Hello,

does anybody know a reference for the derivation of the Navier-Stokes eqs in duct with variable cross-section?

Thanks,

Zsolt.

what type of duct, straight circular/ rectangular?

I am interested in Navier-Stokes equation including variable cross section for straight rectangular duct.

Thank you

generally, for ducts of varying cross section in the streamwise direction (eg convergent or divergent ducts), you have to introduce a new boundary-fitted coordinate system (normally non-orthogonal) and then recast the NS eqs (in cartesian , cylindrical coordinate, etc)into this new coordinate.