Correct surface normal velocity?
 

I wanted to create fixed normal velocity BC on a curved surface (flow outwards the domain), but matching options don't seem to behave according to their descriprion.
I use openfoam.org 7 version, and there are 2 BCs i tried to use:
surfaceNormalFixedValue
surfaceNormalUniformFixedValue

I don't think I understand what is the difference between them, but according to their description they both should provide Umagnitude*normalVector values on a given patch.


I expect fixed 1.5 m/s velocity magnitude pointed outwards the domain, but the total magnitude is much larger, because surface tangent velocity component doesn't seem to be fixed [PICTURE ATTACHMENTS]. When you look at the points on my curved surface aligned with X axis they should have zero Ux components, but they clearly don't.

My computations seem to act stable, calculation ends at ~1133 iterations.


Is there any way to fix this? I expect no tangent component or at least very small tangent component.

I used groovyBC from swak4foam with:
It worked for me, but I'm aware that not everybody uses groovyBC.