the
base of the laminate to atmosphere to mitigate bubble formation,
completely inserted to said application medium.
18. The application of conformal sub boundary layer vortex
generators to a foil or aero/hydrodynamic surface as recited in
claim 5, further comprising: a trailing edge planform that promotes
streamwise vorticity, overlaps trailing component surface lapjoint,
for join of component sections whereby streamwise vortices are
generated to re-energise the boundary layer, and reduce drag,
increase lift or improve lift/drag ratios, adhesively appended to
said v form sub boundary layer vortex generators.
19. The application of conformal sub boundary layer vortex
generators to a foil or aero/hydrodynamic surface as recited in
claim 5, further comprising: a plurality of separate, elastomeric,
conformal, sub boundary layer height, series with spacing between
chevrons of a minimum of 2 times base width, tip forward, base aft
chevron configuration, relative to the freestream flow, with base
located between 2 to zero times the height of chevron from the
trailing edge of the surface sub boundary layer trailing edge
chevron, for developing 2 counter rotating vortices proximate to
the trailing edge, and a transverse vortex across the base of the
chevron, bounded by the trailing edge surface and the aft face of
the chevron.
20. The application of conformal sub boundary layer vortex
generators to a foil or aero/hydrodynamic surface as recited in
claim 6, further comprising: a sub boundary layer vortex generator
mask, for masking a planform shape that is beneficial for
developing a surface layer edge shape that promotes vorticity in
the boundary layer.
21. The application of conformal sub boundary layer vortex
generators to a foil or aero/hydrodynamic surface as recited in
claim 6, further comprising: a series of, linear penetration of
laminate, aligned parallel to flow, of a length of between 2 to 10
times the laminate height laminate substrate vents, for venting the
base of the laminate to atmosphere to mitigate bubble formation,
completely inserted to said application medium.
22. The application of conformal sub boundary layer vortex
generators to a foil or aero/hydrodynamic surface as recited in
claim 6, further comprising: a trailing edge planform that promotes
streamwise vorticity, overlaps trailing component surface lapjoint,
for join of component sections whereby streamwise vortices are
generated to re-energise the boundary layer, and reduce drag,
increase lift or improve lift/drag ratios, adhesively appended to
said v form sub boundary layer vortex generators.
23. The application of conformal sub boundary layer vortex
generators to a foil or aero/hydrodynamic surface as recited in
claim 6, further comprising: a plurality of separate, elastomeric,
conformal, sub boundary layer height, series with spacing between
chevrons of a minimum of 2 times base width, tip forward, base aft
chevron configuration, relative to the freestream flow, with base
located between 2 to zero times the height of chevron from the
trailing edge of the surface sub boundary layer trailing edge
chevron, for developing 2 counter rotating vortices proximate to
the trailing edge, and a transverse vortex across the base of the
chevron, bounded by the trailing edge surface and the aft face of
the chevron.
24. The application of conformal sub boundary layer vortex
generators to a foil or aero/hydrodynamic surface as recited in
claim 9, further comprising: a plurality of separate, elastomeric,
conformal, sub boundary layer height, series with spacing between
chevrons of a minimum of 2 times base width, tip forward, base aft
chevron configuration, relative to the freestream flow, with base
located between 2 to zero times the height of chevron from the
trailing edge of the surface sub boundary layer trailing edge
chevron, for developing 2 counter rotating vortices proximate to
the trailing edge, and a transverse vortex across the base of the
chevron, bounded by the trailing edge surface and the aft face of
the chevron.
25. The application of conformal sub boundary layer vortex
generators to a foil or aero/hydrodynamic surface as recited in
claim 11, further comprising: a sub boundary layer vortex generator
mask, for masking a planform shape that is beneficial for
developing a surface layer edge shape that promotes vorticity in
the boundary layer.
26. The application of conformal sub boundary layer vortex
generators to a foil or aero/hydrodynamic surface as recited in
claim 11, further comprising: a series of, linear penetration of
laminate, aligned parallel to flow, of a length of between 2 to 10
times the laminate height laminate substrate vents, for venting the
base of the laminate to atmosphere to mitigate bubble formation,
completely inserted to said application medium.
27. The application of conformal sub boundary layer vortex
generators to a foil or aero/hydrodynamic surface as recited in
claim 11, further comprising: a trailing edge planform that
promotes streamwise vorticity, overlaps trailing component surface
lapjoint, for join of component sections whereby streamwise
vortices are generated to re-energise the boundary layer, and
reduce drag, increase lift or improve lift/drag ratios, adhesively
appended to said v form sub boundary layer vortex generators.
28. The application of conformal sub boundary layer vortex
generators to a foil or aero/hydrodynamic surface as recited in
claim 11, further comprising: a plurality of separate, elastomeric,
conformal, sub boundary layer height, series with spacing between
chevrons of a minimum of 2 times base width, tip forward, base aft
chevron configuration, relative to the freestream flow, with base
located between 2 to zero times the height of chevron from the
trailing edge of the surface sub boundary layer trailing edge
chevron, for developing 2 counter rotating vortices proximate to
the trailing edge, and a transverse vortex across the base of the
chevron, bounded by the trailing edge surface and the aft face of
the chevron.
29. The application of conformal sub boundary layer vortex
generators to a foil or aero/hydrodynamic surface as recited in
claim 12, further comprising: a trailing edge planform that
promotes streamwise vorticity, overlaps trailing component surface
lapjoint, for join of component sections whereby streamwise
vortices are generated to re-energise the boundary layer, and
reduce drag, increase lift or improve lift/drag ratios, adhesively
appended to said v form sub boundary layer vortex generators.
