2005-08-012024-05-17https://scholars.lib.ntu.edu.tw/handle/123456789/695373摘要：液滴與液滴之間或液滴與固體或液體層表面的碰撞現象一直是眾多科學及技術層面的考量，諸如雨滴間的結合或其與地層土壤或海洋表面的撞擊、噴霧技術如噴墨印表機及表面鍍膜或繪圖、液態燃料引擎內的油滴分佈等。本研究計畫之起始動機在於後者，因為油滴散佈的狀況將直接主導燃氣質量、動量、及能量的分布，進而影響引擎的燃燒及推進效能。在碰撞過程中，由於流體動量、表面張力、液面間產生的壓力層等結構改變，運動液滴於碰撞後將發生結合、反彈、結合再分解、或濺散等現象，我們將針對不同的參數條件做有系統的量測，找出相異碰撞現象與主要控制因數的關係，同時應用適當的數值計算方法剖析液滴與固體或液體層面的碰撞動力行為；此外亦針對雙液滴碰撞尚未解析的現象特別發展實驗技術，以擷取其在極高動能撞擊下的結果，並佐以理論與數值分析，期能深入探討流體力學相異界面間的結合現象，亦能直接或間接應用於其他相關領域。<br> Abstract: The collision dynamics between two droplets and between a droplet and a wet/dry surface has played a key role in miscellaneous disciplines such as meteorology, printing/coating technologies, nuclear fusion, and spray combustion in liquid-fueled burning devices. The purpose of this project is to identify some unclear outcomes which have not been explored before when a droplet impinges another droplet and upon a wet or solid surface, in the hope of better understanding the flow dynamics between the interfaces characterizing different phases. It is known that the collision can lead to merging (absorption), bouncing, and splashing in terms of the variations of a dimensionless Weber number, which is the ratio of the impact energy and surface energy, and an impact parameter, which is the angle between the colliding trajectories. However, a systematic investigation for the corresponding parametric conditions of the droplet-surface collision still lags behind that for droplet-droplet collision, particularly for a droplet impacting on a thin film whereby a dimensionless parameter of film thickness is not easily controlled for small droplets. Therefore, we aim to study the diverse transition phenomena and map a global regime diagram for the collision between a droplet and a wet/dry surface, particularly for the boundaries of absorption-splashing and absorption-bouncing transformations, occurring at high and low Weber numbers respectively, which have not been fully identified and comprehended. Meanwhile, for droplet-droplet collision, the regime of extremely high Weber number is another topic of interest. The conventional regime diagram covers at most that of separation associated with a few daughter droplets. According to the impaction theory and comparison with the droplet-surface collision, a fingering structure caused by capillary instability and substantial formation of multiple secondary droplets due to subsequent pinching could exist at relatively high Weber number that has not been investigated.液滴碰撞兩相流界面物理Key word: droplet collisiontwo-phase flowinterface physics