方柱绕流中聚乙烯熔体流变行为的数值模拟

采用了DCPP和S-MDCPP两种模型分别描述低密度聚乙烯熔体的本构行为。在迭代分步算法中引入了改进的有限增量微积分(FIC)法，并采用离散的弹性黏性应力分裂技术(DEVSS)/迎风流线(SU)法解决黏弹性流动分析中的对流占优问题。讨论了S-MDCPP模型预测的速度、压力及主链拉伸分布随Weissenberg(Wi)数的变化。结果表明，两种模型预测的速度、主应力差等色条纹和主链拉伸分布吻合较好；随Wi的增大，速度及压力均增大。

Numerical Simulation of Rheological Behavior of Polyethylene Melts Through a Square Cylinder

The constitutive behavior of low density polyethylene (PE-LD)were described by the DCPP and S-MDCPP models in this study. The modified finite increment calculus (FIC) procedure was introduced into the iterative fractional step algorithm, and the discrete elastic viscous stress split (DEVSS) and streamline upwind (SU) techniques were employed to cope with the convection dominated problem of the viscoelastic flow analysis in order to enhance the computational stability. It showed that the velocity, isochromatic fringe pattern of principle stress difference and backbone stretch distributions predicted by the DCPP and S-MDCPP models agreed very well.Moreover, the predicted velocity, pressure and backbone stretch distributions using the S-MDCPP model at different Weissenberg numbers (Wi) were discussed and it exhibited the velocity and pressure were enlarged with the increase of Wi.