Abstract
射出過程中的充填階段其流體動力行為,一般可區分為一維發展主流及靠近流鋒處的複雜二維流.後者即所謂噴泉流動早期的模流分析以忽略波前區的特異性或以近似的模式來,模擬流體的充填流動.對於噴泉流動及運動方程式中的慣性項及暫態項的描述不能得到充分的滿足.特別是噴泉效應對分子排向性分佈晶度分佈及縫合線品質均有重要影響.因此在品質要求日趨嚴格的今天.本研究特別以整體統御方程式納入分析探討包括噴泉流在內的暫態含自由面的運動,特別注意波前區域的噴泉流動分析其對日後成型品的影響.本文採用標誌網格法並結合加權函數法(WeightingFunction Scheme)離散方程式.來避免高黏性流動的限制,適用於加工上的模擬.以SIMPLER流體整體統御方程式並藉由粒子的錯排達到追蹤流體軌跡的目的.由流動的分析結果顯示.本研究在一般含自由面的分析上均獲得滿意的結果.而在噴泉流的分析上預測牛頓流體及泛牛頓流體在二平板模穴的充填,並分析流場變化包括速度場壓力場的分佈情形.The Phenomenon of filling flow in injection molding can bedescribedin terms of an one dimensional fully-de- veloped mainflow and a complex two dimensional flow near the advancingfront, termed the" fountain flow ".In the early analysis offilling stage,different models have been proposed to describethe molding cycle with varying degrees of approximation. thesemodels, however, have generally neglected the melt frontregion,i.e.,the fountain effect and the transientand interialterms. Especally,the fountain effect is responsible for thehighly oriented surface layer and will influence the degree ofcrystallinity as well as the quality of welding line.Due to thesignficant implication for microstructure,the fountain effectis explicitly taken into considera- tion in the simulation. Acomputer program based on MAC method has been developed or thenumerical simulation of two dimensional viscous fluid flow.Especially,Weighting Function Scheme is employed to describethe governing equation which is solved by SIMPLER algorithm.Forparticle tracking,the phenomenon of steady,unsteady fluid flowwith a free surface flow can be described by numerical analysis. In this research,we observe "fountain effect" obviously inthe early stage of filling process,via the rearrangement of thevelocity profile in the vincinity of melt front. As the timegoing,front type changes and will not allow the steadyinterfacial type that corresponding to the predition inexperimental observation.