Article
Chemistry, Physical
Run Liu, Fang-Fang Xie, Ling-Feng Huang, Yi-Feng Wang, Shu-Hang Lv, Han-Wu Liu, Yan-Ru Yang, Xiao-Dong Wang
Summary: Classical molecular dynamics simulations were used to investigate the impact behaviors of water nanodroplets on a hydrophobic surface in the presence of an external perpendicular electric field. The results showed that the maximum spreading factor of the nanodroplets was enhanced by the electric field, especially at higher field strengths. An analytical model was developed to predict the maximum spreading factor for nanodroplets subjected to a perpendicular electric field, showing good agreement with the MD simulations in a low Reynolds number range.
COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS
(2021)
Article
Mechanics
Ben-Xi Zhang, Jiang-Hai Xu, Kai-Qi Zhu, Qiang Ma, Yan-Ru Yang, Duu-Jong Lee, Xiao-Dong Wang
Summary: The contact time of oblique nanodroplet impacts on nanopillar-arrayed superhydrophobic surfaces is investigated through molecular dynamics simulations. It is found that the contact time is shorter on nanopillar-arrayed surfaces compared to smooth superhydrophobic surfaces under the same impact angles due to the non-axisymmetry of spreading factors. The non-axisymmetry is more significant at impact angles greater than 35 degrees and when the aspect ratio of nanopillars is increased.
Article
Chemistry, Physical
Aiping Zhang, Kai Cui, Yuanyuan Tian, Tieying Wang, Xin He
Summary: This article investigates the impact behavior of binary nanodroplets on hydrophobic and superhydrophobic surfaces, using molecular dynamics simulations to directly capture and analyze the dynamic evolutions of droplets. It provides insights into the practical applications of droplet impact and contributes to advancements in this field.
JOURNAL OF MOLECULAR LIQUIDS
(2023)
Article
Mechanics
Qiang Ma, Yi-Feng Wang, Yi-Bo Wang, Ben-Xi Zhang, Shao-Fei Zheng, Yan-Ru Yang, Duu-Jong Lee, Xiao-Dong Wang
Summary: The effect of surface wettability on the contact time of nanodroplets impacting solid surfaces is investigated using molecular dynamics simulations. The results show that surface wettability has a significant influence on the contact time and restitution coefficient of the nanodroplets, even for superhydrophobic surfaces. The study also establishes theoretical models for the maximum spreading factor, spreading velocity, and retraction velocity, and proposes scaling laws for the spreading and retraction time.
Article
Chemistry, Physical
Hongru Ren, Fan Yang, Chun Li, Chuang Deng
Summary: Through molecular dynamic simulations, the research found that the collision patterns of binary nanodroplets on rough surfaces are similar to those on smooth surfaces, but with significantly different deformation during the spreading phase. This study also revealed distinguished velocity regimes and scaling laws for the maximum spreading factor and timescale, as well as the impact of viscosity on the spreading dynamics in near-inviscid liquid droplet collisions.
APPLIED SURFACE SCIENCE
(2021)
Article
Chemistry, Physical
Yi-Feng Wang, Yi-Bo Wang, Xin He, Ben-Xi Zhang, Yan-Ru Yang, Xiao-Dong Wang, Duu-Jong Lee
Summary: This study investigates the retraction dynamics of low-viscosity water nanodroplets on different surfaces through molecular dynamics simulations. Two retraction regimes, inertial and capillary regimes, are defined, and the retraction velocities are found to depend on the impact velocity and surface wettability.
JOURNAL OF MOLECULAR LIQUIDS
(2022)
Article
Chemistry, Physical
Shuhang Lv, Zhen Yang, Yuanyuan Duan
Summary: This study investigates the retraction kinetics of impacting nanodroplets on hydrophobic surfaces through molecular dynamics simulations. The results show that the normalized spreading radius of nanodroplets with different Weber numbers cannot collapse into a universal curve, unlike macrodroplets. The retraction rate of nanodroplets increases with Weber number and surface hydrophobicity, and a new theoretical model based on energy conservation is proposed for more accurate prediction of the retraction rate in different conditions.
