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    Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/43480

    Title: 液滴撞擊移動表面之研究;Investigation of Liquid Droplet Impacting on a Moving Surface
    Authors: 任天熹;Tain-shi Zen
    Contributors: 機械工程研究所
    Keywords: 飛濺;液滴撞擊;附著;drop impact;splashing;deposition
    Date: 2010-05-18
    Issue Date: 2010-12-08 13:41:59 (UTC+8)
    Publisher: 國立中央大學
    Abstract: 本論文是研究液滴撞擊移動乾表面之撞擊結果。在撞擊初期,液滴底部的液體將附著於移動表面並隨之運動,而液滴的其餘部份則是受到墜落慣性力的控制,停留在撞擊點上方並向四周擴展。實驗中使用高表面張力之液滴—水,而撞擊目標為表面光滑的旋轉矽晶圓。比較水滴撞擊移動面與靜止面之結果,兩者間最顯著的不同為:一是水滴附著在移動面上,使得液膜擴張的形狀被拉長成為不對稱,若移動面的速度愈大,液滴擴張的面積也愈大;反之,水滴撞擊靜止面會獲得對稱的液膜擴張。二是水滴撞擊高速運動之光滑面會發生飛濺(或分離)現象,原因是移動面速度到達一臨界值,水滴的表面張力被克服,使得液體發生分裂而造成飛濺(或分離)現象,移動面速度愈快,分離出去的液體量也愈多,此一狀況在水滴撞擊靜止且光滑之乾表面是不會發生的。 當實驗材料改用低表面張力之液滴—酒精,撞擊光滑的移動面—矽晶圓,且表面有一傾斜角度。研究中改變表面傾斜角度與速度,觀察撞擊結果的變化。當酒精滴撞擊靜止之傾斜面,酒精液膜流動受到重力的作用,向下方擴展的液膜較不穩定,易出現劇烈的飛濺現象,相對的朝上方擴展的液膜則較為穩定。當液滴撞擊移動面時,飛濺易發生在表面移動的反方向。將上述兩個特性結合,使傾斜面向下方移動,將使得原本應該發生之飛濺轉變為附著,也就是使液滴的附著區間增大,傾斜角度愈大則此一現象愈明顯。 This thesis investigates the outcomes of drop impacting onto the moving dry surface. In the early stage of impacting, the bottom of the liquid drop adheres to the surface and is dragged by the moving surface simultaneously. The remainder of the drop governed by the force of inertia will remain and expand above the impacting point. Water drops with the characteristics of high surface tension and a smooth surface of rotating wafer are adopted in the experiment. Two major different outcomes are significantly appeared between the stationary and moving surfaces after impacting. Firstly, the deposited film is elongated by a moving surface to form an asymmetrical geometry, and the area of deposited film enlarges when the surface velocity increases. Secondly, either detachment or splashing which is impossible to be occurred in a smooth and stationary surface appears in high surface velocity. When the surface velocity or impingement angle reaches critical value, the upper portion of the droplet can be overcome the surface tension to result in droplet floating on the air, and then the detachment or splashing is formed. The faster surface velocity can reach the larger amount of detaching liquid is obtained. The ethanol drops have the advantage of low surface tension. The impact outcome of an ethanol drop on a moving inclined surface is also investigated in the experiment. The outcome transformations can be observed by varying the surface inclined angles and the moving velocities. The gravity not only can promote the instability of the expanding film at downward flow also can stabilize the film at upward flow during the drop impact onto a stationary inclined surface. Considering the horizontal moving surface, the surface velocity excites the occurrence of splashing that is toward the opposite direction of surface movement, whereas it suppresses the splashing in the same direction of surface movement. When the inclined surface moves downward at a proper surface velocity, the impact outcomes can be changed from downward splashing to deposition. In other words, the regime of deposition is enlarged by an appropriate surface velocity, and this tendency is more obvious with a larger inclined angle.
    Appears in Collections:[機械工程研究所] 博碩士論文

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