4WS转子密炼机聚合物混沌混合的拉格朗日拟序结构分析

Lagrangian Coherent Structure Analysis of Chaotic Mixing in an Internal Batch Mixer with 4WS Rotors

采用拉格朗日拟序结构的分析方法,对标准四棱4WS转子密炼机聚合物混沌混合进行研究。利用网格叠加技术(MST),计算了密炼机二维流场的速度场分布。在此基础上,利用基于拉格朗日体系的有限时间Lyapunov指数(FTLE)、拉格朗日拟序结构(LCS),结合Poincaré映射和粒子可视化技术,分析了4WS转子密炼机二维流场的混沌混合特性;讨论了转子几何结构对FTLE和LCS分布的影响以及密炼机二维流场潜在的动力学和几何特性。结果表明,由于物质线的封闭状态,导致了密炼机近转子区流体输运受到了阻碍,因此,增强近转子区与远转子区的物质交换是进行转子优化的重要环节。由于4WS转子棱边独特的凹槽结构,在近转子区易产生马蹄形结构,在流域中形成同宿穿插结构,增强了近转子区和远转子区之间的物质交换,强化了密炼机流场的混沌混合。

Mixing mechanism in a 4WS batch internal mixer was studied with Lagrangian coherent structure （LCS） analysis. Two-dimensional velocity distributions in the mixer were calculated with mesh superposition technique （MST）. Moreover, the characteristics of chaotic mixing in the mixer were analyzed based on finite-time Lyapunov exponent （FTLE）, LCS, Poincar6 map and particle visualization technology. The effects of rotor geometry on FTLE and LCS distributions were discussed. Furthermore, potential dynamics and geometrical features in the mixer were given. The results show that fluid transportation is hindered by the closed material line near the rotor region. Therefore, it is important to enhance fluid exchange between near and far rotor areas. In addition, Smale horseshoes near rotor region is easily formed due to special structure of rotor edges, which leads to homoclinic transverse that enhances material exchange and chaotic mixing in the mixer.