I'm trying to implement a new
 

I'm trying to implement a new interpolation scheme (first order with flux splitting) and to understand how this is done in openFOAM I'm trying to decipher how the the basic first order upwind is implemented, without much success.

In the upwind.H file I understand the limiter is set to zero. However it's not clear to me how the weights() method work: it returns pos(this->faceFlux_), but I don't get where/how the actual flux is calculated.

Any hint on this topic would be of great help.

Regards,
Alberto