Durable riblets for engine environment

1. An airfoil defining a leading edge, a trailing edge, and an airfoil surface extending between the leading edge and the trailing edge, the airfoil comprising a first riblet array laminate on the airfoil surface, the first riblet laminate comprising:

a first adhesive layer on at least a first portion of the airfoil surface;

a first riblet array sheet disposed on at least a portion of the first adhesive layer, wherein the first riblet array sheet defines a first plurality of contiguous geometric features having peaks and valleys extending in a first rib direction, and wherein the first plurality of contiguous geometric features define a total width to total height ratio W:H of about 1:1 to about 2.5:1; and

further comprising a second riblet array laminate comprising:

a second adhesive layer on at least a second portion of the airfoil surface;

a second riblet array sheet disposed on at least a portion of the second adhesive layer, wherein the second riblet array sheet defines a second plurality of contiguous geometric features having peaks and valleys extending in a second rib direction, wherein the second plurality of contiguous geometric features define a total width to total height ratio W:H of about 1:1 to about 2.5:1, and

wherein the second rib direction is different than the first rib direction.

2. The airfoil as in claim 1 , wherein the airfoil is for a gas turbine engine.

3. The airfoil as in claim 1 , wherein the maximum total height of the first plurality of contiguous geometric features is about 0.66 mm or less.

4. The airfoil as in claim 1 , wherein the total width to total height ratio W:H of the first plurality of contiguous geometric features is about 1.25:1 to about 2.25:1.

5. The airfoil as in claim 1 , wherein the first plurality of contiguous geometric features have a yaw angle β 1 within about 45 degrees from a direction of a tangent line extending from the leading edge in the axial direction.

6. The airfoil as in claim 1 , wherein the first plurality of contiguous geometric features have a yaw angle β 1 within about 2 degrees to about 35 degrees from a direction of a tangent line extending from the leading edge in the axial direction.

7. The airfoil as in claim 1 , wherein the first riblet array laminate and second riblet array laminate extend from the trailing edge to the leading edge to cover about 75% to about 99% of the airfoil surface in the axial direction A therebetween.

8. The airfoil as in claim 1 , wherein the leading edge defines a substantially smooth surface, and wherein the second plurality of contiguous geometric features have a maximum total height of about 0.65 mm or less.

9. The airfoil as in claim 1 , wherein the first riblet array sheet and the second riblet array sheet comprise an elastomeric material.

10. A gas turbine engine, comprising:

a fan section comprising at least one fan blade, blisk, outlet guide vane, or any combination of one or more fan blade, blisk, and one or more outlet guide vane,

a compressor,

a combustor disposed downstream from the compressor, and

a turbine disposed downstream from the combustor,

wherein the engine comprises at least one airfoil defining a leading edge, a trailing edge, and an airfoil surface extending between the leading edge and the trailing edge, the airfoil comprising,

a first riblet array laminate comprising,

a first adhesive layer on at least a first portion of the airfoil surface,

a first riblet array sheet disposed on at least a portion of the first adhesive layer, wherein the first riblet array sheet defines a first plurality of contiguous geometric features having peaks and valleys extending in a first rib direction, and wherein the first plurality of contiguous geometric features define a total width to total height ratio W:H of about 1:1 to about 2.5:1,

a second riblet array laminate comprising,

a second adhesive layer on at least a second portion of the airfoil surface,

a second riblet array sheet disposed on at least a portion of the second adhesive layer, wherein the second riblet array sheet defines a second plurality of contiguous geometric features having peaks and valleys extending in a second rib direction, and wherein the second plurality of contiguous geometric features define a total width to total height ratio W:H of about 1:1 to about 2.5:1, and

wherein the second rib direction is different than the first rib direction.

11. The engine as recited in claim 10 , wherein the first riblet array laminate and second riblet array laminate exhibit a second erosion resistance that is greater than or equal to a first erosion resistance of the airfoil surface.

12. The engine as recited in claim 10 , wherein the first plurality of contiguous geometric features and second plurality of contiguous geometric features comprise curved valleys.

13. The engine as recited in claim 10 , wherein a peak angle α of the first plurality of contiguous geometric features and the second plurality of contiguous geometric features is about 75 degrees to about 105 degrees.

14. The engine as recited in claim 10 , wherein the first plurality of contiguous geometric features and second plurality of contiguous geometric features is shaped in a sawtooth pattern.

15. The engine as recited in claim 10 , wherein the first riblet array laminate and second riblet array laminate are disposed on at least one component in the fan section, and wherein the first plurality of contiguous geometric features define a total width to total height ratio W:H of about 1:1 to about 2.5:1 with a maximum total height of about 0.65 mm or less, and wherein the second plurality of contiguous geometric features define a total width to total height ratio W:H of about 1:1 to about 2.5:1 with a maximum total height of about 0.65 mm or less.

16. A method of providing erosion protection to an airfoil surface comprising the steps of:

adhering a first riblet array laminate to the airfoil, the first riblet array laminate comprising a first adhesive layer on at least a first portion of the airfoil surface, and a first riblet array sheet disposed on at least a portion of the first adhesive layer, wherein the first riblet array sheet defines a first plurality of contiguous geometric features having peaks and valleys extending in a first rib direction, and wherein the first plurality of contiguous geometric features define a total width to total height ratio W:H of about 1:1 to about 2.5:1, and

adhering a second riblet array laminate to the airfoil, the second riblet array laminate comprising a second adhesive layer on at least a second portion of the airfoil surface, and a second riblet array sheet disposed on at least a portion of the second adhesive layer, wherein the second riblet array sheet defines a second plurality of contiguous geometric features having peaks and valleys extending in a second rib direction that is different from the first rib direction, and wherein the second plurality of contiguous geometric features define a total width to total height ratio W:H of about 1:1 to about 2.5:1.

17. The method as recited in claim 16 , wherein the first riblet array laminate and second riblet array laminate exhibit a second erosion resistance that is greater than or equal to a first erosion resistance of the airfoil surface.

18. The method as in claim 16 , wherein the first riblet array sheet and second riblet array sheet comprise an elastomeric material.

19. The method as in claim 16 , wherein a peak angle α of the first plurality of contiguous geometric features and the second plurality of contiguous geometric features is about 75 degrees to about 105 degrees, and wherein the first plurality of contiguous geometric features define a total width to total height ratio W:H of about 1:1 to about 2.5:1 with a maximum total height of about 0.65 mm or less, and wherein the second plurality of contiguous geometric features define a total width to total height ratio W:H of about 1:1 to about 2.5:1 with a maximum total height of about 0.65 mm or less.