# Negative lift in Modeling an airfoil design for wind turbine

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 July 23, 2012, 13:05 Negative lift in Modeling an airfoil design for wind turbine #1 New Member   Ram N Bishnoi Join Date: Jul 2012 Posts: 2 Rep Power: 0 Sponsored Links Hello, I am trying to model a airfoil design for wind turbine in fluent. Chord length of airfoil is 0.3m and angle of attack is 8deg. But I am getting negative value of lift coefficient. I already checked boundary conditions and all. Please suggest.

 July 25, 2012, 02:25 #2 New Member   Ram N Bishnoi Join Date: Jul 2012 Posts: 2 Rep Power: 0 Thanks Mr. Dargahi, The problem consists rotation of 2D airfoil from 0 to 180 degree, means changing angle of attack. I am using wind velocity 5m/s and considered inviscid viscous model. In setting...I have confusion that during changing angle of attack should I have to change velocity component in boundary condition? and what about the reference values? In meshing also I have a slight confusion as I am using unstructured triangular grid with enough nodes to model turbulence. Please suggest.

July 27, 2012, 08:35
#3
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duri
Join Date: May 2010
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Quote:
 Originally Posted by Ram209e Thanks Mr. Dargahi, The problem consists rotation of 2D airfoil from 0 to 180 degree, means changing angle of attack. Please suggest.
Is this a transient problem of oscillating airfoil?.

August 8, 2012, 22:39
#4
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Jos
Join Date: Jun 2012
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Quote:
 Originally Posted by Ram209e Thanks Mr. Dargahi, The problem consists rotation of 2D airfoil from 0 to 180 degree, means changing angle of attack. I am using wind velocity 5m/s and considered inviscid viscous model. In setting...I have confusion that during changing angle of attack should I have to change velocity component in boundary condition? and what about the reference values? In meshing also I have a slight confusion as I am using unstructured triangular grid with enough nodes to model turbulence. Please suggest.
Hi Ram;

With respect to the angle of attack, i guess you could obtain the cosine and sine values accordingly in the boundary condition for velocity input and the reference value(i.e. area) for a 2D case would be 1 ( i.e.chord length) but if for a 3D case then we would need to take into consideration the extruded length of airfoil in the third direction....Hope this helps...

Last edited by joseph@CFD; August 8, 2012 at 22:54.

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