| 摘要: | 基質上固著液滴的蒸發在自然和工業應用中普遍存在。這種現象涵蓋了多個物理 方面的複雜相互作用，例如流體動力學、相變、接觸線動力學和化學反應。在工業應 用中，實現均勻沉積模式需要減輕咖啡環效應，這涉及控制眾所周知的毛細流和馬蘭 戈尼流。蒸發引起的各種流動之間的競爭產生不同的固體顆粒沉積模式。在加熱液滴
的情況下，由於材料熱特性對溫度的依賴性，溫度效應會導致複雜的情況。其他因素， 例如自然對流，可能會對乾燥結果產生顯著影響。了解蒸發過程中膠體固著液滴內部 和外部的瞬態流動對於預測最終顆粒沉積模式至關重要，特別是在噴墨列印等應用中。 儘管對純水或揮發性液滴等通用液滴的數值模擬已被廣泛研究，但多組分液滴的綜合 模型仍存在差距，特別是考慮溫度影響的模型。 本研究旨在透過使用任意拉格朗-歐拉 (Arbitrary Lagranian-Eulerian, ALE)框架創建瞬態模型來模擬基質和液滴溫度對固定住的 親水膠體固著液滴的影響，從而解決這一差距。 我們探討了不同液滴和基質溫度對含 顆粒液滴瞬態流場的影響。結果表明，加熱液滴的瞬態流動模式的持續時間延長至未 加熱液滴的近兩倍，而加熱的基材則縮短了該持續時間。加熱的液滴和基底都可以減 輕咖啡環效應，從而產生更均勻的圖案，其順序是加熱的液滴、加熱的基底、然後是未加熱的液滴。這項發現可能為預測最終固體沉積的形成提供有價值的參考意義。未 來的研究方向可能包括探索其他參數，例如粒徑和界面活性劑濃度，以進一步完善模型並增強實驗數據的預測能力。;The evaporation of sessile droplets on a substrate is ubiquitous in natural and industrial applications. This phenomenon encompasses a complex interplay of multiple physics aspects, such as fluid dynamics, phase changes, contact line dynamics, and chemical reactions. In industrial applications, achieving a homogeneous deposition pattern requires mitigating the coffee-ring effect, which involves controlling the well-known capillary and Marangoni flows.
The competition between various flows induced by evaporation produces different solid particle deposition patterns. In the case of a heated droplet, the temperature effect leads to a complicated scenario due to the dependence of material thermal properties on temperature. Other factors, such as natural convection, may significantly contribute to the drying result. Understanding the transient flows inside and outside colloidal sessile droplets during evaporation is crucial for predicting the ultimate particle deposition pattern, particularly in applications such as inkjet printing. Although numerical simulations for generic droplets, such as pure water or volatile droplets, have been extensively studied, there remains a gap in comprehensive models for multicomponent droplets, especially those considering temperature effects. The present study aims
to address this gap by creating a transient model to simulate the substrate and droplet temperature effects on the pinned hydrophilic colloidal sessile droplets using an Arbitrary Lagranian-Eulerian framework. We probe the influence of different droplet and substrate temperatures on the transient flow field in a particle-containing droplet. The results indicate that the duration of the transient flow pattern of a heated droplet is extended to nearly twice that
of a non-heated droplet, while a heated substrate diminishes this duration. Both heated droplets and substrates may mitigate the coffee-ring effect, resulting in a more uniform pattern, with the order of heated drops, heated substrate, and then non-heated droplet. The finding may offer valuable reference implications for predicting the final solid deposition formation. Future research directions include exploring additional parameters such as particle size and surfactant concentration to refine the model further and enhance predictive capabilities with experimental data. |
