THE KENICS STATIC MIXER - A 3-DIMENSIONAL CHAOTIC FLOW

The Kenics static mixer was investigated numerically using Lagrangian methods to characterize mixer performance for low Reynolds number flow s. Particle tracking simulations were used to compute residence time d istributions, striation evolution, and variation coefficient as a func tion of the number of mixer elements. The mixing measures calculated f rom the numerical simulation agree closely with reported experimental results from the literature. Stretching of material elements in the mi xer flow was also computed. The average stretching of material element s increased exponentially with the number of periodic mixer segments ( a signature of chaotic flows). The probability density function of the logarithm of stretching values, H-n(log(10)lambda), had a Gaussian di stribution over the central spectrum of stretching intensities, with n o deviations from the Gaussian profile at low stretching intensities, suggesting a globally chaotic flow. A significant tail of high stretch ing intensities was found. The spatial locations of points with the hi ghest stretching values corresponded to the manifolds of two period-1 hyperbolic points present in the flow. (C) 1997 Published by Elsevier Science S.A.