The contact line pinning mechanisms of a non-wetting droplet penetrating a permeable substrate are theoretically explained by considering the force balance of volumetric force, capillary force, and pinning and depinning forces. We propose two dimensionless numbers, Bo∗—the ratio of the volumetric force to the capillary force, and Ct—the ratio of the depinning force to the pinning force, to establish a phase diagram that quickly determines the droplet penetration patterns. For Bo∗ ⩽ 1, the droplet will not penetrate the substrate; for Bo∗ > 1 and Ct ⩽ 1, the droplet will penetrate with a pinned contact line; for Bo∗ > 1 and Ct > 1, the droplet will penetrate with contact line shrinking. Contact angle dynamics during contact line pinning and shrinking are further clarified. The time evolutions of the contact area diameter Dc, the droplet height h, the penetrated droplet volume percentage Sp, and the apparent contact angle θ are derived. We further perform a series of lattice Boltzmann simulations, and the results match well with our theoretical analysis. These theoretical and numerical results pave the way to achieve better performances of many important applications that involve droplet penetration.
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June 2023
Research Article|
June 05 2023
The pinning dynamics of a non-wetting droplet penetrating a permeable substrate
Special Collection:
Paint and Coating Physics
Song Hongqing (宋洪庆)
;
Song Hongqing (宋洪庆)
(Formal analysis, Funding acquisition, Investigation, Resources, Supervision)
1
School of Civil and Resource Engineering, University of Science and Technology
Beijing, Beijing 100083, People's Republic of China
2
Joint Lab of Deep Space Exploration Resource Identification
, Beijing, People's Republic of China
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Lao Junming (劳浚铭)
;
Lao Junming (劳浚铭)
(Formal analysis, Methodology, Software, Writing – original draft)
1
School of Civil and Resource Engineering, University of Science and Technology
Beijing, Beijing 100083, People's Republic of China
3
XinoTech Inc., Somerville, Massachusetts 02143, USA and Qingdao
Shandong 266500, China
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Yang Hongen (杨洪恩)
;
Yang Hongen (杨洪恩)
(Formal analysis, Investigation)
1
School of Civil and Resource Engineering, University of Science and Technology
Beijing, Beijing 100083, People's Republic of China
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Pan Bin (潘滨);
Pan Bin (潘滨)
(Conceptualization, Validation)
1
School of Civil and Resource Engineering, University of Science and Technology
Beijing, Beijing 100083, People's Republic of China
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Liu Lin (刘林)
;
Liu Lin (刘林)
(Methodology, Validation)
4
School of Mathematics and Physics, University of Science and Technology
Beijing, Beijing 100083, People's Republic of China
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Xie Chiyu (谢驰宇)
Xie Chiyu (谢驰宇)
a)
(Conceptualization, Investigation, Methodology, Software, Supervision, Validation, Writing – review & editing)
1
School of Civil and Resource Engineering, University of Science and Technology
Beijing, Beijing 100083, People's Republic of China
a)Author to whom correspondence should be addressed: chiyuxie@ustb.edu.cn
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a)Author to whom correspondence should be addressed: chiyuxie@ustb.edu.cn
Note: This paper is part of the special topic, Paint and Coating Physics.
Physics of Fluids 35, 062107 (2023)
Article history
Received:
April 17 2023
Accepted:
May 18 2023
Citation
Hongqing Song, Junming Lao, Hongen Yang, Bin Pan, Lin Liu, Chiyu Xie; The pinning dynamics of a non-wetting droplet penetrating a permeable substrate. Physics of Fluids 1 June 2023; 35 (6): 062107. https://doi.org/10.1063/5.0155070
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