JOURNAL OF MOLECULAR LIQUIDS
(2021)
Article
Chemistry, Physical
Yi-Bo Wang, Yi-Feng Wang, Yan-Ru Yang, Xiao-Dong Wang, Min Chen
Summary: The study investigates the kinematic time and maximum spreading time for the impact of nanodroplets of different types of fluids on solid surfaces with different wettability. It demonstrates that the capillary regime persists for nanodroplet impact, even at the nanoscale, and proposes a universal scaling law that agrees well with molecular dynamics simulations for various liquids and surface wettability.
JOURNAL OF PHYSICAL CHEMISTRY B
(2021)
Article
Chemistry, Physical
Qiang Ma, Yi-Feng Wang, Yi-Bo Wang, Ben-Xi Zhang, Shao-Fei Zheng, Yan-Ru Yang, Duu-Jong Lee, Xiao-Dong Wang
Summary: The bouncing dynamics of water nanodroplets on superhydrophobic Pt surfaces with nanopillar arrays is comprehensively studied using molecular dynamics simulations. It is found that there are critical values of the solid fraction and pillar height to induce pancake bouncing at the moderate Weber number. A theoretical model is developed to quantitatively proclaim the dependence of nanostructure features and the critical Weber number on pancake bouncing.
APPLIED SURFACE SCIENCE
(2023)
Article
Physics, Fluids & Plasmas
Yi-Bo Wang, Yi-Feng Wang, Xin Wang, Ben-Xi Zhang, Yan-Ru Yang, Duu-Jong Lee, Xiao-Dong Wang, Min Chen
Summary: This study uses molecular dynamics simulations to investigate the splash of water nanodroplets on surfaces with different wettability, finding significant influence of surface wettability on the internal breakup of nanodroplets, which differs from the mechanism of macroscopic droplets splash.
PHYSICAL REVIEW FLUIDS
(2021)
Article
Mechanics
Martin Woerner
Summary: This study focuses on the maximum diameter of a drop impacting on a flat solid surface, assuming axisymmetric spreading without splashing. Two novel concepts are introduced to close the energy balance between the initial state of the drop and its maximum spread. An approximate spherical cap model is proposed for the gas-liquid surface area, and viscosity-induced energy loss is related to the total energy dissipation when the drop comes to rest. The fractional dissipation during maximum spread is modeled as a function of an impact parameter (P) that combines the power laws of capillary and viscous regimes.
INTERNATIONAL JOURNAL OF MULTIPHASE FLOW
(2023)
Article
Mechanics
Shu-Rong Gao, Bo-Jian Wei, Jia-Xin Jin, Jin-Sheng Ye, Yi-Feng Wang, Shao-Fei Zheng, Yan-Ru Yang, Xiao-Dong Wang
Summary: The impact of a droplet on hydrophobic surfaces is studied using lattice Boltzmann method simulations. The spreading and retraction processes of the droplet are investigated for different surface wettability, Weber numbers, and Reynolds numbers. The study finds that the spreading time is independent of the above factors, while the retraction time depends on the surface wettability. The contact time, which is the sum of the spreading time and the retraction time, is mainly related to the retraction process and dependent on the surface wettability. A scaling law for the contact time is established based on simulation research and theoretical modeling. The study demonstrates that the scaling law can accurately predict the contact time for droplets impacting hydrophobic surfaces with moderate Weber numbers.
Article
Chemistry, Physical
Yizhou Liu, Tianbao Wang, Zhenyu Song, Min Chen
Summary: The present study investigates the impact of varied impact velocities, initial diameters, droplet supercoolings, and ice surface temperatures on supercooled droplet impact on flat ice surfaces. It is found that droplet spreading at room temperature can be described by equating inertial force to capillary and viscous forces. A universal scaling on maximum spreading is obtained by interpolating between the laws in the capillary and viscous regimes. During supercooled droplet spreading on ice surfaces, dendritic solidification occurs, forming a moving ice-water interface and leading to new droplet spreading mechanisms. The study also proposes a new dimensionless number, the icing number, to scale the icing effects on a flow field in the viscous regime.
