question setting up airfoil Boundary Conditions
 

Hi I am going through the tutorial from http://courses.cit.cornell.edu/fluent/airfoil/step4.htm


Was wondering if anyone could expand on the reason why you adjust the angle of attack of the airfoil. The reason given is "due to the error caused by assuming the airfoil to be 2D instead of 3D."

Also how do did they decide the size of the error?

below is the section taken from the tutorial :

Define > Boundary Conditions
Set farfield1 and farfield2 to the velocity-inlet boundary type.
For each, click Set.... Then, choose Components under Velocity Specification Method and set the x- and y-components to that for the freestream. For instance, the x-component is 50*cos(1.2)=49.99. (Note that 1.2° is used as our angle of attack instead of 2° to adjust for the error caused by assuming the airfoil to be 2D instead of 3D.)

Thanks