Abstract In the present study, the polymer crystal growth under the flow field is numerically simulated by using a coupled phase field (PF) and lattice Boltzmann (LB) method. Firstly, the phase field method is presented to capture the growth interface of polymer crystals, including the common morphologies of spherulite and shish-kebab crystallites. Then the lattice Boltzmann method is introduced to solve the viscous non-Newtonian flows of the polymer melt, where the half-way bounce back boundary condition is imposed with the aid of shape level-set (LS) function which is used to represent the crystal interface at each time. At last, the crystal growth for spherulites and shish-kebab crystallites under flow field is simulated by using the coupled PF–LB method, where the cross-WLF model is chosen to describe the melt viscosity. The effects of the flow velocity on the crystal morphologies, including single and multiple spherulite and shish-kebab crystallites, are analyzed in detail. The numerical results show that the flow velocity has an important impact on the crystal morphologies, and the crystals grow more faster towards the upstream direction, especially in the single and multi spherulites growth process.

中文翻译：

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使用耦合相场和晶格 Boltzmann 方法的流场下聚合物晶体生长的数值模拟

摘要 本研究采用耦合相场（PF）和晶格玻尔兹曼（LB）方法对流场下聚合物晶体的生长进行了数值模拟。首先，提出了相场法来捕获聚合物晶体的生长界面，包括球晶和烤肉串微晶的常见形态。然后引入格子Boltzmann方法求解聚合物熔体的粘性非牛顿流动，其中借助用于表示晶体的形状水平集（LS）函数施加中途反弹边界条件每次界面。最后，使用耦合PF-LB方法模拟流场下球晶和烤肉串晶粒的晶体生长，其中选择cross-WLF模型来描述熔体粘度。详细分析了流速对晶体形态的影响，包括单个和多个球晶和烤肉串微晶。数值结果表明，流速对晶体形貌有重要影响，晶体向上游方向生长得更快，特别是在单球晶和多球晶生长过程中。