Negative lift in Modeling an airfoil design for wind turbine
 

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.

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.

Is this a transient problem of oscillating airfoil?.

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...