Lagrangian angular momentum vortex definition and tracking

In the present paper, we study transport properties of coherent vortices. These structures are formed by tubes of fluid parcels that complete similar material rotation. Here, we demonstrate that time $t_0$ positions of such physical structures can be identified from the angular momentum along their trajectories. We identify and extract these Lagrangian vortices as material domain in which fluid elements complete similar Lagrangian angular momentum around the same axis and over the same finite time duration. The present method shows high vortices' monitoring capacity by identifying automatically all coherent clockwise and counterclockwise vortices. The performance of the proposed method is illustrated over different two- and three-dimensional flows.