30. The application of conformal sub boundary layer vortex
generators to a foil or aero/hydrodynamic surface as recited in
claim 12, further comprising: a plurality of separate, elastomeric,
conformal, sub boundary layer height, series with spacing between
chevrons of a minimum of 2 times base width, tip forward, base aft
chevron configuration, relative to the freestream flow, with base
located between 2 to zero times the height of chevron from the
trailing edge of the surface sub boundary layer trailing edge
chevron, for developing 2 counter rotating vortices proximate to
the trailing edge, and a transverse vortex across the base of the
chevron, bounded by the trailing edge surface and the aft face of
the chevron.
31. The application of conformal sub boundary layer vortex
generators to a foil or aero/hydrodynamic surface as recited in
claim 13, further comprising: a plurality of separate, elastomeric,
conformal, sub boundary layer height, series with spacing between
chevrons of a minimum of 2 times base width, tip forward, base aft
chevron configuration, relative to the freestream flow, with base
located between 2 to zero times the height of chevron from the
trailing edge of the surface sub boundary layer trailing edge
chevron, for developing 2 counter rotating vortices proximate to
the trailing edge, and a transverse vortex across the base of the
chevron, bounded by the trailing edge surface and the aft face of
the chevron.
32. The application of conformal sub boundary layer vortex
generators to a foil or aero/hydrodynamic surface as recited in
claim 15, further comprising: a series of, linear penetration of
laminate, aligned parallel to flow, of a length of between 2 to 10
times the laminate height laminate substrate vents, for venting the
base of the laminate to atmosphere to mitigate bubble formation,
completely inserted to said application medium.
33. The application of conformal sub boundary layer vortex
generators to a foil or aero/hydrodynamic surface as recited in
claim 18, further comprising: a plurality of separate, elastomeric,
conformal, sub boundary layer height, series with spacing between
chevrons of a minimum of 2 times base width, tip forward, base aft
chevron configuration, relative to the freestream flow, with base
located between 2 to zero times the height of chevron from the
trailing edge of the surface sub boundary layer trailing edge
chevron, for developing 2 counter rotating vortices proximate to
the trailing edge, and a transverse vortex across the base of the
chevron, bounded by the trailing edge surface and the aft face of
the chevron.
34. The application of conformal sub boundary layer vortex
generators to a foil or aero/hydrodynamic surface as recited in
claim 21, further comprising: a trailing edge planform that
promotes streamwise vorticity, overlaps trailing component surface
lapjoint, for join of component sections whereby streamwise
vortices are generated to re-energise the boundary layer, and
reduce drag, increase lift or improve lift/drag ratios, adhesively
appended to said v form sub boundary layer vortex generators.
35. The application of conformal sub boundary layer vortex
generators to a foil or aero/hydrodynamic surface as recited in
claim 21, further comprising: a plurality of separate, elastomeric,
conformal, sub boundary layer height, series with spacing between
chevrons of a minimum of 2 times base width, tip forward, base aft
chevron configuration, relative to the freestream flow, with base
located between 2 to zero times the height of chevron from the
trailing edge of the surface sub boundary layer trailing edge
chevron, for developing 2 counter rotating vortices proximate to
the trailing edge, and a transverse vortex across the base of the
chevron, bounded by the trailing edge surface and the aft face of
the chevron.
36. The application of conformal sub boundary layer vortex
generators to a foil or aero/hydrodynamic surface as recited in
claim 22, further comprising: a plurality of separate, elastomeric,
conformal, sub boundary layer height, series with spacing between
chevrons of a minimum of 2 times base width, tip forward, base aft
chevron configuration, relative to the freestream flow, with base
located between 2 to zero times the height of chevron from the
trailing edge of the surface sub boundary layer trailing edge
chevron, for developing 2 counter rotating vortices proximate to
the trailing edge, and a transverse vortex across the base of the
chevron, bounded by the trailing edge surface and the aft face of
the chevron.
37. The application of conformal sub boundary layer vortex
generators to a foil or aero/hydrodynamic surface as recited in
claim 26, further comprising: a trailing edge planform that
promotes streamwise vorticity, overlaps trailing component surface
lapjoint, for join of component sections whereby streamwise
vortices are generated to re-energise the boundary layer, and
reduce drag, increase lift or improve lift/drag ratios, adhesively
appended to said v form sub boundary layer vortex generators.
38. The application of conformal sub boundary layer vortex
generators to a foil or aero/hydrodynamic surface as recited in
claim 26, further comprising: a plurality of separate, elastomeric,
conformal, sub boundary layer height, series with spacing between
chevrons of a minimum of 2 times base width, tip forward, base aft
chevron configuration, relative to the freestream flow, with base
located between 2 to zero times the height of chevron from the
trailing edge of the surface sub boundary layer trailing edge
chevron, for developing 2 counter rotating vortices proximate to
the trailing edge, and a transverse vortex across the base of the
chevron, bounded by the trailing edge surface and the aft face of
the chevron.
39. The application of conformal sub boundary layer vortex
generators to a foil or aero/hydrodynamic surface as recited in
claim 27, further comprising: a plurality of separate, elastomeric,
conformal, sub boundary layer height, series with spacing between
chevrons of a minimum of 2 times base width, tip forward, base aft
chevron configuration, relative to the freestream flow, with base
located between 2 to zero times the height of chevron from the
trailing edge of the surface sub boundary layer trailing edge
chevron, for developing 2 counter rotating vortices proximate to
the trailing edge, and a transverse vortex across the base of the
chevron, bounded by the trailing edge surface and the aft face of
the chevron.
