I am simulating Fx 63-137 airfoil and it is a 2-D model. However, my solution is not getting converged. In the boundary conditions for inlet, I used components and 1xcosx6 (For x component) and 1xsinx6 for y component. Goes without saying this is for 6 degree angle of attack. My analysis is 2-D steady state and flow is inviscid. Chord length is 1m.

I tried to find the solution at 1e-3 convergence and I got it. While I tried 1e-6, the convergence is not happening even after 20,000 iterations.

And as I am simulating individually for different degree alphas, my convergence at 1e-3 was going okay from 0 to 8 degree angle of attack and these are all individual workbench projects for different alphas. Just as I started with 10 degree alpha, I wasn't able to converge the solution even at 1e-3 despite the 10,000 iterations. Why would that be?

Then I read somewhere I should try transient state simulation. I tried that and my solution was converged. May I get a good understanding of how transient state is able to converge my solution and how exactly does the time stepping is performed?

Also, I changed the Courant number and for Implicit formulation to 0.4, 1, 2 and 3 but again solution did not converge in steady state.

I guess I should stick to steady state but how to get the solution converged for those alphas that are beyond 8 degree? Please help me in convergence as this is very important for my project.

Besides, just need a confirmation if I am doing it all right. Once the solution is converged and I obtain the Cl and Cd, say for 6 degree alpha, I enter the following values

For Cd: x = 1 cos 6 and y = 1 sin 6.

For Cl, I enter, x = 1 sin -6, y = 1 cos -6.

And thus I get the Cl and Cd at 6 degree alpha. Velocity is obviously 1m/s here. Am I doing it right?