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Liu X, Liu L, Li R, Xie J, Chen Y. Molecular Dynamics Simulation of Dual Nanodroplet Impacts on a Cylindrical Surface. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2024; 40:12828-12841. [PMID: 38853358 DOI: 10.1021/acs.langmuir.4c01655] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2024]
Abstract
Droplet impact behavior is ubiquitous in various fields. However, the dynamics and spreading mechanisms of micro- and nanoscale droplet impact on curved surfaces, particularly in the case of multiple droplets, have yet to be fully elucidated. In this study, molecular dynamics (MD) methods are employed to investigate the dynamic evolution of double nanodroplet impact on a nano cylindrical wall. The effects of droplet spacing, initial impact velocity, and wall wettability on droplet impact characteristics are analyzed. The results demonstrate that there are five impact modes of nanoscale double-droplet impacts with nanocylinders: spreading-partial wrapping-splitting-complete detachment (SPSC), spreading-complete wrapping-complete attachment (SCC), spreading-partial wrapping-complete attachment (SPC), spreading-partial wrapping-partial attachment (SPP), and spreading-partial wrapping-fragmentation-partial attachment (SPFP). The droplet spacing has an insignificant effect on the impact modes but affects the droplets' spreading shape in both the axial and radial directions. The initial velocity and wall wettability have significant impacts on the droplet impact modes and liquid film spreading characteristics. As the initial velocity increases, the liquid film's radial and axial spreading distances gradually increase. Under hydrophobic conditions, the spreading of the droplet is dominant in the radial direction, while under hydrophilic conditions, the spreading is dominant in the axial direction. Properly reducing the droplet spacing, increasing the impact velocity, and enhancing the wall hydrophobicity can promote detaching the droplet from the cylindrical wall.
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Affiliation(s)
- Xuanchen Liu
- School of Energy and Environmental Engineering, Hebei University of Technology, Tianjin 300401, China
| | - Liansheng Liu
- School of Energy and Environmental Engineering, Hebei University of Technology, Tianjin 300401, China
- Hebei Key Laboratory of Geothermal Energy Utilization Technology, Renqiu 062550, China
| | - Rongji Li
- School of Energy and Environmental Engineering, Hebei University of Technology, Tianjin 300401, China
| | - Jun Xie
- School of Energy and Environmental Engineering, Hebei University of Technology, Tianjin 300401, China
| | - Yadong Chen
- School of Energy and Environmental Engineering, Hebei University of Technology, Tianjin 300401, China
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Sykes TC, Harbottle D, Khatir Z, Thompson HM, Wilson MCT. Substrate Wettability Influences Internal Jet Formation and Mixing during Droplet Coalescence. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2020; 36:9596-9607. [PMID: 32787133 DOI: 10.1021/acs.langmuir.0c01689] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The internal dynamics during the axisymmetric coalescence of an initially static free droplet and a sessile droplet of the same fluid are studied using both laboratory experiments and numerical simulations. A high-speed camera captured internal flows from the side, visualized by adding a dye to the free droplet. The numerical simulations employ the volume of fluid method, with the Kistler dynamic contact angle model to capture substrate wettability, quantitatively validated against the image-processed experiments. It is shown that an internal jet can be formed when capillary waves reflected from the contact line create a small tip with high curvature on top of the coalesced droplet that propels fluid toward the substrate. Jet formation is found to depend on the substrate wettability, which influences capillary wave reflection; the importance of the advancing contact angle subordinated to that of the receding contact angle. It is systematically shown via regime maps that jet formation is enhanced by increasing the receding contact angle and by decreasing the droplet viscosity. Jets are seen at volume ratios very different from those accepted for free droplets, showing that a substrate with appropriate wettability can improve the efficiency of fluid mixing.
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Affiliation(s)
- Thomas C Sykes
- EPSRC Centre for Doctoral Training in Fluid Dynamics, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - David Harbottle
- School of Chemical and Process Engineering, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - Zinedine Khatir
- School of Engineering and the Built Environment, Birmingham City University, Birmingham B4 7XG, United Kingdom
| | - Harvey M Thompson
- School of Mechanical Engineering, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - Mark C T Wilson
- School of Mechanical Engineering, University of Leeds, Leeds LS2 9JT, United Kingdom
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Abstract
The dynamic behaviors of two droplets successively impacting inclined surfaces are simulated by a three-dimensional pseudopotential lattice Boltzmann model based on multi-relaxation-time. The effect of velocity ratio of two successive droplets on the contact time is investigated and two rebounding regimes are identified depending on whether the coalesced droplet retouches the surface or not. Increasing the velocity ratio leads to a stronger interaction between the two droplets and the phenomenon of coalesced droplet retouching the surface is observed when the velocity ratio exceeds a threshold, resulting in a longer contact time. An outcome map of droplet rebounding is obtained at various velocity ratios and contact angles of surface. It is found that the coalesced droplet cannot rebound from the surface at a larger velocity ratio and a lower contact angle of surface. Furthermore, the effect of the length between impact points on the contact time is exhibited, and a longer length is beneficial to coalesced droplet rebounding.
