晶格波茲曼法(Lattice Boltzmann method, LBM)是近年來盛行的計算方法。微粒子特性背景使得在晶格波茲曼方法在模擬雙相流領域中具有許多其他過去數值方法所沒有的獨特優點。基於上述的原因，本文利用二維晶格波茲曼法之多種成份流模型，探討在微流體聚焦裝置中，兩不互溶流體同時注入十字型微流道中之微乳化液滴生成系統其液滴生成形態。由於Shan & Chen模型將兩不互溶流體交互作用力直接併入粒子之間，在模擬兩不互溶流體交會時，粒子間交互作用力只考慮離關注粒子之最近的粒子。因此粒子間距在此問題顯得格外重要，本文亦針對不同網格間距對液滴破裂現象影響測試。計算結果顯示，當兩不互溶流體所對應之表面張力越小，生成的液滴半徑和兩液滴之間距也隨之越小。另一方面，在固定非連續相入口流速時，提高兩相入口流速比情況下，產生的液滴半徑也較小。因此，在相同微流體聚焦裝置下，非連續相入口流速與兩相入口流速比，控制了生成液滴的形態與大小。綜合模擬結果，本文總共歸納出三種微流體聚焦裝置流場形態，分別為平行流、穩定生成液滴、和不穩定生成液滴。

Lattice Boltzmann method (LBM) is a popular computational method in recent years. The characteristic of microscopic particles makes it own good ability to simulate two-phase flow and differs from the traditionally developed numerical method. Based on the above reason, this study investigates droplet formation in a flow-focusing device using LBM. We used a two-dimensional multi-component LBM to simulate two immiscible fluids injected into a cross-junction micro-channel. The cross-junction channel is used to form micro-droplets in the liquid-liquid system. In this study, Shan & Chen’s lattice Boltzmann model for two-phase flows, is adopted to treat molecular interaction force among two particles. This model only considered the interaction force between the nearest neighbor grid points. Therefore, we have to test grid sizes between the particles for the effect on the drop breakup phenomenon. The computation results showed that, as the surface tension was decreased, the droplet size and the interval between two generated drops were decrease. Besides, when the flow rate ratio was increased under a fixed boundary condition of the velocity of the dispersed phase flow, the droplet size was decreased. The droplet shape and size in the flow-focusing device were could be formed by different flow rate ratios and velocities of the dispersed phase flow. This study illustrated the drop size as a function of flow rates, flow rate ratio and surface tension of the two immiscible fluids.
Finally, we observed that there are three types of the flow phenomenon in this study, namely, parallel-flow, stable droplet flow, and unstable droplet flow, respectively.

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