Enhancement of Laminar Flow and Mixing Performance in a Lightnin Static Mixer

Abstract The laminar chaotic flow and mixing performance of a high-viscosity fluid in Lightnin static mixers (LSM) was numerically investigated via a Lagrangian particle method based on the Particle tracking technique in the range of Re =0.1−100. The numerical results of Z factor have a good agreement with the reported data from the literature. With the increase of Re in LSM, the Darcy friction coefficient values decrease and the product of f D · Re linearly increases. With the same aspect ratio ( A r ), the product of f D · Re in LSM is higher by 36−57 % than that of KSM. The distribution evolution of circular group of massless particles is successfully investigated by particle distribution uniformity (PDU) in the first few mixing elements. A new ideal distribution model is proposed for structure radius (SR) which is successfully used to investigate uniform distribution of mixing process in the last few elements. The effects of Re and A r of mixing elements on dispersive mixing performance are characterized by extensional efficiency and stretching rate. The logarithms of geometrical average stretching rate of massless particles increase linearly with the number of mixing elements. The stretching rate in LSM with A r =1, 1.5, 2 is average higher by 45.91 %, 36.05 % and 24.32 % than that of KSM with A r =1.5. As far as the creeping flow in LSM is concerned, the logarithm values of stretching rate are independent of Re and A r . The mixing performance factor η is proposed to evaluate the enhancement mechanism of mixing performance based on the energy consumption. The η increases with the increasing Re and decreasing A r . The profiles of η indicate that the mixing enhancement ability of LSM is better than that of KSM.