CFD Online Discussion Forums - Moving airfoil with constant speed: boundary conditions

Hi all

I am trying to simulate a moving airfoil with constant speed (Mach=0.755, $\ \alpha$ =1.25). I have two boundary conditions:

1. Farfield
2. Slip wall (airfoil)

For all faces I gave face velocities as:

$\ vbx = -Mach \cos (\alpha)$
$\ vby = -Mach \sin (\alpha)$

Also satisfying GCL condition.

At the farfield, I set

$\ (\rho,u,v,p) = (1, 0, 0, \frac{1}{\gamma})$

where $\gamma$ is the ratio of specific heats.

For slip wall I set velocity as the tangential velocity of the neighbor near boundary cell.

The flow is initialized with zero (u,v) everywhere. But with these boundary conditions residual is zero so there is no point to iterate. So how should be the proper boundary conditions?