Hi all. In Fluid dynamics, is vorticity equiavlent to angular momentum? It seems that vorticity is twice of the rate of rotation of a fluid element at a point, and angular momentum is the density times the rate of rotation of a fluid element, so they just differ by some constant? But it is a bit strange to me... I know the the rate of rotation of a fluid element is proportional to shear stress in fluid dynamics. So shear stress gives rise to rate of rotation of a fluid element and hence angular momentum of the element. But from physics, the presence of shear stress (think of force) shall give rise to "rate of change of angular momentum", isn't it? So...which is the correct one? Shear stress just give angular momentum or rate of change of angular momentum? Please kindly explain.