40. The application of conformal sub boundary layer vortex
generators to a foil or aero/hydrodynamic surface as recited in
claim 29, further comprising: a plurality of separate, elastomeric,
conformal, sub boundary layer height, series with spacing between
chevrons of a minimum of 2 times base width, tip forward, base aft
chevron configuration, relative to the freestream flow, with base
located between 2 to zero times the height of chevron from the
trailing edge of the surface sub boundary layer trailing edge
chevron, for developing 2 counter rotating vortices proximate to
the trailing edge, and a transverse vortex across the base of the
chevron, bounded by the trailing edge surface and the aft face of
the chevron.
41. The application of conformal sub boundary layer vortex
generators to a foil or aero/hydrodynamic surface as recited in
claim 34, further comprising: a plurality of separate, elastomeric,
conformal, sub boundary layer height, series with spacing between
chevrons of a minimum of 2 times base width, tip forward, base aft
chevron configuration, relative to the freestream flow, with base
located between 2 to zero times the height of chevron from the
trailing edge of the surface sub boundary layer trailing edge
chevron, for developing 2 counter rotating vortices proximate to
the trailing edge, and a transverse vortex across the base of the
chevron, bounded by the trailing edge surface and the aft face of
the chevron.
42. An application of conformal sub boundary layer vortex
generators to a foil or aero/hydrodynamic surface for reducing drag
or improving lift or lift to drag ratios, comprising: an
elastomeric, thermally stable within operational limitations,
bondable, erosion resistant polymer erosion protection layer, for
providing erosion protection; an elastomeric, thermally stable,
bondable application medium, for providing a medium to embed
performance enhancing sub boundary layer vortex generators upon; a
planform of aft facing steps preferentially angled to relative
flow, fabricated in an erosion protection material, conformal,
bondable, located with abutted to a lapjoint and with height equal
to the lapjoint step v form sub boundary layer vortex generators,
for generating a pair of counter rotating streamwise vortices that
re-energise the boundary layer; a conformal to substrate,
elastomeric, planform for generating predominately streamwise
vortices, that minimises extent of transverse linear trailing edge,
thermally stable, chevron or triangular planform, with a planform
of linear v sides, or, with a planform of ogival sides sub boundary
layer vortex generators, for developing a pair of counter rotating
streamwise vortices for the purpose of re-energising the boundary
layer, thereby improving lift or drag or lift to drag ratios,
integrally constructed to said application medium, and integrally
conformed to said erosion protection layer; a sub boundary layer
vortex generator mask, for masking a planform shape that is
beneficial for developing a surface layer edge shape that promotes
vorticity in the boundary layer; a series of, linear penetration of
laminate, aligned parallel to flow, of a length of between 2 to 10
times the laminate height laminate substrate vents, for venting the
base of the laminate to atmosphere to mitigate bubble formation,
completely inserted to said application medium; a trailing edge
planform that promotes streamwise vorticity, overlaps trailing
component surface lapjoint, for join of component sections whereby
streamwise vortices are generated to re-energise the boundary
layer, and reduce drag, increase lift or improve lift/drag ratios,
adhesively appended to said v form sub boundary layer vortex
generators; and a plurality of separate, elastomeric, conformal,
sub boundary layer height, series with spacing between chevrons of
a minimum of 2 times base width, tip forward, base aft chevron
configuration, relative to the freestream flow, with base located
between 2 to zero times the height of chevron from the trailing
edge of the surface sub boundary layer trailing edge chevron, for
developing 2 counter rotating vortices proximate to the trailing
edge, and a transverse vortex across the base of the chevron,
bounded by the trailing edge surface and the aft face of the
chevron.
Description
RELATED APPLICATIONS
[0001] The present application is a continuation-in-part
application of U.S. provisional patent application, Ser. No.
61224481, filed Oct. 7, 2009, for ELASTOMERIC VORTEX GENERATORS, by
Peter S. Ireland, included by reference herein and for which
benefit of the priority date is hereby claimed.
[0002] Elastomeric Vortex Generator Provisional patent, Ireland P
S, of 10 Jul. 2009. (EFS ID 5676629 Application Number 61224481
Confirmation Number 2708 Title Elastomeric Vortex Generator(s)
First Named Inventor Peter Stephen Ireland)
FIELD OF THE INVENTION
[0003] The present invention relates to the addition of low drag
fully submerged conformal vortex generators to a surface in
relative motion to a Newtonian fluid and, more particularly, to
aeronautical and marine surfaces, blades, rotors, and appendages
having a boundary layer with fluid flow across such surface.
BACKGROUND OF THE INVENTION
[0004] Performance of a foil or surface in a flow of fluid such as
air or water is critical for a system performance, affecting lift,
drag and vibration of a system.
[0005] The leading section of the foil is usually an area of
increasing thickness and results in a thin laminar boundary layer
until such point that viscous drag, surface friction or
pertuberances causes turbulence to occur in the boundary layer. The
turbulent boundary layer has characteristically higher drag than
the laminar flow region, however may also have improved stability
of flow. The development of an adverse pressure gradient results in
separation of the flow from the surface, and a further large
increase in drag occurs from this point rearwards. While a foil
section may be designed to maintain a large area of laminar
boundary layer, practical limitations of manufacture and
cleanliness generally preclude widescale laminar boundary layer
development.
[0006] Leading edges of foils on blades are subject to erosion and
can benefit from the application of a protective abradable layer.
