本研究以"有限元素法"模擬並分析高分子融 熔體之4:1直角收縮流動現象。流變模式採用里 歐諾夫(Leonov)黏彈流體模式。數值計算的結果包 括渦流範圍與渦流強度,以及速度、應力場分布, 並藉助文獻上之實驗數據以驗證其準確性。從模擬計算所得之流線與速度等值線分布可瞭解 高分子流體在收縮流場中所經歷之剪切和拉伸 流動;再配合文獻之拉伸黏度數據,分析探討渦流 現象與高分子流體拉伸行為之關係。另一方面, 以數值計算方法解全展流( fully developed flow)之速度、應力場,求得在不同剪率下之Weissenberg數,We 。本研究綜合分析不同剪率下渦流之變化,而求 得其與We及拉伸特性之適當關連性。 The finite element method has been utilized to analyze the 4:1 sudden contraction flow of polymer melts with the Leonov rheological model. Both the flow and stress fields were numerically simulated, and some experimental data from literature were obtained for comparisons. Moreover, the size and intensity of the vortex flow were predicted. The extensional and shearing characteristics of the contraction flow were made clear by inspecting the simulated streamline pattern and the absolute velocity contour plot. Flow behavior of polymer melts, when the continuous extension was encountered, was also studied by use of the available extension viscosity data. On the other hand, the Weissenberg number (We) at various shear rates was calculated by solving the fully developed flow field with the Leonov fluid model. Then, the appropriate relation of the vortex behavior in polymer contraction flow with We or with the extension feature can be successfully established.
第十五屆高分子研討會論文專集第八卷第一冊=Proceedings of the 15th ROC Polymer Symposium 1992 (I)