I used Profili to generate the points for an airfoil recently, and it had
a zero thick te. I tgransfered the points to my
CAD system and drew a spline from te across the upper surface, around the
le to the te. Then separated the spline at the upper surface max thick
point. I then made a point ofset above the te the required amount and
calculated the angle between the max thick pt on upper surface and the two
te points. I then rotated the rear upper surface about the max thick
point through the angle just found and it looks real good. After cutting
out templates and smoothing with sandpaper, airfoil is real fair. This
takes longer to say then to do, try it.
.........bc ([EMAIL PROTECTED])
also: ([EMAIL PROTECTED])
http://www.widomaker.com/~conk
Williamsburg, VA 23185
On Mon, 16 Jul 2001, Oleg Golovidov wrote:
> Forwarding Mark Drela's reply to everybody. Mark forgot to CC the list when
> replying.
>
> Thanks a lot, Mark.
> One more comment/question. If the chop-off method is acceptable, it is much
> easier to implement. Just plot the same airfoil for a larger chord.
> The method with opening the arches requires doing some preprocessing of the
> airfoil coordinates, right? Do you just use a spreadsheet to multiply the
> y-coord by the fraction of the x-coord (distance from LE)? Actually, one would
> need to add/subtract the correction factor of say 0.005*x, correct?
> Did you try to imply that if one chops off a good bit of the airfoil's tail it's
> no longer close to the original flow?
> Oleg.
>
>
> ------------- Begin Forwarded Message -------------
> From: Mark Drela <[EMAIL PROTECTED]>
>
>
> Oleg,
>
> The "chop-off" method is usually OK, but on airfoils with
> very thin rear ends like most of the new HLG stuff you'd
> have to chop off quite a bit to get 1% thickness. I like
> the other way better.
>
> >if you MUST have a thick trailing edge, do NOT round
> >it, leave it square.
>
> Yes, absolutely. On a lifting airfoil, the bottom-surface
> corner in particular should be sharp, otherwise the BL
> might stick partway around the curve and turn the flow
> upward and reduce lift. Of course if you -want- a
> lower CL this might help, but reducing camber is
> a far better way to do this.
>
> The rounding is deleterious only when the radius is
> a significant fraction of the bottom BL thickness,
> so this is less of a problem at smallish Re's.
> Still, I don't see a good reason to round off the edge
> in any case.
>
> - Mark
>
> ------------- End Forwarded Message -------------
>
>
> ______________________________________________________________________
>
> Oleg Golovidov
> Engineous Software Inc.
> www.engineous.com
> (919)677-6700 x107
>
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