stream function and vorticity

[manav...@gmail.com]

sir

will deriving the momentum equaton we have taken into account of only symmetric part of velocity gradients over different surfaces and ignored the anti symmetry part of velocity function the rotational part was considered to be zero but while deriving the vorticity stream function we consider the rotational part in deriving the momentum equation which doesnt have any rotional part how did we arrive in getting rotational gradient with symmetrical gradients please if you could explain