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Bala N, Pepona M, Karlin I, Kusumaatmaja H, Semprebon C. Wetting boundaries for a ternary high-density-ratio lattice Boltzmann method. Phys Rev E 2019; 100:013308. [PMID: 31499815 DOI: 10.1103/physreve.100.013308] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2019] [Indexed: 11/07/2022]
Abstract
We extend a recently proposed ternary free-energy lattice Boltzmann model with high density contrast [Phys. Rev. Lett. 120, 234501 (2018)PRLTAO0031-900710.1103/PhysRevLett.120.234501] by incorporating wetting boundaries at solid walls. The approaches are based on forcing and geometric schemes, with implementations optimized for ternary (and, more generally, higher-order multicomponent) models. Advantages and disadvantages of each method are addressed by performing both static and dynamic tests, including the capillary filling dynamics of a liquid displacing the gas phase and the self-propelled motion of a train of drops. Furthermore, we measure dynamic angles and show that the slip length critically depends on the equilibrium value of the contact angles and whether it belongs to liquid-liquid or liquid-gas interfaces. These results validate the model capabilities of simulating complex ternary fluid dynamic problems near solid boundaries, for example, drop impact solid substrates covered by a lubricant layer.
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Affiliation(s)
- Neeru Bala
- Department of Mathematics, Physics and Electrical Engineering, Northumbria University, Newcastle upon Tyne NE1 8ST, United Kingdom
| | - Marianna Pepona
- Department of Physics, Durham University, Durham DH1 3LE, United Kingdom
| | - Ilya Karlin
- Department of Mechanical and Process Engineering, ETH Zurich, CH-8092 Zurich, Switzerland
| | - Halim Kusumaatmaja
- Department of Physics, Durham University, Durham DH1 3LE, United Kingdom
| | - Ciro Semprebon
- Department of Mathematics, Physics and Electrical Engineering, Northumbria University, Newcastle upon Tyne NE1 8ST, United Kingdom
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Sharma KV, Straka R, Tavares FW. Lattice Boltzmann Methods for Industrial Applications. Ind Eng Chem Res 2019. [DOI: 10.1021/acs.iecr.9b02008] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Keerti Vardhan Sharma
- Escola de Química, Federal University of Rio de Janeiro, CEP: 21949-900, Rio de Janeiro, Brazil
- PEQ/COPPE, Federal University of Rio de Janeiro, CEP: 24210-240, Rio de Janeiro, Brazil
| | - Robert Straka
- Department of Heat Engineering and Environment Protection, Faculty of Metals Engineering and Industrial Computer Science, AGH University of Science and Technology, Al. Mickiewicza 30, 30-059, Krakow, Poland
| | - Frederico Wanderley Tavares
- Escola de Química, Federal University of Rio de Janeiro, CEP: 21949-900, Rio de Janeiro, Brazil
- PEQ/COPPE, Federal University of Rio de Janeiro, CEP: 24210-240, Rio de Janeiro, Brazil
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Raman KA. Normal and oblique droplet impingement dynamics on moving dry walls. Phys Rev E 2019; 99:053108. [PMID: 31212429 DOI: 10.1103/physreve.99.053108] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2018] [Indexed: 11/07/2022]
Abstract
Industrial applications that depend on jetting-based technology, such as painting or additive layered manufacturing, involve sequential deposition of droplets onto a moving surface. Spreading and receding dynamics of these impinging drops depend on the momentum transferred by the moving wall to the droplet liquid, which in turn governs the geometric precision and surface finish of the printed outcome. In this work, the impingement dynamics of microdroplets on a flat, smooth, and moving solid surface is computed using a phase-field-based lattice Boltzmann method. Moreover, the motion of the three-phase moving contact line is captured using a geometry-based contact angle formulation. First, we investigate the influence of various process and materials parameters such as wall velocity, droplet viscosity, surface tension, and wettability on the impact behavior of drops. The surface wettability significantly affects the droplet morphology; an elongated tail like structure forms on the rear end of the droplet which becomes sharper as the moving surface becomes more hydrophobic. Furthermore, we examine the underlying flow physics of the symmetry breaking during the spreading and recoiling phases. For a given contact angle, an increase in wall velocity is found to expedite droplet spreading. In addition, for the first time we explore the oblique droplet impingement dynamics on moving dry walls in this work. It is observed that wall momentum affects the structure of the leading edge during the inline impact situations, whereas the moving surface controls the delay in flow reversal inside the droplet for opposing impact scenarios.