The abradable or protective surface may be applied as an adhesive
sheet to the foil leading edge, or alternatively as a high build
polymeric material that is sprayed on or otherwise applied to the
desired leading edge area. Unfortunately, in current art, where
this is applied, this results in an alteration of the basic foil
shape aerodynamically, and causes a ridge to occur at the trailing
edge of the protective layer. The current art protection mechanisms
result in these mechanisms having a trailing edge form of an aft
facing step aerodynamically, which causes an increase in drag and
develops a transverse vortex to occur on the foil. This step/vortex
tends to disrupt the laminar boundary layer and cause early
transition to turbulent boundary layer or in extreme cases,
separation of flow.
[0007] In manufacture of rotor blades, a bond line is often found
at approximately 15-20% of the chord back from the leading edge of
the foil. This bond line is the join between the surface skins and
the extrusion used as a spar. The painted surface protecting this
bond is susceptible to being eroded and following erosion of the
paint protection it is possible for moisture to enter the bond and
result in bond failure. Such failure can be catastrophic.
[0008] Noise signature of a blade, or other foil is affected by the
vortex development in the wake of the section. Additionally, lift
and drag performance can be affected greatly by the use of trailing
edge modifiers. In practice, this performance is not attained due
to constraints of engineering a suitable mechanism.
[0009] Leading edge erosion protection has been provided
generically by application of tapes to the leading edge surface of
the foil or blade, using a polymeric material such as polyurethane,
or other elastomeric compounds.
[0010] Micro Vortex generators, microVG's, are fabricated from a
rigid material such as aluminium are used to reenergise boundary
layers. Large Eddy Breakup Units, or LEBU's are occasionally used
to adjust a boundary layer condition, and are constructed from
rigid materials. A drag modifying surface is manufactured by 3M
under the tradename "Riblet". This surface is a thin textured film,
designed to provide a reenergising of the boundary layer to reduce
surface drag.
[0011] To change acoustic signature and/or lift/drag performance,
fluting of the trailing edge of a foil or section has been
accomplished, and tabs such as lift enhancing tabs or gurney tabs
have been applied in experimentation. Fluting has been accomplished
on jet engine exhaust systems in current art.
[0012] Leading edge erosion protection films, tapes or shaped boots
result in disrupting the boundary layer in a critical area of the
foil, due to the aft facing step between the trailing edge of the
treatment and the upper surface of the foil. This results in
developing a local flow pattern which causes thickening of the
boundary layer from laminar to turbulent and causing separation of
the local flow, in both cases reducing lift and increasing drag.
Fairing of the aft edge to the surface may often exacerbate the
performance degradation as the stability of the transverse vortex
generated at the aft face of the step often has less drag than a
less abrupt face which causes irregular flow dynamics and results
in more turbulence and greater likelihood of separation of
flow.
[0013] Current boundary layer modifiers such as micro VG's and
LEBU's are rigid in structure. The material they are made from
allows limited flexure of the structure, and will not permit the
underlying surface to flex. Where there is substantial structural
flexing and the modifier extends over any length, these solutions
are unable to be used without affecting the torsional or flexing
characteristics of the underlying structure. This can result in
serious aeroelastic effects, causing structural failure or damage,
and are inherently impacted by any alternating loads, bending or
flexing resulting in material fatigue. The micro VG's, and similar
current art vortex generators are often characterised as being
"micro", however as a percentage of the boundary layer height, they
are multiples of the laminar boundary layer height in the region of
the forward chord of the blade, whereas conventional design
optimisation of micro VG's indicate that their height should be
less than the boundary layer and generally of the order of 20% or
less of the boundary layer thickness to minimise drag losses, while
maintaining effectiveness of developing streamwise vortices.
[0014] Structural mass of any addition to a foil must be considered
for the tensile loading of the foil, particularly for a blade, and
also the location on the blade relative to the chord must be
considered: weight added at the trailing edge is potentially
adverse to the dynamic stability of the foil (flutter). This may be
offset by related aerodynamic effects if those effects move the
centre of pressure rearward more than the weight addition shifts
the centre of mass of the foil section. Addition of mass to a rotor
system increases inertial loading in the feathering axis, pitching
axis, and increases radial shear loads. Therefore, minimum mass
needs to be achieved at all times.
[0015] Fluting of a section involves complex engineering, and can
result in structural problems such as material fatigue. Gurney tabs
are predominately mechanical devices, and the structure adds weight
and additionally affects torsional and bending moments of inertia
of a structure. This may cause bond or fastener failure over time
through fatigue and incompatibility of the attachment system.
SUMMARY OF THE INVENTION
[0016] In accordance with the present invention, there is provided
a film surface being an advantageously machined polymeric or
polyurethane tape element. This film is attached by a high shear
strength adhesive that permits flexure of the film for conformal
fitment to the substrate, being a wing, surface or foil such as a
rotorblade, and allows for the removal of the film after use. The
film is advantageously shaped so as to have a regular series of V
shapes on both of the transverse edges of the film. This film is
applied around the leading edge of the foil to result in these V
shapes facing away from the leading edge towards the trailing edge.
Thus the film is a method of incorporating a vortex generating
profile planform, which also minimises the extent of straight
transverse aft facing steps that exist when the film is attached
around the leading edge of a foil. The commencement and termination
of these V shapes are determined by the boundary layer
characteristics of the foil that the surface is applied to, however
in general will be applied in the region of 5% to 25% of the chord
of the foil. The sizing of the V shapes is determined by the foil
dimensions and Reynolds number, and can be optimised by numeric
analysis or by parametric testing for any foil, or surface.
