本文選題：非牛頓流體　切入點：微通道　出處：《天津理工大學》2017年碩士論文　論文類型：學位論文

【摘要】：近年來,隨著微流體芯片技術(shù)(Lab-on-a-chip)的不斷發(fā)展,利用微流體技術(shù)對微通道內(nèi)氣泡(液滴)的精準調(diào)控受到國內(nèi)外研究者的廣泛關(guān)注。相比流體體積法(Volume of Fluid,VOF),水平集法(Level Set)和VOF法耦合的(coupled level set and volume of fluid method,CLSVOF)能更加精準地捕獲氣液界面。本文利用CLSVOF法對微通道內(nèi)氣泡破裂及聚并進行數(shù)值模擬研究,研究結(jié)果可對微通道反應器的設(shè)計和氣泡流的精準操作提供理論依據(jù)。本文首先通過網(wǎng)格無關(guān)性分析及與實驗結(jié)果對比,驗證了該數(shù)值方法的有效性,然后選用廣泛應用于工業(yè)中的羧甲基纖維素鈉(CMC)水溶液為非牛頓流體,計算了微通道內(nèi)該流體中氣泡破裂和聚并行為。首先,對四條并行分岔微通道內(nèi)氣泡破裂行為進行研究,模擬結(jié)果表明:隨u_g/u_l增大,氣泡破裂后子氣泡依次呈現(xiàn)出長段彈狀流、彈狀流、泡狀流、不阻塞泡狀流四種流型;隨中間兩子通道寬度減小,其中氣泡流型由彈狀流轉(zhuǎn)變?yōu)榕轄盍?而兩側(cè)兩子通道由彈狀流轉(zhuǎn)變?yōu)殚L段彈狀流;隨子通道中間分岔角增加,中間子通道由長段彈狀流轉(zhuǎn)變?yōu)閺棤盍?而兩側(cè)子通道由彈狀流轉(zhuǎn)變?yōu)殚L段彈狀流;隨液相質(zhì)量濃度的增加,子通道氣泡流型出現(xiàn)較長彈狀流到彈狀流的趨勢。另一方面,當u_g/u_l≈1時,氣泡均勻破裂,當u_g/u_l增大時,中間子通道子氣泡較大;隨中間子通道寬度的減小,其中子氣泡明顯減小,而兩側(cè)子氣泡增大較快;隨子通道中間分岔角增加,中間子氣泡減小,而兩側(cè)子氣泡增大;隨液相質(zhì)量濃度的增加,氣泡破裂更為均勻。然后,對部分擴張微通道內(nèi)氣泡聚并行為進行計算,計算結(jié)果顯示:氣泡聚并概率隨擴張區(qū)域、液相流速、氣泡大小、液相質(zhì)量濃度的增大而增加,但隨氣泡間距的增加而減小;聚并時間隨擴張區(qū)域、液相流速、氣泡間距的增大而增加,但隨液相質(zhì)量濃度、氣泡大小的增大而減小。此外,不等大氣泡聚并結(jié)果表明:“小追大”情況往往會發(fā)生聚并行為,而相反“大追小”則出現(xiàn)二者排斥趨勢,不能發(fā)生聚并。
[Abstract]:In recent years, with the development of Lab-on-a-chip-chip technology, The precise control of bubbles (droplets) in microchannels by microfluidic technology has attracted wide attention from researchers at home and abroad. Compared with volume of fluid volume of fluid volume, horizontal set and VOF coupled coupled level set and volume of fluid method CLSVOF, the level set method can be more effective than the volume of fluid volume of liquid volume method. In this paper, CLSVOF method is used to simulate the bubble rupture and aggregation in microchannels. The results can provide a theoretical basis for the design of microchannel reactor and the accurate operation of bubble flow. Firstly, the effectiveness of the numerical method is verified by mesh independence analysis and comparison with experimental results. Then, the non-Newtonian solution of CMC (sodium carboxymethyl cellulose), which is widely used in industry, is used as non-Newtonian fluid to calculate the bubble rupture and coalescence behavior in the microchannel. Firstly, the bubble rupture behavior in four parallel bifurcation microchannels is studied. The simulation results show that with the increase of 渭 g / UL, the sub-bubbles show four flow patterns: long slug flow, slug flow, bubbly flow, non-blocking bubbly flow, and decrease with the width of the two sub-channels in the middle. The bubble flow pattern changed from slug flow to bubble flow, while the two sub-channels on both sides changed from slug flow to long slug flow, and the intermediate sub-channel changed from long slug flow to slug flow with increasing bifurcation angle in the middle of sub-channel. On the other hand, with the increase of mass concentration of liquid phase, the bubble flow pattern of sub-channel shows a trend of longer slug flow to slug flow. On the other hand, when uSGP / UL 鈮，

本文編號：1581417