Maximum Spreading of Liquid Drops Impacting on Groove-Textured Surfaces: Effect of Surface Texture

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• 作者：Visakh Vaikuntanathan ; D. Sivakumar
• 刊名：Langmuir
• 出版年：2016
• 出版时间：March 15, 2016
• 年：2016
• 卷：32
• 期：10
• 页码：2399-2409
• 全文大小：622K
• ISSN：1520-5827

文摘

Maximum spreading of liquid drops impacting on solid surfaces textured with unidirectional parallel grooves is studied for drop Weber number in the range 1–100 focusing on the role of texture geometry and wettability. The maximum spread factor of impacting drops measured perpendicular to grooves, β_m,⊥ is seen to be less than that measured parallel to grooves, β_m,∥. The difference between β_m,⊥ and β_m,∥ increases with drop impact velocity. This deviation of β_m,⊥ from β_m,∥ is analyzed by considering the possible mechanisms, corresponding to experimental observations—(1) impregnation of drop into the grooves, (2) convex shape of liquid–vapor interface near contact line at maximum spreading, and (3) contact line pinning of spreading drop at the pillar edges—by incorporating them into an energy conservation-based model. The analysis reveals that contact line pinning offers a physically meaningful justification of the observed deviation of β_m,⊥ from β_m,∥ compared to other possible candidates. A unified model, incorporating all the above-mentioned mechanisms, is formulated, which predicts β_m,⊥ on several groove-textured surfaces made of intrinsically hydrophilic and hydrophobic materials with an average error of 8.3%. The effect of groove-texture geometrical parameters on maximum drop spreading is explained using this unified model. A special case of the unified model, with contact line pinning absent, predicts β_m,∥ with an average error of 6.3%.