[0017] When applied near the leading edge of the blade or foil, as
a vortex generator, the film is used to form a final polymeric
layer being either a performance enhancement treatment or an
erosion protection layer, with the beneficial effect of reducing
drag either comparative to existing protective treatments or
baseline, and or increasing lift, or lift to drag ratios by
promoting spanwise vortices to be generated, assisting in
reenergising the boundary layer aft of the film section. Thus, the
invention both removes or minimises the causal mechanism of the aft
facing step, thereby avoiding the adverse effects on lift and drag
associated with such a step, and further, provides a series of
conformal sub boundary layer vortex generators that enhance the
boundary layer compared to a clean baseline blade
configuration.
[0018] The v form planform is designed to achieve optimal vortice
generation, and this results generally in having both hypotenuse
attaining a relative angle to the free stream flow (being the
adjacent direction) of between 15 degrees and 25 degrees included
angle on each side of the adjacent direction. It should be noted
that in cases where a squat triangular form is produced, and the
hypotenuse to adjacent angle is large, in excess of 60 degrees,
then the resultant flow may actually be adversely affected such as
to increase drag compared to a continuous transverse aft facing
step. It is therefore critical that the shape of the vortex
generator applied acts to develop streamwise vorticity. The macro
sizing of the planform is a function of relative position on the
chord and number of vortex generators than can be applied, and
results in approximately a repeat or base width of the shapes at
0.1.times. Chord width. The height of the V is approximately
2.times. the repeat base width. Where the thickness of the
protection film is of the order of 0.2% of the chord width, the sub
boundary layer vortex generator achieves streamwise vorticity over
the full chord of a foil.
[0019] The development of persistently streaming vorticity on both
a pressure and a suction face of a foil from a very low profile
vortex generator is contrary to published opinion by NASA, where
testing has shown that current art "micro" VG's on a flat surface
tend to develop vorticity downstream for no more than 40 times
their height. A difference in the conditions tested by NASA and the
observation of test of the invention is the surfaces that the
invention is applied to, when said surface is a foil, are not flat,
and they also operate at an angle of attack that allows the vortex
to retain sufficient energy to remain attached to the trailing edge
of the foil or blade.
[0020] The V form may be alternatively shaped as an ogival plan,
which is more effective at generating a streaming vortice than a V
however has limited surface area for adhesion.
[0021] The polyurethane tape provides a moderately robust erosion
protection surface, which can be readily replaced in the field,
following damage or excessive wear. The material is effective in
rain and sand erosion conditions as an erosion protection
surface.
[0022] An alternate application may use the reverse form as a mask
to terminate the sprayed or rolled on erosion protection polymer in
an advantageous arrangement. The film has a planform arrangement
that promotes advantageous development of vortices in either
streamwise or transverse directions, dependent on the application
sought. Variations of this film may optionally be applied
beneficially to the leading edge or trailing edge of a foil or
blade. In the case of the trailing edge, the mask film results in a
transverse polymer being formed on the trailing edge lower surface
which acts as a gurney tab.
[0023] Comparative to existing sprayed on or rolled on leading edge
erosion treatments, the invention removes the adverse effects of an
aft facing step at the trailing edge of the current art protective
tape layer which acts to trip the boundary layer and cause
premature transition to turbulent flow conditions in the boundary
layer, or in extreme cases premature separation of the boundary
layer. This condition increases drag of the surface, and acts
generally to reduce circulation and therefore lift coefficients.
The invention acts instead to additionally promote streamwise
vorticity, which reenergises the boundary layer, promoting improved
lift and potentially drag performance over a base section without
any treatments. Existing erosion protection surface including tapes
and paint adversely affect blade performance by approximately 2% to
4%. The application of the vortex generating system by use of the
advantageous incorporation in an erosion protection surface, tape
or other medium results in improved drag and lift performance of
the blade in comparison to untreated blades of between 7% to 10%.
The difference in performance between current art protection
systems and the invention is approximately a 12% to 15% improvement
in drag performance, and an additional improvement in lift
coefficient, and angle of attack capability for the treated
surface. For indicative initial values, a 120 mm tape applied to a
25' rotor leading edge, with a 183 mm chord 63015 profile,
operating at an RPM of 530 RPM, with vortex generator planforms of
18 mm length .times.12 mm base, applied at the outer 1.0 m of the
blade span, and with a 38 mm wide tape with ogival planform vortex
generators of a size of 12 mm length by 8 mm width applied to the
outer 250 mm of the leading edge of the tail rotor, which is 1.2 m
span, operating at approximately 3500 RPM, reduces drag by
approximately 10%. Additional indicative performance shifts include
a reduction in autorotation sink rate, of approximately 10%
consistent with the alteration of the figure of merit by a similar
amount, reduction in torque required to maintain the constant
operating rotor RPM of 10%, and a reduction in fuel flow of a
similar amount. Additionally, it is notable that rotor deceleration
on power loss to the rotor drive is at a lesser rate of RPM decay
than the baseline blade, which is consistent with an improved
figure of merit, resulting in an increase of Tau, the
characterisitc time. For a helicopter rotor blade so modified, the
increase in Tau increases the time available for the crew to
respond to a power failure and to enter autorotation. Further, on
commencing an autorotative flare, the rotor RPM recovery is
enhanced over current art, in that the RPM rise per g as a result
of the flare is greater due to the reduced drag, and improved
figure of merit. This factor results in an improved flare condition
where RPM rise is higher, and the system has additional performance
available to effect a successful landing. It should be noted that
current art erosion protection tapes and paint surfaces which
result in an aft facing step, adversely affect autorotation for the
same reasons, that the current art adversely affects figure of
merit through the reduction in lift and increase in drag over
baseline configuration.
