Why I'm I getting cd 50 on one side of the wing but not on the other side?

[Ismeret Tenger]

Hi,

I have a small AR wing and at one edge it shows much different value by VSPAERO than on the other side.  See attached image.

Any good hint?

Thanks ahead,

János

[Rob McDonald]

If you're doing load distributions of thick-surface panel codes, you may want to use the experimental file format option on the Advanced tab.  It does a better job with load distributions.

The spanwise resolution on this model is not really appropriate -- at a minimum, you need more resolution on the tiny wing tabs, you also likely need more on the transition from the center body to the tabs.

Rob

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[Ismeret Tenger]

Hi Rob,

There is no panel code here, it is all VLM.  Well, I am looking airfoils with T/C minimum 25%.  Yes, you are right, I should do something around this tiny wing outtruders, because they really can ruin the run if their profile has some concavity.  Maybe in my next step.  If the T/C is so high I probably should look the experimental file format to get the goodies from both approaches as you are recommending.  That will be my next for the best 5 from the  18 I found.  Many among these are not watertight airfoils, so I made sure the first and the last data lines for z end in 0.0000000.

Interestingly, almost all of the airfoils that has concave curves, the Cp has big jumps up and down as I increase the alpha from 0 to 25.  I have the feeling if the airfoil line would not be quadratic or higher order curve, just plane lines, then there would be one which would have better characteristics than the curved one, because the lifting part of the surface would be bigger for the given alpha.  I might do a little Mathematica program to run a genetic algorithm to find best line segment shapes for a given circumference if the major airfoil parameters like chord and camber  and number of points are the same.

Thanks a lot,

János