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Gao SR, Jia QH, Liu Z, Shi SH, Wang YF, Zheng SF, Yang YR, Hsu SH, Yan WM, Wang XD. Bouncing Dynamics of Drops' Successive Off-Center Impact. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2024; 40:10759-10768. [PMID: 38712734 DOI: 10.1021/acs.langmuir.4c00913] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2024]
Abstract
Bouncing dynamics of a trailing drop off-center impacting a leading drop with varying time intervals and Weber numbers are investigated experimentally. Whether the trailing drop impacts during the spreading or receding process of the leading drop is determined by the time interval. For a short time interval of 0.15 ≤ Δt* ≤ 0.66, the trailing drop impacts during the spreading of the leading drop, and the drops completely coalesce and rebound; for a large time interval of 0.66 < Δt* ≤ 2.21, the trailing drop impacts during the receding process, and the drops partially coalesce and rebound. Whether the trailing drop directly impacts the surface or the liquid film of the leading drop is determined by the Weber number. The trailing drop impacts the surface directly at moderate Weber numbers of 16.22 ≤ We ≤ 45.42, while it impacts the liquid film at large Weber numbers of 45.42 < We ≤ 64.88. Intriguingly, when the trailing drop impacts the surface directly or the receding liquid film, the contact time increases linearly with the time interval but independent of the Weber number; when the trailing drop impacts the spreading liquid film, the contact time suddenly increases, showing that the force of the liquid film of the leading drop inhibits the receding of the trailing drop. Finally, a theoretical model of the contact time for the drops is established, which is suitable for different impact scenarios of the successive off-center impact. This study provides a quantitative relationship to calculate the contact time of drops successively impacting a superhydrophobic surface, facilitating the design of anti-icing surfaces.
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Affiliation(s)
- Shu-Rong Gao
- Research Center of Engineering Thermophysics, North China Electric Power University, Beijing 102206, China
- State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources, North China Electric Power University, Beijing 102206, China
- Key Laboratory of Icing and Anti/De-icing, China Aerodynamics Research and Development Center, Mianyang, Sichuan 621000, China
| | - Qi-Hui Jia
- Research Center of Engineering Thermophysics, North China Electric Power University, Beijing 102206, China
- State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources, North China Electric Power University, Beijing 102206, China
| | - Zhe Liu
- Research Center of Engineering Thermophysics, North China Electric Power University, Beijing 102206, China
- State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources, North China Electric Power University, Beijing 102206, China
| | - Shi-Hua Shi
- Research Center of Engineering Thermophysics, North China Electric Power University, Beijing 102206, China
- State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources, North China Electric Power University, Beijing 102206, China
| | - Yi-Feng Wang
- Research Center of Engineering Thermophysics, North China Electric Power University, Beijing 102206, China
- State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources, North China Electric Power University, Beijing 102206, China
| | - Shao-Fei Zheng
- Research Center of Engineering Thermophysics, North China Electric Power University, Beijing 102206, China
- State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources, North China Electric Power University, Beijing 102206, China
| | - Yan-Ru Yang
- Research Center of Engineering Thermophysics, North China Electric Power University, Beijing 102206, China
- State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources, North China Electric Power University, Beijing 102206, China
| | - Shu-Han Hsu
- Department of Mechanical Engineering, National Taipei University of Technology, Taipei 10608, Taiwan
| | - Wei-Mon Yan
- Department of Mechanical Engineering, National Taipei University of Technology, Taipei 10608, Taiwan
| | - Xiao-Dong Wang
- Research Center of Engineering Thermophysics, North China Electric Power University, Beijing 102206, China
- State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources, North China Electric Power University, Beijing 102206, China
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Jaiswal AK, Khandekar S. Role of offset during drop-on-drop impact dynamics on a superhydrophobic substrate. RESULTS IN SURFACES AND INTERFACES 2023. [DOI: 10.1016/j.rsurfi.2023.100102] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/19/2023]
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Wang Y, Zhao Y, Sun L, Mehrizi AA, Lin S, Guo J, Chen L. Successive Rebounds of Impinging Water Droplets on Superhydrophobic Surfaces. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:3860-3867. [PMID: 35293214 DOI: 10.1021/acs.langmuir.2c00114] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
When a water droplet strikes a superhydrophobic surface, there may be several to a few tens of rebounds before it comes to rest. Although this intriguing multiphase flow phenomenon has received a great deal of attention from interfacial scientists and engineers, the underlying dynamics have not yet been completely resolved. In this paper, we report on an experimental investigation into the bouncing behavior of water droplets impinging on macroscopically flat superhydrophobic surfaces. We show that the restitution coefficient, which quantifies the energy consumed during impact and rebound, exhibits a nonmonotonic dependence on the Weber number. It is the droplet-surface friction that restricts the rebound height of the impinging droplet, so its restitution coefficient increases with the Weber number when the impact velocity is below a critical value. Above this value, the viscous friction within a thin liquid layer close to the superhydrophobic surface becomes dominant, and thus, the restitution coefficient decreases sharply. On the basis of energy analyses, semiempirical formulas are proposed to describe the restitution coefficient, and these can be employed to predict the number of successive rebounds of impinging droplets on superhydrophobic surfaces.
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Affiliation(s)
- Yile Wang
- School of Physics, University of Electronic Science and Technology of China, Chengdu 611731, People's Republic of China
| | - Yage Zhao
- School of Physics, University of Electronic Science and Technology of China, Chengdu 611731, People's Republic of China
| | - Lijie Sun
- School of Physics, University of Electronic Science and Technology of China, Chengdu 611731, People's Republic of China
| | - Abbasali Abouei Mehrizi
- School of Physics, University of Electronic Science and Technology of China, Chengdu 611731, People's Republic of China
| | - Shiji Lin
- School of Physics, University of Electronic Science and Technology of China, Chengdu 611731, People's Republic of China
- Yangtze Delta Region Institute (Huzhou), University of Electronic Science and Technology of China, Huzhou 313001, People's Republic of China
| | - Jianwei Guo
- School of Mechanics and Aerospace Engineering, Southwest Jiaotong University, Chengdu 610031, People's Republic of China
| | - Longquan Chen
- School of Physics, University of Electronic Science and Technology of China, Chengdu 611731, People's Republic of China
- Yangtze Delta Region Institute (Huzhou), University of Electronic Science and Technology of China, Huzhou 313001, People's Republic of China
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