聚合物熔体矩形流道挤出胀大的数值模拟

运用Picard迭代格式的有限元方法，采用Wagner积分型本构方程对黏弹流体挤出胀大进行三维模拟分析。每次迭代根据新的自由面边界位置重新划分网格，由前一次迭代得到的速度场，算出单元高斯点流线，沿流线积分计算应力，把应力作为拟体力，建立非线性方程组迭代格式。对不同宽度和长度的矩形流道的挤出胀大进行模拟计算，分析了流道宽度和长度对胀大率的影响，结果表明，随着宽厚比的增加，厚度胀大率随之增加，随着流道长度的增加，胀大率逐渐下降。并把结果与二维狭缝流道的数值模拟和实验结果相比较, 结果表明，用该方法对黏弹流体挤出胀大流动进行三维模拟是可行的和准确的。

Numerical Simulation of the Extrudate Swell of Polymer Melt Through Rectangular Die

In this paper, the finite element method of Picard iterative format was applied for analyzing three-dimensional extrudate swell of viscoelastic fluid flows using Wager integral constitutive equations. During each iteration, the updated streamline of boundaries was generated according to boundary condition of velocity. The streamline of Gauss point was acquired according to the velocity field of previous iteration. The stress was treated as pseudo-body and the format of iteration was given. Extrudate swell of different width and length of the rectangular die were analyzed. Results of swell ratios influenced by width and length of die were shown. It showed that the swell ratio increased with increasing ratio of width to thickness, and decreased with increasing length of runner. The results were very accurate and were compared with two dimension solutions and experiment. It proved that this method was efficient and reliable.