Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/1769
標題: 液滴形成的流體特性模擬
Simulation on the Fluid Characteristics of Micro-drop Formation
作者: 林俊偉
Lin, Chun-Wei
關鍵字: Micro-droplet;微型液滴;volume of fluid,;two-phase flow;流體體積法(VOF);二相流
出版社: 機械工程學系所
引用: 1. Plateau, J., 1873, ”Statique Experimentable et Theorique des Liquids Soumie aux Seules Forces Moleculaire”, Vol.1, 2, Paris:chanthier villars, pp.450-495. 2. Weber, C.,1931, ”Zum Zerfall eines Flussigkeitsstrahles (On the Disruption of Liquid Jets)”, Zangew, Math. Mechanics, Vol. 11, pp.136. 3. Fromn, J. E, 1984, ”Numerical Calculation of the Fluid Dynamics of Drop-on-Demand Jets”, IBM J. Res. Develop, Vol. 28, NO.3, May. 4. Adams, R. L., and Roy J., 1986, ”A One-Dimensional Numerical Model of a Drop-on-Demand Ink Jet”, Journal of Applied Mechanics,Vol..53/193,March. 5. Lasheras, J.C., Villermaux, E., J. Hopfinger E.,1998, ”Break-up and Atomization of a Round Water Jet by a High-speed Annular Air Jet”, Journal of Fluid Mechanics ,Vol.357, pp. 351-379. 6.Stone, H..A., and Leal, L. G.,1990, ”The Effects of Surfactants on drop deformation and breakup”, Journal of Fluid Mechanics, Vol. 220, pp.161-186. 7. Tjahjadi, M., Stone, H. A. and Ottino, J. M. 1992, ”Satellite and Subsatellite Formation in Capillary Breakup”, Journal of Fluid Mechanics, Vol. 243, pp297-317. 8. Karpp, R.R. and Simon,J.,1893,”An Estimate of the Strength of a Copper Shaped Charge Jet and the Effect of Strength on the Breakup of a Stretching Jet”, US Army Ballistic Research Labs. ,BRL Report NO.. 9. Eggers, J. and Dupont, T.F., 1994, ”Drop Formation in a One-Dimensional Approximation of the Navier-Stokes equation”, Journal of Fluid Mechanics, Vol. 53, pp. 262,205. 10. 張枝成,陳振華,王韋鈞,2004年,”高黏度流體噴射列印行為知實驗研究”,中國機械工程學會第二十一屆全國學術研討會論文集。 11. Cheng S. and Chandra S., 2003, ”A Pneumatic Droplet-On-Demand Generator”, Springer-Verlag 12. Wu, Lin and Hwang ,2005, ”A Numerical Study of the Effect of Operating Parameters on Drop Formation in a Squeeze Mode Inkjet device”, Modelling and Simulation in Materials Science and Engineering, modeling Simulation. Material Science Engineering, Vol. 13, pp. 17-13. 13. Richard J.R., Beris, A.N., and Lenhoff, A.M., 1993, ”Steady Laminar Flow of Liquid-Liquid Jets at High Reynolds Numbers”, Physics.of Fluids, Vol. 5, pp,1703. 14. 宋詠程, 2003,”液滴掉落現象之數值模擬”,中原大學土木工程系碩士學位論文。 15. 邱友良, 2002,”液體噴流斷裂與霧化之機制”,國立台灣海洋大學機械與輪機工程學系碩士學位論文。
摘要: 
本研究是以數值模擬的方式來探討低速液滴形成之過程。以體積流率法(VOF)以及連續表面張力(CSF)的模式,來分析這類二相流的問題。
結果如下:
1.在相同的噴嘴出口速度下,我們改變噴液體出的時間,這意味著
在改變流量的情形下,對液滴的最大影響的就是改變主液滴尺寸大小。
2.液體自噴嘴噴出後到在管壁上形成半球狀的時間可定義為一特徵時間。當液滴即將脫離噴嘴時之軸向速度達到最低值,此後軸向速度繼續升高,直到液滴不在前後變形時達到最大值。最後,行進中的液滴受到唯一的形狀阻力,致軸向速度逐漸下降。在此時間若繼續增加流量,會造成液滴不穩定,且會以衛星液滴產生的危險。若在此時間之前減少流量即可以控制主液滴大小以及衛星滴之形狀。
3.液滴的軸向速度開始略高於出口速度,逐漸形成半球狀,此時液滴的軸向速度成單調遞減。
4.相同的噴嘴出口速度下,增加一個回流,其功用如可以有效回收殘留在噴嘴出口的液體,減少生成衛星液滴的可能,避免避免使得液滴尺寸太大之變化,並避免後續噴出時,殘留的液體可能造成流量增加影響,在相同的回流控制下,凡是液體在噴口回流控制對於衛星液滴產生抑制效果不彰,形成半球之後的特性時間之後還繼續噴出的話,但若在特徵時間之內停止提供流量的話,回流控制對於主液滴尺寸具有決定性之影響;同時,對抑制衛星液滴形成之效果相當明顯。

The present study is to investigate the dynamic characteristics of the micro droplet issuing at low speed from nozzle by numerical simulation. The volume of fraction (VOF) and continuous surface force (CSF) models are employed in the present study. Some important findings are summarized as follows:
1.For the same ejection velocity, change the duration of ejection implies change of liquid volume injected. This change will result in size variation of the main droplet.
2.There exists a characteristic time scale at which the fronts of liquid meniscus forms a hemisphere shape right at the nozzle exist. For injection durations longer than this time scale, excessive volume of droplet will be delivered, leading to possible formation of satellite droplet during break-up. However, if ejection duration is shorter than this time scale, the size of the main droplet can be well controlled and the possibility of satellite droplet will be reduced.
3.The advancing velocity of the ejected liquid first shows a slightly increase above the ejection velocity. It follows a monotonous and steep decrease and reaches a minimum magnitude before it breaks up into droplet .The droplet's advancing speed then increases as a result of the pressure difference across the droplet. It reaches a maximum magnitude near the instant of no streamwise deformation. Finally, the advancing speed decreases again because of the presence of form drag on the moving droplet.
4.The controllability of droplet size and reducing possible satellite droplet formation can be made effective by reducing the ejection duration and applying a suitable magnitude of withdrawing velocity.
URI: http://hdl.handle.net/11455/1769
其他識別: U0005-3108200620090900
Appears in Collections:機械工程學系所

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