Slip boundary condition
 

Hi every body

I'm solving inviscid flow over Naca0012 airfoil using a control volume based finite element method! I'm using slip boundary condition at wall.
I've used two method for applying wall boundary condition:
1) at wall the mass fluxes are zero so the continuity equation doesn't change!
for x and y momentum equations the pressure fluxes for the wall are added to the equations. For x-mom equation integral(p.ds_x) is added and for y-mom equation integral(p.ds_y) is added.

2) at the wall I have transfered the x and y mom equations to the normal and tangential directions at the wall, It means that I've replaced the x-mom with this equation:
(alfa is the local angle of the surface)
in tangential direction: Mom_x.sin(alfa)-Mom_y.cos(alfa)=0

and I've replaced the y-mom with this equation:
in normal direction: u.cos(alfa)+v.sin(alfa)=0

but unfortunately in both cases my code didn't converge!I have solved the code for viscous flows and it works. I think, maybe there is something wrong with wall boundary condition.
Does anybody have any idea about that? Is there something wrong with my boundary condition?

Thanks in advance