Simple Question Regarding Symmetry Planes

Atella · April 9, 2010, 10:59

Hi,
Simple question i hope...

I am looking at the flow around an airfoil and i used a symmetry plane down the centre of the wing in order to reduce computational time.

When it comes to working out the CL of the wing i obtain my z-force using CFX and using CL=L/0.5*rho*v^2*A calculate CL.

My question is what is the area is use? I know it has to be the planform area however as i used a symmetry plane is the area now HALF as the symmetry plane cuts the wing in half, or has the CFD taken this into account and the area is the full plan area.

Thanks

ghorrocks · April 10, 2010, 06:40

Symmetry planes have no effect on volume or surface integrals, or global balances or flow rates either for that matter. So if you use the area()@ function it will just be the area of the meshed region, and the force()@ function will just return the force of the meshed region.

Atella · April 10, 2010, 08:43

Thanks for that, so to work out the force on the whole wing is it 2x the area of the meshed region, considering the meshed region is half a wing.

Cheers

ghorrocks · April 11, 2010, 06:44

Yes, you would have to double the force reported.

April 9, 2010, 10:59	Simple Question Regarding Symmetry Planes	#1
Atella New Member Join Date: Jan 2010 Posts: 8 Rep Power: 16	Hi, Simple question i hope... I am looking at the flow around an airfoil and i used a symmetry plane down the centre of the wing in order to reduce computational time. When it comes to working out the CL of the wing i obtain my z-force using CFX and using CL=L/0.5rhov^2*A calculate CL. My question is what is the area is use? I know it has to be the planform area however as i used a symmetry plane is the area now HALF as the symmetry plane cuts the wing in half, or has the CFD taken this into account and the area is the full plan area. Thanks

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April 10, 2010, 06:40		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,695 Rep Power: 143	Symmetry planes have no effect on volume or surface integrals, or global balances or flow rates either for that matter. So if you use the area()@ function it will just be the area of the meshed region, and the force()@ function will just return the force of the meshed region.

April 10, 2010, 08:43		#3
Atella New Member Join Date: Jan 2010 Posts: 8 Rep Power: 16	Thanks for that, so to work out the force on the whole wing is it 2x the area of the meshed region, considering the meshed region is half a wing. Cheers

April 11, 2010, 06:44		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,695 Rep Power: 143	Yes, you would have to double the force reported.