- 學位論文
液滴撞擊深液產生彈跳與渦環之研究
Investigation on the Partial Coalescence and Vortex Ring Phenomena of Drop Impact onto Deep Liquid
摘要
本研究探討液滴撞擊深液之彈跳以及渦環之現象，其主要可分為兩部分。第一部分藉由設計一個真空的腔體並控制腔體內的壓力，以觀察液滴以極小速度撞擊液面之彈跳(partial coalescence)情況。研究結果顯示當氣體壓力減少時，液滴彈跳之周期也隨之減少。由此可推論氣體壓力使得液滴更不易浮動於液面，而阻撓第二顆液滴(secondary droplet)的產生。 本文於第二部分探討液滴撞擊液面時產生渦環之機制。本研究可產生重複性極高的渦環，而此研究於之前文獻中尚未提及。若要產生重複性高之渦環，液體的壓力及噴嘴之設計需要更準確地控制。其他之實驗架設考量，誠如如何避免液面表面張力造成的半月形狀(meniscus)、以及減少液體內的流動現象將在內文中更詳細地做介紹。本文亦分析不同大小的液滴撞擊不同種類的液體之現象。實驗結果顯示，液滴的最大的穿透深度(Lmax)決定於其形狀因子(b1/R)，而最大穿透深度發生於形狀因子為0.9時。
並列摘要
An investigation on phenomena occurs when a drop impact onto deep liquid was done and two major cases were concentrated. In very small impact velocity of drop, partial coalescence phenomenon was investigated inside a controllable vacuum chamber. It was found that the reduced air pressure causes the period of coalescence cascade become shorter. It revealed that the reduced air pressure decreases the ability of drop to float and to pinch-off a secondary droplet. Another investigated case was the vortex ring produced by impacted drop. Extensive study on how to produce highly repeatable vortex ring was first conducted. It was found the hydrostatic and control of the drop nozzle is critical in producing repeatable drop-formed vortex ring. More details of experiment set up for such a system are discussed in this report such as how to reduce the meniscus and how to reduce current in the target liquid. As repeatable results have been achieved, series of experiment with various drop sizes and different liquids were conducted. It has been found that the maximum penetration depth Lmax occurs when impact drop shape near the peak of b1/R. The value of b1/R corresponds to the production of Lmax is around 0.9 peak value of b1/R. This finding was found valid for various drop sizes and various liquid conducted.
參考文獻
延伸閱讀
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