[0024] It is obvious to a person skilled in the art that
application of a mass at the outer leading edge of a blade or rotor
affects inertial loadings. The most significant loadings so
affected are radial shear moment, pitch inertial moment, and in the
case of a rotor or blade, feathering inertial moment. For a case
where the invention directly replaces a current art erosion
protection surface, there is minimal variation in these values. For
a case where the invention is applied to a system that has not had
current art erosion protection mechanisms applied, then an analysis
of the impact of the additional mass to these areas is necessary,
to ensure that the specific case retains adequate structural
loading margins. Feedback through the flight control system in a
helicopter is important, and may be affected by such mass
additions, and needs to be assessed as a natural part of
certification for aircraft or helicopter application of the
invention. It is notable however, that in the case of the
helicopter, the reduction in drag results in a lowering of in plane
drag asymmetries, and thus acts to lower vibrational loads in
flight. Additionally, where applied further inboard in the rotor
span, the vortex generators delay stall condition occurring and
therefore reduce slightly the periodic perturbation to the blade
span from variations in spanwise lift development. In the case of a
helicopter, it is noted that the reduction in torque requirement
has impacts positively on torque loads throughout the transmission
system, lowering applied torque to all components. Additionally,
the lower torque requirement reduces the antitorque force required
to be applied to maintain directional control, and therefore
results in increased operational safety margins, lessening the risk
of loss of tail rotor effectiveness, in single rotor helicopter
configurations.
[0025] Manufacture of the film incorporating vortex generators is
able to be accomplished using CAD/CAM plotter cutter systems, or
alternatively by use of rotary cutters with the vortex generator
shape embodied as a continuous series. As the sizing of the vortex
generators, and width of the tape form by which the location of the
vortex generators is effected are determined by the blade profile,
Reynolds number and operating angels of attack, it is more
effective to conduct CAAD/CAM production for small run production
of tapes. The repeatability and registration accuracy of commercial
plotter cutters is adequate to achieve low mass variations between
tapes. Film with suitable properties for subsonic application in
areas without intense thermal heating are available as current art
paint protection films from 3M, such as the 8760 & 8999KIT
series, and from Avery Dennison, "Series 2010 Stoneguard".
Additional and comprehensive data on application of such tapes is
available from the US Army Erosion Protection Manual, and from the
respective manufacturers. MSDS data is available from the
manufacturer providing information on the suitability of the
material to the application desired.
[0026] Alternative application of a painted or rolled erosion
surface to a blade may be preferred in some embodiments, using the
mask to form the vortex generating shapes, however the application
of the erosion protection material will have larger variations in
the applied profile and therefore mass distribution. The final
product needs to be statically and preferentially dynamically
balanced to compensate for these mass variations.
[0027] Where a lap joint may be used in a product fabrication, the
application of a vortex generating trailing edge abutting to the
trailing edge of said lap joint would act to promote boundary layer
re-energising. This can be readily machined by CAD/CAM routing of
materials such as aluminium and glass or carbon reinforced
plastics. Additionally, plan shape can be incorporated by water jet
cutting or laser cutting dependent on the material.
[0028] An alternative mechanism for applying a conformal sub
boundary vortex generator to a lap joint may be achieved by
attachment of a plurality of chevrons which are abutted to the aft
face of the lap joint, with the apex of the chevron facing
downstream. The thickness of this chevron is preferably equal to
the lap joint thickness. While not the most desirable methodology
for reducing drag at a lap joint, this does allow a retrofit of a
mechanism to an existing structure, such as a current art airframe,
wing, or hull.
[0029] It should be noted that in any application of conformal sub
boundary vortex generators, the step pairing of said vortex
generators can be accomplished, however this is not suitable on any
component that is rotating, such as a blade or rotor, as the
intermix of the vortices from the upper or leading vortex generator
and the following step that develops the following vortices causes
a separation of the upper vortices form the surface, and these are
centrifuged radially as a consequence. Testing shows that the
centrifuging of these vortices then affect in turn the outboard and
lower series of vortices, with a resultant spanwise flow developing
that is adverse to performance. In non rotating applications, this
effect is not observed, and series may be employed effectively.
[0030] A plurality of conformal sub boundary vortex generators may
also be attached at the trailing edge of a section, with the apex
forward, and the base parallel with the trailing edge of the
section, but preferably located in the region of 0 to 2 times the
height of the vortex generator. The height of the vortex generator
should always be a low order of the local boundary layer thickness,
however vorticity is evident at very low heights, on the order of
the generators applied to the leading edge. At the trailing edge,
the reversed generator so described acts to develop 2 counter
rotating vortices that develop along the sides of the generator
form the apex, but tend to lift above the surface of the generator
towards the trailing edge. Additionally, at the trailing chordwise
or transverse edge of the generator, a further vortice is generated
bound by this edge and the surface of the section the generator is
attached to. This vortice acts in the same manner as a very low
height lift enhancing tab, or gurney tab. The streamwise vortices
so developed interact with the Von Karman Street vortex sheet
developed at the trailing edge of the section, and acts to disrupt
this into streaming filaments instead of a sheet. This action
reduces the momentum loss in the wake, and acts to delay tip
vortice rollup of the Von Karman Street, thus acting to lessen lift
induced drag. Application of any mechanism altering asymmetrically
the trailing edge of a section will develop a pitching moment
coefficient, which needs to be considered in the application. The
pitching moment if resulting in excessive moment may cause an
undesirable control demand or trim drag outcome, which can be
mitigated by the application of such vortex generating elements on
the opposite surface as well. Where applied on both sides, the
designer has an alternative to locate such additional generators
either in alignment or out of phase with the generators located on
the other side of the section. In general but not all cases, it is
desirable to attach such generators out of phase to promote the
interaction of the vortices from both sides of the section acting
on the Von Karman Street. In the case of a rotating blade or rotor,
the alteration of the vortex rollup will have an effect on the
intensity of the tip vortice and it's location. This change will
generally impact the intensity of the blade-vortice interaction,
but the extent will be dependent on the configuration and size of
the generators. While evidence on tab application from
computational fluid dynamics indicates that it is desirable to
apply a series of tabs (as the invention acts when attached
proximate to the trailing edge), along the complete span of a
rotor, full scale testing shows that this may be the result of
computer model limitations, and that in the case of a helicopter
rotor, the application is best embodied in the mid span region. The
aerodynamic pitching moment in such an embodiment of the invention
is moderate as long as the generators are kept to a low height,
which is also desirable from a lift/drag variation design
consideration. Inertial pitching moment needs to be considered,
which may increase control loads and vibration for conditions where
cyclic pitch is applied, however testing shows the effects are not
significant for low height generators. In testing, this moment was
offset by application of conformal sub boundary layer vortex
generators at the leading edge of the foil, balancing the inertial
moments around the blade feathering axis. Testing further showed
substantial vibration reduction, and substantial torque reduction,
indicative of the lift enhancing tab effect being developed.
