Vaikuntanathan V, Sivakumar D. Maximum Spreading of Liquid Drops Impacting on Groove-Textured Surfaces: Effect of Surface Texture.
LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2016;
32:2399-409. [PMID:
26885767 DOI:
10.1021/acs.langmuir.5b04639]
[Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
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, βm,⊥ is seen to be less than that measured parallel to grooves, βm,∥. The difference between βm,⊥ and βm,∥ increases with drop impact velocity. This deviation of βm,⊥ from βm,∥ 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 βm,⊥ from βm,∥ compared to other possible candidates. A unified model, incorporating all the above-mentioned mechanisms, is formulated, which predicts βm,⊥ 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 βm,∥ with an average error of 6.3%.
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