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Affiliation(s)
- K Ashoke Raman
- Department of Mechanical Engineering, National University Singapore, 10 Kent Ridge Crescent, Singapore 117576, Singapore
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Li Y, Zheng Y, Chen Y, Lan Z, Ma X. The exact regulation of temperature evolutions for droplet impact on ultrathin cold films at superhydrophilic surface. Chem Eng Sci 2019. [DOI: 10.1016/j.ces.2018.09.014] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Dynamics of simultaneously impinging drops on a dry surface: Role of inhomogeneous wettability and impact shape. J Colloid Interface Sci 2018; 516:232-247. [DOI: 10.1016/j.jcis.2018.01.063] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2017] [Revised: 01/16/2018] [Accepted: 01/17/2018] [Indexed: 11/23/2022]
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Huang J, Yuan Z, Gao S, Liao J, Eslamian M. Understanding Spray Coating Process: Visual Observation of Impingement of Multiple Droplets on a Substrate. ACTA ACUST UNITED AC 2018. [DOI: 10.1007/s12204-018-1914-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Zhang L, Zhu Y, Cheng X. Numerical investigation of multi-droplets deposited lines morphology with a multiple-relaxation-time lattice Boltzmann model. Chem Eng Sci 2017. [DOI: 10.1016/j.ces.2017.06.014] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Ashoke Raman K, Jaiman RK, Lee TS, Low HT. Dynamics of simultaneously impinging drops on a dry surface: Role of impact velocity and air inertia. J Colloid Interface Sci 2017; 486:265-276. [PMID: 27721075 DOI: 10.1016/j.jcis.2016.09.062] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2016] [Revised: 09/24/2016] [Accepted: 09/26/2016] [Indexed: 10/20/2022]
Abstract
Three dimensional simulations are performed to investigate the interaction dynamics between two drops impinging simultaneously on a dry surface. Of particular interest in this study is to understand the effects of impact velocity and surrounding gas density on droplet interactions. To simulate the droplet dynamics and morphologies, a computational framework based on the phase-field lattice Boltzmann formulation is employed for the two-phase flow computations involving high density ratio. Two different coalescence modes are identified when the impinging droplets have different impact speeds. When one of the droplet has a tangential impact velocity component, asymmetric ridge formation is observed. Influence of droplet impact angle on the interaction dynamics of the central ridge is further investigated. Traces of different fluid particles are seeded to analyse internal flow dynamics in oblique impact scenarios. Greater overlapping between the fluid particles is observed with increase in the impact angle. Finally, the present simulations indicate that the ambient gas density has a significant influence to determine the final outcome of the droplet interactions.
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Affiliation(s)
- K Ashoke Raman
- Department of Mechanical Engineering, National University Singapore, 10 Kent Ridge Crescent, Singapore 117576, Singapore.
| | - Rajeev K Jaiman
- Department of Mechanical Engineering, National University Singapore, 10 Kent Ridge Crescent, Singapore 117576, Singapore.
| | - Thong-See Lee
- Department of Mechanical Engineering, National University Singapore, 10 Kent Ridge Crescent, Singapore 117576, Singapore.
| | - Hong-Tong Low
- Department of Mechanical Engineering, National University Singapore, 10 Kent Ridge Crescent, Singapore 117576, Singapore.
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Raman KA, Jaiman RK, Sui Y, Lee TS, Low HT. Rebound suppression of a droplet impacting on an oscillating horizontal surface. Phys Rev E 2016; 94:023108. [PMID: 27627393 DOI: 10.1103/physreve.94.023108] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2016] [Indexed: 06/06/2023]
Abstract
The behavior of a droplet impinging onto a solid substrate can be influenced significantly by the horizontal motion of the substrate. The coupled interactions between the moving wall and the impacting droplet may result in various outcomes, which may be different from the usual normal droplet impact on a stationary wall. In this paper, we present a method to suppress drop rebound on hydrophobic surfaces via transverse wall oscillations, normal to the impact direction. The numerical investigation shows that the suppression of droplet rebound has a direct relationship with the oscillation phase, amplitude, and frequency. For a particular range of oscillation frequencies and amplitudes, a lateral shifting of the droplet position is observed along the oscillating direction. While large oscillation amplitude favors the process of droplet deposition, a high frequency promotes droplet rebound from the oscillating wall. A linear trend in the transition region between deposition and rebound is observed from a scaled phase diagram of the oscillation amplitude versus frequency. We provide a systematic investigation of drop deposition and elucidate the mechanism of rebound suppression through the temporal evolution of the nonaxial kinetic energy and the velocity flow field.
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Affiliation(s)
- K Ashoke Raman
- Department of Mechanical Engineering, National University Singapore, 10 Kent Ridge Crescent, Singapore 117576, Singapore
| | - Rajeev K Jaiman
- Department of Mechanical Engineering, National University Singapore, 10 Kent Ridge Crescent, Singapore 117576, Singapore
| | - Yi Sui
- School of Engineering and Materials Science, Queen Mary University of London, London E1 4NS, United Kingdom
| | - Thong-See Lee
- Department of Mechanical Engineering, National University Singapore, 10 Kent Ridge Crescent, Singapore 117576, Singapore
| | - Hong-Tong Low
- Department of Mechanical Engineering, National University Singapore, 10 Kent Ridge Crescent, Singapore 117576, Singapore
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