Radar energy absorbing deformable low drag vortex generator

Patent metadata

Field	Value
Publication number	US-9677580-B2
Application number	US-201615227921-A
Country	US
Kind code	B2
Filing date	Aug 3, 2016
Priority date	Dec 31, 2012
Publication date	Jun 13, 2017
Grant date	Jun 13, 2017

Abstract

A family of Radar energy Absorbing Deformable Low Drag Vortex Generators (RAD-LDVG) is described herein. This family of devices are fabricated in such a way that it can conform to aircraft surface features while reducing radar returns from structural details. Vortex generators (VGs) are typically used to reattach or smooth gross flowfields over aircraft surfaces. By doing so, an airfoil or wing can maintain attached flow at higher angles of attack and/or higher lift coefficients than one without the VGs. These devices are also used to reattach and/or smooth flows that encounter crossflow-induced instabilities and/or adverse pressure gradients on the upper surfaces of wings or near aircraft boattails. Other uses include reduction of buffet, vibration, flutter, cavity resonance or general bluff-body pressure drag reduction. Although conventional rigid VGs do generate vortical aerodynamic structures, two major problems are often experienced: i.) the inability to conform to curved surfaces, ii.) the generation of radar cross-section spikes produced by the VGs themselves.

First claim

What is claimed is:

1. A device which is shaped so as to produce stream-wise vortices when attached to a non-uniform surface exposed to airflow, comprising:
a vortex generator having an upstream end and a distal downstream end, where the vortex generator has a lateral width and a vertical height and a flexible bottom surface configured to mount on the non-uniform surface exposed to airflow where the vertical height of the vortex generator is tapered to increase from the upstream end to the distal downstream end forming a concave upper surface, the concave upper surface having an apex peak at the distal downstream end, and where the lateral width of the vortex generator is tapered to decrease from the upstream end to the distal downstream end forming concave sidewalls; and
said vortex generator constructed of a material sufficiently flexible to deform responsive to increased pressure from a flow field to thereby reduce said vortex generators vertical height at the apex peak from an initial height to a reduced height.

2. The device as recited in claim 1 , conformed to one of a raised surface raised above and a recessed surface recessed below the non-uniform surface.

3. The device as recited in claim 1 , wherein said material sufficiently flexible to deform responsive to increased pressure possess a yield strain of greater than 0.5%.

4. The device as recited in claim 1 , wherein said material sufficiently flexible to deform responsive to increased pressure has an averaged electrical resistivity of greater than approximately 1×10 −8 Ω-m, but less than approximately 1×10 −10 Ω-m.

5. The device of claim 1 , wherein said material sufficiently flexible to deform responsive to increased pressure is bulk radar-absorbent material.

6. The device of claim 1 , wherein said material sufficiently flexible to deform responsive to increased pressure is layers of one of radar absorbent and radar-reflective material which form internal Jaumann absorbers.

7. The device of claim 1 , having an internal structure comprising radar absorbing and radar reflecting microstructures forming radio frequency wedge traps.

8. The device of claim 1 , wherein the bottom surface is one of concave, flat and hollow, thereby allowing for attachment to the non-uniform surface and accommodating of structural details which lie on the non-uniform surface.

9. The device of claim 1 , wherein said material sufficiently flexible to deform responsive to increased pressure is a RADAR absorbing material and internally structurally arranged such that an outermost surface is semi dielectric and an internal portion is constructed of semi conductive material.

10. The device of claim 1 , wherein said device comprises a plurality of vortex generators and said device includes overlapping the distal downstream end of said vortex generator over the upstream end of a second of said plurality of vortex generators.

11. A device which is shaped so as to produce stream-wise vortices when attached to a non-uniform surface exposed to airflow, comprising:
a vortex generator having an upstream end and a distal downstream end, where the vortex generator has a lateral width and a vertical height and a flexible bottom surface configured to mount the non-uniform surface exposed to airflow where the vertical height of the vortex generator is tapered to increase from the upstream end to the distal downstream end forming a concave upper surface, the concave upper surface having an apex peak at the distal downstream end, and where the lateral width of the vortex generator is tapered to decrease from the upstream end to the distal downstream end forming concave sidewalls; and
said vortex generator is constructed of a RADAR absorbing material and internally structurally arranged such that an outermost surface is semi dielectric and an internal portion is constructed of semi conducive material.

12. The device of claim 11 where the flexibility of the material is such that the vertical height reduces as a dynamic pressure of the flow field increases.

13. The device as recited in claim 11 , wherein said material sufficiently flexible to deform responsive to increased pressure possess a yield strain of greater than 0.5%.

14. The device as recited in claim 11 , wherein said material sufficiently flexible to deform responsive to increased pressure has an averaged electrical resistivity of greater than approximately 1×10 −8 Ω-m, but less than approximately 1×10 −10 Ω-m.

15. The device of claim 11 , wherein said material sufficiently flexible to deform responsive to increased pressure is bulk radar-absorbent material.

16. The device of claim 11 , wherein said material sufficiently flexible to deform responsive to increased pressure is layers of one of radar absorbent and radar-reflective material which form internal Jaumann absorbers.

17. The device of claim 11 , having an internal structure comprising radar absorbing and radar reflecting microstructures forming radio frequency wedge traps.

18. The device of claim 11 , wherein the bottom surface is one of concave, flat and hollow, thereby allowing for attachment to the non-uniform surface and accommodating of structural details which lie on the non-uniform surface.

19. The device of claim 11 , wherein said device comprises a plurality of vortex generators and said device includes overlapping the distal downstream end of said vortex generator over the upstream end of a second of said plurality of vortex generators.

Assignees

• Univ Kansas

Inventors

• Barrett Ronald M

Classifications

• F15D1/004 Primary

  oriented essentially parallel to the direction of flow · CPC title

• B64C21/02

  by use of slot, ducts, porous areas or the like · CPC title

• H01Q17/004

  using non-directional dissipative particles, e.g. ferrite powders (H01Q17/005 takes precedence; flake-like H01Q17/002) · CPC title

• G03G13/283

  obtained by a process including the transfer of a tonered image, i.e. indirect process · CPC title

• G03G13/26

  for the production of printing plates for non-xerographic printing processes · CPC title