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本文利用罚有限无法 ,采用幂律本构模型 ,对聚合物熔体在矩形收敛口模内的三维等温流动进行了数值模拟。对于幂律模型 ,即使流量非常大 ,经过有限次迭代 ,计算都能够收敛 ,并得到合理的结果。流量越大 ,则主流动方向的流速从流道入口至出口加速上升的趋势越明显。在流道中心呈现拉伸流动 ,而壁面附近则为剪切流动。流道的中心部位存在比拉伸应力更大的第一法向应力差。在同一横截面上压力并不相同 ,因此以往关于在同一横截面上的压力恒定的假设是不恰当的。采用罚有限元法 ,速度场很小的误差就可能导致压力求解较大的误差 ,而且在流道壁面附近这种误差表现得特别显著 ,因此用罚有限元方法求解压力场有较大的局限性。
In this paper, we use the power-law constitutive model to simulate the three-dimensional isothermal flow of polymer melt in a rectangular convergent orifice by using the penalty of the penalty. For the power-law model, the calculation can converge and obtain reasonable results even after a very limited number of iterations, even though the flow rate is very large. The greater the flow, the main flow direction of the flow from the entrance to the outlet accelerated the trend of the more obvious. In the center of flow channel presents stretching flow, while the wall near the shear flow. There is a first normal stress difference greater than the tensile stress at the center of the flow channel. The pressures are not the same on the same cross-section, so the previous assumption about a constant pressure on the same cross-section is not appropriate. With the penalty finite element method, the error of small velocity field may result in a large error of pressure solution, and this error appears particularly prominent near the flow channel wall. Therefore, using the penalty finite element method to solve the pressure field has a great limitation Sex.