I didn't do this kind of stuff, but what I think the best way is to check 1) whether N-S equation or any other equation you want to use for momentum balance of fluid assume constant viscosity or not. Seems to me that NS equation can be used for non-homogeneous or non-constant viscosity problems 2) re-derive the vorticity equation by taking curl to the momentum equation and find out which terms the viscosity will go in 3) take simple senarios, find out solutions such as shearing flow
Vorticity is generated due to shear stress, which viscosity plays a crucial role. If the two flow has a velocity gradient, then vorticity could be generated. Just my two cents.
【在 g****d 的大作中提到】 : Vorticity is generated due to shear stress, which viscosity plays a crucial : role. If the two flow has a velocity gradient, then vorticity could be : generated. Just my two cents. : : 大 : 式