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Wing lift in Solidwork Flow Simulation

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Old   April 9, 2011, 10:45
Default Wing lift in Solidwork Flow Simulation
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Hi!
I'm pretty new to CFD, and trying to use Solidworks Flow Simulation to find the lift generated by a wing. I have calculated in theory that it should be around 50-60N and confirmed using NASA FoilSim, however the result I'm getting from Flow Simulation is only about 8.5N.

Has anyone encountered anything like this before and could give me some pointers as to where I might be going wrong? I have set the air velocity the same in the simulation as in the calculation and ensure it is calculating for external flow excluding internal space. I have attached a screenshot of my set up if it helps.

I am pulling my hair out here and could really use any help!
Thanks.
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Old   April 10, 2011, 01:45
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Quote:
Originally Posted by brianmcv View Post
Hi!
I'm pretty new to CFD, and trying to use Solidworks Flow Simulation to find the lift generated by a wing. I have calculated in theory that it should be around 50-60N and confirmed using NASA FoilSim, however the result I'm getting from Flow Simulation is only about 8.5N.

Has anyone encountered anything like this before and could give me some pointers as to where I might be going wrong? I have set the air velocity the same in the simulation as in the calculation and ensure it is calculating for external flow excluding internal space. I have attached a screenshot of my set up if it helps.

I am pulling my hair out here and could really use any help!
Thanks.
Hi,
Can you post more details of your simulation like the type of geometry, mach number, type of grid that you have made and numerical procedure that you are following. With these details someone should be able to point any possible errors in you modelling.
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Old   April 10, 2011, 05:02
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Hi,
The geometry was just a solid wing extruded from a sketch of the airfoil. It was 1m long with a chord of 35cm. The air velocity was set at 18 m/s. The computational domain was set much much larger than the model on the second try, which increased the force a bit but it's still only a quarter of what it should be.

I am unsure what you mean by numerical procedure; the force was found by inserting a global goal for the 'y component' of force, and the theoretical value was found using a lift calculation and checked with FoilSim.

Thanks
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Old   April 10, 2011, 23:45
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Quote:
Originally Posted by brianmcv View Post
Hi,
The geometry was just a solid wing extruded from a sketch of the airfoil. It was 1m long with a chord of 35cm. The air velocity was set at 18 m/s. The computational domain was set much much larger than the model on the second try, which increased the force a bit but it's still only a quarter of what it should be.

I am unsure what you mean by numerical procedure; the force was found by inserting a global goal for the 'y component' of force, and the theoretical value was found using a lift calculation and checked with FoilSim.

Thanks
The velocity that you have is very low, what is the angle of attack of the wing.
Is it possible for you to tell the application your wing is used and if you can look into the manual of Solidworks or their support to find what numerical procedure do they you it will be more helpful in finding the problem.
Raashid
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Old   April 11, 2011, 03:40
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The wing design is for an RC plane, which is why the speed is so low. The angle of attack is only 1 degree, as the airfoil selected is asymmetrical and generates lift at 0 angle of attack. The co-efficient of lift I'm getting from the CFD corresponds to an angle of attack of negative 6 degrees, so something is definitely off.

I will have a look for the numerical procedure and post back.

Thanks

Last edited by brianmcv; April 11, 2011 at 04:12.
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Old   April 11, 2011, 05:32
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Hello Brian,

Why do not you use XFLR5 instead. I am not familiar with Solid Works, but certainly at these reynolds numbers XFLR5 will give you much much more accurate results than any CFD software, unless you are at stall or have unconvenient geometry.

Are you running inviscid or viscous? If you are running viscous, then for this reynolds number CFD software will not account for separation bubbles and transition to turbulence.

You can download XFLR5 for free from the web.

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Old   April 11, 2011, 08:16
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Thanks truffaldino, I might give XFLR5 a shot if I can't get it to work in solidworks. The reason I'm doing it in Sworks as I want to use the data for other purposes within the program. It should be capable of reasonable accuracy, I read someone stating they got within 5% of measured values at just 10MPH.

I have no idea if its inviscid or viscous, pretty new to CFD! There doesn't seem to be an option to select either anywhere.
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