Acoustic signature is changed by application of a tab system
(vented by spacing gaps or otherwise). A designer versed in the art
would naturally be aware that the addition of mass on a section can
be adverse to flutter boundary margins. Analysis and testing
indicate that the aerodynamic pitching moment is more significant
than the center of mass shift, and that with care taken to minimise
mass addition, the net outcome is an improved flutter margin. In
the case of a helicopter rotor, the onset of flutter is
additionally mitigated by the cyclical pitch rates. Application of
a mechanism acting as a mid span trailing edge tab, additionally
develops greater lift in the mid span region of a foil and unloads
the tip, thereby allowing a lower collective blade angle to be
applied for a given total lift developed, minimising the impact of
critical mach number on the tip of the foil, and resultant
drag.
[0031] It is evident from the preceding that the invention is a
passive mechanism, that mitigates the effects of current art
structural design and erosion protection methods, and results in
performance enhancement. A review of the bibliographic references
will identify the basic mechanisms of flow that exist, and provides
sufficient data for a parametric optimisation by a person skilled
in the art.
[0032] It is advantageous to form a serrated or multiple V shaped
trailing edge to an erosion layer on a foil or blade.
[0033] For a sprayed on or rolled on polymeric erosion surface
applied to a surface, a mask with an embedded shape will result in
advantageous profile being laid.
[0034] It would be advantageous to provide an elastomeric film that
can conform to the surface profile of the foil or blade.
[0035] It would also be advantageous to provide a planform shape to
the film which provides for chordwise or near chordwise promotion
of vortices in the boundary layer of the foil or blade. These are
applied to the upper surface, and in general to the lower
surface.
[0036] It would further be advantageous to provide a high shear
adhesive that allows for some movement of the substrate and surface
treatment.
[0037] At a lap joint, it would be advantageous to apply a
plurality of conformal sub boundary layer vortex generators with
the apex aligned towards the rear, to re energise the boundary
layer.
[0038] At a trailing edge of a foil or surface, it is advantageous
to apply a series of conformal sub boundary layer vortex
generators, with the apex facing forward toward the flow, to
develop a set of counter rotating vortices to interact with and
disrupt the Von Karman Street sheet into filaments, thereby
delaying the onset of tip vortex rollup. Said trailing edge
mechanisms additionally advantageously develop a transverse vortex
in the wake of the base of the generator, which acts as a lift
enhancing tab, advantageously improving lift and drag ratios in
specific operational cases. Such an application advantages the lift
distribution on a span, by unloading the tip of the span.
[0039] It is further advantageous to provide vortex generation with
a mechanism that adds low mass to a system.
[0040] Damage tolerance by material and by design is advantageous
for a vortex generating and flow modification system.
BRIEF DESCRIPTION OF THE DRAWINGS
[0041] A complete understanding of the present invention may be
obtained by reference to the accompanying drawings, when considered
in conjunction with the subsequent, detailed description, in
which:
[0042] FIG. 1 is a top perspective view of a generic foil;
[0043] FIG. 2 is a top perspective view of a foil with a current
art erosion protection layer or tape applied;
[0044] FIG. 3 is a top plan view of an elastomeric erosion
protection tape or application medium tape element incorporating
sub boundary vortex generators;
[0045] FIG. 4 is a top perspective view of a current art erosion
protection tape with v form sub boundary vortex generators applied
at the aft facing step;
[0046] FIG. 5 is a top perspective view of a foil with a vortex
generating application medium or vortex generating erosion
protection layer applied;
[0047] FIG. 6 is a section view of an of a foil showing general
flow conditions;
[0048] FIG. 7 is a plan view of an elastomeric erosion protection
tape or application medium tape element incorporating ogival form
sub boundary vortex generators;
[0049] FIG. 8 is a plan view of an elastomeric erosion protection
tape or application medium tape element incorporating v form sub
boundary vortex generators;
[0050] FIG. 9 is a plan view of a mask tape element incorporating v
form sub boundary vortex generator shapes and a tip half v vortex
generator form to facilitate application of an erosion protection
paint or medium of beneficial planform shape;
[0051] FIG. 10 is a top perspective view of a series of vortex
generators applied by an erosion protection layer or application
medium incorporating sub boundary layer vortex generators;
[0052] FIG. 11 is a bottom perspective view of a series of
asymmetrically applied trailing edge chevrons; and
[0053] FIG. 12 is a bottom perspective view of a series of out of
phase upper and lower trailing edge chevrons.
