A novel kind of dual-speed corotating non-twin kneading elements with a zero stagger angle is designed to improve mixing ability. The physical model considering several narrow gaps is developed where the inlet and outlet transition sections are also included. Finite element method associated with the mesh superposition technique is further applied to solve the time-dependent flow field where fluid is assumed to obey the Carreau constitutive model. The tracers initially from different locations are tracked using a self-developed fourth-order Runge–Kutta scheme. Distributive mixing is evaluated through evolution of tracer droplets and decaying of variance index with time. In addition, a Lagrangian statistics method is used to characterize the dispersive mixing in terms of the statistical distributions of mixing index and their integration areas within the range of mixing index larger than 0.5. In contrast, the kneading elements of a conventional twin screw configuration are also modeled to show the mixing difference.

中文翻译：

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拉格朗日统计法双速同向旋转非双螺杆捏合元通道混合的数值表征

设计了一种新型零交错角双速同向旋转非双捏合元件，以提高混合能力。开发了考虑多个窄间隙的物理模型，其中还包括入口和出口过渡部分。进一步应用与网格叠加技术相关的有限元方法来求解假定流体服从Carreau本构模型的瞬态流场。使用自行开发的四阶 Runge-Kutta 方案跟踪最初来自不同位置的示踪剂。通过示踪液滴的演变和方差指数随时间的衰减来评估分布混合。此外，采用拉格朗日统计方法，在混合指数大于0.5的范围内，根据混合指数的统计分布及其积分区域来表征分散混合。相比之下，传统双螺杆配置的捏合元件也被建模以显示混合差异。