The motion of point P' relative to neighboring point P is
given by .
Take the velocity derivatives tensor A apart into symmetric and antisymmetric parts:
The symmetric part is called the strain-rate tensor. By rotating the coordinate system, to x',y',z', it becomes diagonal:
The asymmetric part corresponds to solid body motion:
Vorticity is important: when there are no viscous effects, no vorticity will be generated.
The line integral of the velocity along a closed contour is called the
circulation of that contour:
Exercise:
What can you say aboutif
?