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Lift Values Way Off For Wing in Solidworks

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Old   September 25, 2014, 22:03
Default Lift Values Way Off For Wing in Solidworks
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Hello Everyone,

I'm a college student on a design team and we are designing a plane that needs to carry 20 lbs of payload. We made our own optimized airfoil and I I've modeled up what our wing will look like. Our calculations (which include finite wing effects and take into account the taper, etc) show that we should get a lift around 27-30 lbs at zero AoA. We ran tests in xflr5 to verify this.

My problem is that I can't get even a remotely accurate lift reading. I'm constantly getting between 5 and 7 lbs. I've look everywhere I can think to find what I'm doing wrong but it seems like I'm doing everything right.

I started with the default domain, but found that was wayy to small, so I bumped it up to excessive sizes, and still get a low reading (see link "comp domain).

As for the general settings, I have it set to external, exclude cavities without flow conditions and exclude internal space. I'm running off the stock air fluid at sea level values. The walls are adiabatic and have zero roughness. The velocity is 35 mile/hour straight on.

I'm running the sim on mesh detail 4... I've run it on max (8) and got the same lift value.

I'm calculating my lift by simply setting up a global variable in the vertical direction.

The flow visualization looks correct when I animate it and such, but the values are just awful.

I would really appreciate any help on this. I've looked at every other thread I could find and tried all their suggestions to no luck. If you would like the model to run tests on, perhaps in a different software than what I have access to, I would love that. That would let me know if it's something wrong with my software or with the design in general. I don't see a way to upload a cad file though, so I'd need some help getting the file to you.

Thanks in advance,
Attached Images
File Type: jpg comp domain.jpg (21.8 KB, 9 views)
File Type: jpg overall iso.jpg (19.9 KB, 10 views)
File Type: jpg Airfoil Shape.jpg (16.0 KB, 6 views)
File Type: jpg front.jpg (6.6 KB, 6 views)
File Type: jpg top.jpg (17.0 KB, 7 views)
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