[Navier Stokes] Upwinding of transporting velocity
We at some point also discussed if we wand to do upwinding also for the transporting velocity. I think it might be better to upwind both factors of the advective term. I think that would involve upwind decisions self versus opposite for the integrals along the frontal faces and upwind decisions inside versus outside velocity lateral for the integrals along the lateral faces. For the upwind decision self or opposite, it would be based on (self+opposite)/2. For a upwind decision inside versus outside, I could imagine basing the decision on self+parallel/2.