Chaotic mixing hyperbolic points

At the same time Chien, Rising, and Ottino (17) studied chaotic flow in two-dimensional cavity flows with a periodic moving wall, which is relevant to mixing of viscous polymeric melts. All two-dimensional flows, as pointed out by Ottino (18), consist of the same building blocks hyperbolic points and elliptic points. A fluid particle moves toward a hyperbolic point in one direction and away from it in another direction, whereas the fluid circulates around parabolic points, as shown in Fig. 7.12. 

Fig. 7.14 Elliptic and hyperbolic points in Fig. 7.13(d). Circles represent elliptic points, and squares, hyperbolic points. [Reprinted by permission from J. M. Ottino, C. W. Leong, H. Rising, and R D. Swanson, Morphological Structures Produced by Mixing in Chaotic Flows, Nature, 333, 419 125 (1988).]...

The experiments also demonstrated presence of the mixing islands , where very little mixing took place. In consequence, the chaotic mixing could be schematically represented by the streamline diagram comprising the elliptic points located in the center of the blinking vortex and a hyperbolic... 

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