應用面追蹤法模擬突縮微流道內氣泡的運動

Abstract

本研究利用面追蹤法(front-tracking method)數值模擬氣泡的動態，應用的程式原為二維軸對稱，這裡將其改為二維，與原版不同的地方是，此版本可設置多顆氣泡並且可以模擬非軸對稱的物理現象。 本文分成兩個部分，第一部分，模擬史拉格氣泡(bubble slug)在壓力驅動的管流中，通過在雙側擺放障礙物之突縮流道，以無因次化後之主要無因次化參數Re、We為變因，探討氣泡可否通過障礙物與通過障礙物時的情況，第二部分，我們將探討多氣泡之間的交互作用，由於在壓力驅動的管流中，多氣泡交互作用並不明顯，多氣泡研究著重在上升氣泡的案例，同樣地，藉由改變上升氣泡的無因次化參數，研究其上升軌跡、形狀、尾流之間的交互影響和牆壁效應(wall effect)對氣泡行為的影響。

This research shows the simulation results of bubble dynamic using a front-tracking method. The applied code was modified from 2D axisymmetric version to 2D version. Compared with the original version, this version can set many bubbles or droplets in the domain, and we can present the phenomenon which was non-axisymmetric. This paper consists of two parts. The first part discusses bubble dynamics in a microchannel with sudden contraction. A Bubble slug was placed in a microchannel with sudden contraction which has a fixed pore size. In a pressure driven flow, this bubble slug will pass through or be held back by a bilateral block due to varied dimensionless parameters, Reynolds number and Weber number. Also, with the different parameters, bubble slug will deform in distinct way. In the other part, we want to present the interactions of multi-bubble dynamics. Thanks to the bubble behavior was confined by the pressure driven flow, the interaction of bubbles was not sufficiently obvious. We differ our focus to a pair of rising bubble which was lined in a row, then, we can observe the interaction of bubbles clearly. Likely, By differing the dimensionless parameters of rising bubble, there were some interesting phenomenon on bubble shape, rising trajectory and the wake behind bubbles. We also discussed the wall effect by putting the bubbles in a narrow or broad domain.