Computational study of chaotic mixing in co-rotating two-tipped kneading paddles: Two-dimensional approach

This study attempts to investigate the kinematics of the mixing occurring in the lenticular kneading disc section of the co‐rotating twin screw extruder, employing the tools of dynamics. The Eulerian velocity field distributions, generated by a two‐dimensional isothermal and creeping flow of Newtonian fluid under the periodic co‐rotation of the kneading discs, were obtained by Finite Element Method. A simple and novel particle tracking technique based on the FEM solution of the velocity field was employed to follow individual particles, and to produce the Poincare section mapping. Furthermore, fingerprints of chaotic motion were revealed essentially through the Lyapunov exponents, which were positive. The results suggest that the dynamics in the two‐dimensional kneading disc section of the twin screw extruder can be characterized as capable of imparting chaotic motion. The tools developed in this study should facilitate a better understanding of the mixing capabilities of the twin screw extrusion process.