| 摘要: | 本研究進行不同撞擊角度、韋伯數之液滴撞擊試驗，並結合高速攝影機擷取俯視與側視影像，以探討液滴撞擊的幾何特性與運動條件的關係。實驗所得影像使用PCC3.7高速攝影機專用軟體擷取液滴撞擊影像、利用Rapid Resizer圖片範本生成器進行圖像處理，採用邊緣檢測將圖像轉換為線條圖和閾值分割強調圖像細節及MATLAB內建計算與繪製程式，分析液滴撞擊擴展的歷程、形狀、短長徑比等關係。研究結果顯示，正癸烷液滴在不同平板撞擊時，韋伯數對短長徑比影響不大，慣性對形狀變化不顯著。然而水液滴在不同平板上，低韋伯數和不同撞擊角度下，短長徑比與sinϕ值不一致，表明表面張力和接觸角對形狀有顯著影響。不同韋伯數和平衡接觸角下，液滴擴展面積受表面張力和表面能限制，特別是在低撞擊角度和高/低韋伯數情況下，擴展面積小於90°撞擊角度。並利用前人的模型進行最大擴展因數實驗驗證。此外，研究發現水液滴在鐵氟龍平板上的動態行為受We和 ϕ的顯著影響，並會出現非單調的縮回分裂轉變現象。隨著We和 ϕ的變化，液滴在擴展和回縮過程中會表現出不同的模式，包括擴展形成液指、滑動、液膜邊緣的不穩定性、液指分裂成小液滴以及縮回。;This study conducted impact experiments with different impact angles and Weber numbers on droplets, combining high-speed cameras to capture both top-down and side-view images to explore the relationship between the geometric characteristics and motion conditions of droplet impacts. The images obtained from the experiments were analyzed using image processing, website reading, and MATLAB′s built-in computation and plotting programs to investigate the expansion process and the relationships between the shape, aspect ratio, and other factors of the droplet impact. The results indicate that for decane droplets impacting various flat surfaces, the Weber number has little effect on the aspect ratio, and inertia has no significant impact on shape change. However, for water droplets on different plates, at low Weber numbers and different impact angles, the aspect ratio and sinϕ values are inconsistent, indicating that surface tension and contact angle have a significant impact on the shape. Under different Weber numbers and equilibrium contact angles, the droplet expansion area is constrained by surface tension and surface energy, especially at low impact angles and high/low Weber numbers, where the expansion area is less than 90° impact angles. The study also validated the maximum spreading factor using previous models. Additionally, the study finds that the dynamic behavior of water droplets on Teflon plates is significantly influenced by We and ϕ, exhibiting receding breakup non-monotonic transition. As We and ϕvary, droplets display different patterns during expansion and receding, including the formation of liquid fingers, sliding, edge instabilities of the liquid film, breakup liquid fingers into smaller droplets, and receding. |
