plunging airfoil

Quarkz

i've just implemented the ALE formulation to my 2d FVM NS code which uses fractional step. i'm trying to simulate flow past a plunging airfoil, in this case moving up with a slowly increasing vertical velocity up to u(y)=0.5. ie the mesh moves up with this velocity

At Re=100, the ans i get is a resulting flow field which has 0<u(y)<0.5, most >0.3 except near the airfoil. At the leading edge, the flow is pushed down. Is this a logical ans? however, at Re=1000, the ans diverges.

My BC is u(y)=0.5 at the top/bottom/front of my c-grid (besides the standard u(x)=1.). u(y)=0.5 at the top/bottom surface of the airfoil. Is this correct?

I get a feeling that the airfoil is pushing the flow up on the top surface hence u(y)=0.5. however, at the airfoil's bottom, should the flow be at u(y)=0.5 ie same as airfoil's surface's speed?

in using the ALE formulation, all i've done is to add the mesh velocity into the fractional step, modify the BC to have the outer edge of the c-grid & inner boundary to follow the mesh speed, ie u(y)=0.5. Is that all there is to it? Did i miss out something?

thanks