Rose thorn wingtip for the 55 humpback wind turbine, (as revision1) .

External surfaces .

3 February 2011 .

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This wingtip revises the 55 humpback wind turbine, (posted 21 January 2011) .

It draws its basic form from the serrated #aises designs, (most recently posted as the 56 aises brittle star, on 27 January 2011) .

I hope that it will moderate, (if not eliminate), the wingtip vortices which the 55 would otherwise form .

( The nature of these was also covered in the 56 brittle star's post. )

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The differential between the high pressure (ventral) side of a wing and the low pressure (dorsal) side

can drive a 'siphon effect' across the outside face of the wingtip .

There, air near the wing's ventral surface will be sucked 'out from under' the wing towards the dorsal surface .

This current mixes with the dorsal and passing air flows to form a vortex which trails behind the wing tip .

Such vortices can be the cause of mischief, and i believe, noise and wear .

They also drain off some of the useful wind energy which would otherwise drive the turbine .

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The windward curve of this rose thorn wingtip, (based on a hyperbolic sine),

seeks to interfere with vortex formation at the siphon's 'sweet spot' ;

(That point where the pressure differential is strongest ~ about 1/4 to 1/3 of the way back from the forward edge) .

Without enough material to block the siphon,

(which has the entire upper and lower surfaces of the wing to draw upon),

it offers a surface upon which the air current can wrap backward laminarly .

The leeward curve, (based on a hyperbolic cosine), seeks to place the siphon at a disadvantageous angle, (pulling air upwind), should it seek that edge .

It may also have the effect of spreading out what high pressure air might come its way, diffusing the flow .

Structurally, i believe these two related curves are a good match ; though the point may be attractive to lightning .

Making it non-conductive, replaceable, and with a non-wetting surface could help address this .

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Complementing the rose thorn curves, the wing's cross section is changed from a lifting geometry to a neutral one just prior to the base of the thorn .

This can be seen as a 'belly' on the ventral side of these figures .

The thorn maintains this lift-neutral geometry to its tip .

The objects are : to give the siphon effect less foothold at the wing tip, so that the wind would carry it toward the trailing edge of the thorn ;

to strengthen the thorn, as the wing's most delicate area ; and aesthetic .

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The very tip, in this case, is modeled without an implied bulb, (red in the post of the 21st) ; and has a flatter arch, lowering its wind resistance .

Its base is right at the 8pi/5 mark, so i expect it would encounter slight ripple effects from the tip of the wing behind it when the turbine is at sync speed .

This revision makes the wings slightly longer than the drafts of the 21st and previous .

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The figures provide views of the tip, along with a short stretch of wing leading up to it .