Fibrillar structures to reduce viscous drag on aerodynamic and hydrodynamic wall surfaces

Patent metadata

Field	Value
Publication number	US-2016017902-A1
Application number	US-201414774767-A
Country	US
Kind code	A1
Filing date	Mar 12, 2014
Priority date	Mar 12, 2013
Publication date	Jan 21, 2016
Grant date	—

Abstract

An aerodynamic or hydrodynamic wall surface has an array of fibrillar structures disposed on and extending from the wall surface, wherein each fibrillar structure comprises a stalk and a tip. The stalk has a first end and a second end, wherein the first end is attached to the wall surface, and the stalk is oriented with respect to the wall surface at a stalk angle between approximately 1 degrees and 179 degrees. The tip has a first side and a second side, wherein the first side is attached proximate to the second end of the stalk, the tip has a larger cross-sectional area than the stalk, and the second side comprises a substantially planar surface that is oriented with respect to the stalk at a tip angle between approximately 0 degrees and 90 degrees.

First claim

1 . An aerodynamic or hydrodynamic wall surface comprising:
an array of fibrillar structures disposed on and extending from the wall surface, wherein each fibrillar structure comprises a stalk and a tip; the stalk having a first end and a second end, wherein the first end is attached to the wall surface, and the stalk is oriented with respect to the wall surface at a stalk angle between approximately 1 degree and 179 degrees; and the tip having a first side and a second side, wherein the first side is attached proximate to the second end of the stalk, the tip has a larger cross-sectional area than the stalk, and the second side comprises a substantially planar surface that is oriented with respect to the stalk at a tip angle between approximately 0 degrees and 90 degrees.

2 . The wall surface as recited in claim 1 , wherein the stalk angle is between approximately 45 degrees and 90 degrees.

3 . The wall surface as recited in claim 1 , wherein a cross section of the stalk is substantially square shaped, rectangular shaped, circular shaped, elliptically shaped, triangular shaped, hexagonally shaped or multi-sided prism shaped.

4 . The wall surface as recited in claim 1 , wherein the second side of the tip is substantially square shaped, rectangular shaped, circular shaped, elliptically shaped, triangular shaped, hexagonally shaped or multi-sided prism shaped.

5 . The wall surface as recited in claim 1 , wherein the stalk and tip form a mushroom shape.

6 . The wall surface as recited in claim 1 , wherein the stalk and tip are formed from a single material.

7 . The wall surface as recited in claim 1 , wherein the wall surface, each stalk and each tip are formed from a single material.

8 . The wall surface as recited in claim 1 , wherein each stalk and tip are made of a silicone rubber, a polyurethane plastic, a thermoplastic, a thermoset, a UV curable material, a polymer or a combination thereof.

9 . The wall surface as recited in claim 1 , wherein the each stalk and tip are formed by micro/nano-molding one or more templates.

10 . The wall surface as recited in claim 9 , wherein the one or more templates are produced using a photolithography process and/or etching process.

11 . The wall surface as recited in claim 1 , wherein:
each stalk has a stalk diameter of approximately 10 nm to 1000 μm, and a length of approximately 10 nm to 1000 μm; each tip has a tip diameter of approximately 10 nm to 2000 μm; and a center of each stalk is separated from a center of an adjacent stalk by approximately 10 nm to 5000 μm.

12 . The wall surface as recited in claim 1 , wherein:
each stalk has a stalk diameter of approximately 50 μm and a length of approximately 100 μm; each tip has a tip diameter of approximately 100 μm; and a center of each stalk is separated from a center of an adjacent stalk by approximately 120 μm.

13 . The wall surface as recited in claim 1 , wherein the stalks in the array of fibrillar structures are arranged in a square packing, a hexagonal packing or a random packing.

14 . The wall surface as recited in claim 1 , wherein the fibrillar structures within the array have varying cross-sectional shapes, diameters and/or spacings.

15 . The wall surface as recited in claim 1 , wherein a lift of the wall surface is increased as compared the wall surface without the array of fibrillar structures.

16 . The wall surface as recited in claim 1 , wherein a drag of the wall surface is reduced by at least 30% as compared the wall surface without the array of fibrillar structures.

17 . The wall surface as recited in claim 1 , wherein a lift-to-drag ratio of the wall surface is increased as compared the wall surface without the array of fibrillar structures.

18 . The wall surface as recited in claim 1 , wherein at least a portion of the wall surface comprise a curved surface.

19 . The wall surface as recited in claim 1 , wherein the wall surface comprises at least a portion of wind turbine blade, a propeller, a wing, an airfoil, a flight control surface, a hull of a ship or a submarine, a land-based vehicle, an manned or unmanned aerial vehicle, a pipeline or a stationary structure.

20 . The wall surface as recited in claim 1 , further comprising one or more additional arrays of fibrillar structures having one or more of a different stalk angle, a different stalk shape, a different stalk length, a different stalk diameter, a different tip angle, a different tip shape, a different tip length, a different tip diameter, a different spacing, a different packing or a different backing layer thickness.

Assignees

• Univ Texas Tech System
• Nanogriptech Inc

Inventors

• Castillo Luciano
• Aksak Burak
• Sitti Metin

Classifications

• F15D1/003 Primary

  comprising surface features, e.g. indentations or protrusions (F15D1/0055, F15D1/006 take precedence) · CPC title

• B64C2230/26

  by using rib lets or hydrophobic surfaces · CPC title

• B64C21/10

  using other surface properties, e.g. roughness · CPC title

• B63B1/36

  using mechanical means · CPC title

• F15D1/0035

  in the form of riblets · CPC title