[0054] For purposes of clarity and brevity, like elements and
components will bear the same designations and numbering throughout
the Figures.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0055] FIG. 1 is a top perspective view of a generic foil. This
drawing shows the foil leading edge 26, foil or aero/hydrodynamic
surface 10, and foil trailing edge 28.
[0056] FIG. 2 is a top perspective view of a foil with a current
art erosion protection layer 12 or tape applied, to a foil or
aero/hydrodynamic surface 10. It can be seen that the process of
placing a tape around a foil leading edge 26 results in two aft
facing edge 30 elements being produced, on the upper and lower
faces of the foil or aero/hydrodynamic surface 10.
[0057] FIG. 3 is a top plan view of an elastomeric erosion
protection layer 12 tape or application medium 14 tape element
incorporating sub boundary vortex generators.
[0058] FIG. 4 is a top perspective view of a current art erosion
protection tape with v form sub boundary layer vortex generators 16
applied at the aft facing edge 30. sub boundary layer vortex
generators 24 are applied abutted in this case to the aft facing
step or lapjoint 48 of the structure, depicted as v form sub
boundary layer vortex generators 16. Such an application may be
conducted on a current structure to minimise the area of aft facing
edge 30 that exists at the location of lapjoints, generally in
elastomeric application medium 14 of the same thickness as the lap
joint. In this application, either v form chevrons or ogival form
chevrons may be applied adhesively to the substrate. In such an
application laminate substrate vents 46 may be incorporated to
increase adhesion and minimise distortion of the application layer
to the substrate.
[0059] FIG. 5 is a top perspective view of a foil with a vortex
generating application medium 14 or vortex generating erosion
protection layer 12 applied. the sub boundary layer vortex
generators 24 thus applied develop a plurality of counter rotating
vortices, one form each face, which convect along the freestream
flow. These vortices act to re-energise the lower boundary layer by
entraining fluid from the free stream and directing this flow
towards the lower boundary layer. The re-energising of a boundary
layer has a known capacity to promote reduced drag in the boundary
layer, by reducing the momentum layer thickness. The improved
dynamics lead to a delay of development of the thickening of the
boundary layer at the transition point into a turbulent boundary
layer, and also delay the adverse pressure gradient in the boundary
layer that ultimately results in separation of the boundary layer
flow from the surface. The outcome of these improvements is
improved drag characteristics, improved coefficient of lift for a
given angle of attack, and increased angle of attack capability
before aerodynamic stall occurs.
[0060] FIG. 6 is a of a foil showing general flow conditions as
discussed above. The application of sub boundary layer vortex
generators 24 is generally in the region forward of the transition
point, in the laminar boundary layer region 38. The voticity
generated extends up the trailing edge of the foil. The position of
the upper boundary layer transition point 32, lower boundary layer
transition point 34 and separation point 36 can be evaluated using
current art analysis based on Reynolds number, the arbitrary foil
or aero/hydrodynamic surface 10 shape and knowing the angle of
attack of the shape.
[0061] FIG. 7 is a plan view of an elastomeric erosion protection
layer 12 tape or application medium 14 tape element incorporating
ogival planform sub boundary vortex generator 18 planforms.
[0062] FIG. 8 is a plan view of a elastomeric erosion protection
layer 12 tape or application medium 14 tape element incorporating v
form sub boundary layer vortex generators 16.
[0063] FIG. 9 is a plan view of a sub boundary layer vortex
generator mask 44 tape element incorporating v form sub boundary
layer vortex generators 16 shape and a tip half v vortex generator
form to facilitate application of an erosion protection paint or
medium of beneficial planform shape. The vortex generating
structure is applied as a sprayed or rolled application medium 14,
which is preferred by the designer. Such medium may be a paint, or
other erosion protection material as chosen by the designer as
incorporating desirable properties.
[0064] FIG. 10 is a top perspective of a series of vortex
generators applied by an erosion protection layer 12 or application
medium 14 incorporating sub boundary layer vortex generators 24, to
a foil or aero/hydrodynamic surface 10.
[0065] FIG. 11 is a bottom perspective view of a series of
asymmetrically applied trailing edge chevrons. The sub boundary
layer trailing edge chevron 50 series is located with the base from
2 times the height of the chevron to zero times the height forward
of the trailing edge. The distance between the chevrons may be in
the order of 1 to 10 times the width of the base, dependent on
application velocities, and the apex angle. It can be assumed that
an ogival planform may be applied as an alternate planform.
[0066] FIG. 12 is a bottom perspective view of the series of out of
phase upper and lower trailing edge chevrons. The dotted centre
chevron is located on the upper surface, whereas the other two
solid line delineated chevrons are on the lower surface of the
foil. The sub boundary layer trailing edge chevron 50 may be a
triangular planform or alternatively an ogival form. The base is
parallel to the trailing edge, and where incorporated on a swept
trailing edge, it will result in a planform that is not symmetrical
across the height of the chevron from the base.
[0067] Since other modifications and changes varied to fit
particular operating requirements and environments will be apparent
to those skilled in the art, the invention is not considered
limited to the example chosen for purposes of disclosure, and
covers all changes and modifications which do not constitute
departures from the true spirit and scope of this invention.
[0068] Having thus described the invention, what is desired to be
protected by Letters Patent is presented in the subsequently
appended claims.
* * * * *