液體黏滯性對雙液滴碰撞之影響：以甘油與奈米水溶液為例

On the viscous effect in binary droplet collision using glycerol solutions and nanofluids

洪誌隆(Chih-Lung Hung)

指導教授 ： 潘國隆

國立臺灣大學/工學院/機械工程學研究所/碩士(2015年)

https://doi.org/10.6342/NTU.2015.01660

摘要

本研究首先以雙液滴碰撞為主軸，以黏滯效應對於彈開及分離機制為研究重點，利用閃頻儀同步的方法我們可以在高解析度的情況下觀察出液滴碰撞的時序圖，並且以不同重量百分濃度的甘油水溶液以及利用官能化(functionalized)方法製備的二氧化矽奈米水溶液當作實驗流體研究雙液滴碰撞行為。
研究結果發現液滴碰撞型態共可分為六大區域，分別為(I)液滴輕微變形後結合(coalescence after minor deformation)、(II)碰撞彈開(bouncing)、(III)液滴顯著變形後結合(coalescence after substantial deformation)、(IV)反射分離(reflexive separation)、(V)拉伸分離(stretching separation)和(VI)旋轉分離(rotational separation)。在研究中我們發現藉由增加甘油水溶液之濃度，最終可以在正撞區域發現碰撞彈開現象，並利用前人提出的模型提出關於甘油水溶液的拉伸分離邊界預測關係式，並驗證當歐式數大於0.04時，黏滯性將主導液滴碰撞結合的過程，使正撞彈開之臨界韋伯數不再呈線性增加，而在濃度很小時其奈米溶液的碰撞行為與水表現一致，當濃度增加會因界面效應導致分離有延後發生的情形。

關鍵字

同步 ； 液滴碰撞 ； 甘油 ； 黏性效應 ； 奈米粒子

並列摘要

The viscous and nanoparticle effect on droplet-droplet collision behavior at ambient conditions were studied experimentally. Glycerol solutions and silica nanofluids were used as working liquid providing viscosities in the range from 0.93 to 15.94 mPa•s. The droplet image and collision history were recorded on a video recorder by using a strobe light synchronized with the droplet generator with various phase differences.
The collision outcomes in terms of Weber number and the impact parameter could be categorized into six distinct regimes: (I) coalescence after minor deformation, (II) bouncing, (III) coalescence after substantial deformation, (IV) reflexive separation, (V) stretching separation and, (VI) rotational separation. It is shown that, by varying the viscosity of the glycerol solution through its concentration, the border between bouncing and coalescence were shifted toward lower impact parameter until bouncing appears on head-on with increasing viscosity and verified empirical correlation for the onset of reflexive separation for high viscosity fluids. Furthermore, it was found the collision behavior of 1% weight percentage concentration nanofluids was the same with water and separation occurred at higher Webber number with increasing concentration.

並列關鍵字

synchronized ； droplet collision ； glycerol ； viscous effect ； nanoparticle

參考文獻

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