• 作者： Wang, Yeh
• 中文摘要： 黏塑性流體係重要之非牛頓流體在工業界有廣泛之應用。雖然關於非線性賓漢流體之流動模式甚多, 然而並無詳細比較。本研究係針對常用之三種模式, 即Herschel-Bulkley模式、Papanastasiou模式、與雙黏度模式, 進行深入之比較與討論。研究所方法係應用變分積分之最小化, 並解出橢圓形流道內之流場, 及通過突縮管與流出管外之自由面流動。一般而言, 由三種模式所預測之流場均甚為接近, 而如果能夠恰當選擇此等模式之流變參數, 則均能預測在降服面之剪速率張量會呈急遽變化, 並可據以決定降服面之位置。
• 英文摘要： A comparative evaluation of existing rheological models is provided for yield-stress fluids through extrusion dies. Three viscoplastic models are compared: the regularized Herschel-Bulkley model, the bivisosity model, and Papanastasiou's model. The continuous modification of the original discontinuous model makes the direct minimization of the variational integral possible. The analysis is applied to fully developed flow in an elliptical duct and a two-dimensional extrusion flow. It is shown that in the steady extrusion flows the flow behaviors predicted from various models are similar to one another regardless of their different forms. Through proper choice of the material parameters, sharp transitions in the distributions of the second invariant of the shear rate tensor II.gamma. are predicted from all three models, making the unambiguous determination of the position of yield surfaces possible.
• 中文關鍵字： 非線性黏塑性流體; 變分積分; 賓漢數; 非圓形管道; 自由面流動
• 英文關鍵字： Nonlinear Viscoplastic Fluid; Variational Integral; Bingham Number; Noncircular Duct; Free Surface Flow