APPLIED SURFACE SCIENCE
(2022)
Article
Mechanics
Qiang Ma, Yi-Feng Wang, Yi-Bo Wang, Shao-Fei Zheng, Yan-Ru Yang, Duu-Jong Lee, Xiao-Dong Wang
Summary: Efficient droplet shedding is important for various applications. This study investigates the bouncing dynamics of two nanodroplets on superhydrophobic surfaces. Three bouncing patterns are identified and analyzed to understand their underlying physics. The ring-bouncing pattern, in particular, offers a significant reduction in contact time and provides a new avenue for efficient droplet shedding.
Article
Chemistry, Multidisciplinary
Rao Li, Pengzhe Zhu, Zhihua Yin, Yimeng Xu
Summary: The impact behavior of nanodroplets on textured surfaces is influenced by texture gap and texture angle, with the texture surface producing anisotropy in the spreading and contraction behavior of the droplets after impact.
Article
Chemistry, Physical
Bing-Bing Wang, Chao Yang, Zhi-Ming Xu, Xiao-Dong Wang, Wei-Mon Yan
Summary: The use of a rod electrode was found to effectively suppress particle aggregation and sedimentation in TiO2-H2O nanofluids. An optimal voltage of 0.5 kV was identified for maximum sedimentation suppression, while surface flaws on the electrode were found to be detrimental. The mechanism of sedimentation inhibition by the electrode was speculated to involve charge transfer via contact electrification.
JOURNAL OF DISPERSION SCIENCE AND TECHNOLOGY
(2023)
Article
Thermodynamics
Shao-Fei Zheng, Zi-Yi Wu, Yi-Ying Gao, Yan-Ru Yang, Bengt Sunden, Xiao-Dong Wang
Summary: This study developed a coupled solver to investigate droplet condensation in a moist air environment. The results show that internal conduction, external diffusion, and internal convection have significant impacts on droplet condensation.
NUMERICAL HEAT TRANSFER PART A-APPLICATIONS
(2023)
Article
Thermodynamics
Xiaodong Xue, Wei Han, Zefeng Wang, Hongguang Jin, Xiaodong Wang
Summary: A solar-coal thermochemical hybrid power generation system based on supercritical water gasification is proposed in this paper, which utilizes concentrated solar energy to provide reaction heat for the gasification process at a low temperature. Through energy and exergy analysis, it is found that the proposed system achieves higher net power generation efficiency and exergy efficiency compared to the reference system. The thermochemical method significantly increases the chemical energy of the syngas produced by approximately 29.70%. The proposed system eliminates the need for an air separation unit and syngas purification unit, providing a promising method for the complementary utilization of solar energy and coal.
APPLIED THERMAL ENGINEERING
(2023)
Article
Thermodynamics
Shao-Yu Wang, Zi-Jie Wang, Dan-Qi Wang, Yan-Ru Yang, Shao-Fei Zheng, Shu-Rong Gao, Xiao-Dong Wang, Duu-Jong Lee
Summary: This study investigates the correlations among wettability, dimple curvature radius, and nucleation characteristics on nanostructured surfaces. The results show that nucleation sites are located in the interior of dimples. Increasing surface hydrophobicity or dimple curvature radius would make nucleation more difficult. The obtained critical sizes of nuclei from molecular dynamics simulations are larger than the results estimated by the classical nucleation theory. Additionally, increasing the dimple number benefits the nucleation probability and condensation performance.
APPLIED THERMAL ENGINEERING
(2023)
Article
Chemistry, Multidisciplinary
Dan -Dan Li, Er-Chao Li, Xiang-Yu Ji, Yan-Ru Yang, Xiao-Dong Wang, Guang Feng
Summary: The performance of supercapacitors with different carbon nanotube (CNT) electrodes in tricationic ionic liquid (TIL) electrolytes was assessed using molecular dynamics simulations. The results showed that the capacitance of the electric double-layer (EDL) in TIL increased with increased CNT curvature, and the capacitance of TIL/CNT systems was higher than that of TIL/graphene systems. Different EDL structures and ion distributions were observed near CNT electrodes in TIL compared to monocationic IL (MIL) electrolytes. The TIL also exhibited higher energy-storage ability at high potentials.
Article
Mechanics
Jia-Xin Jin, Shu-Rong Gao, Bo-Jian Wei, Qi-Hui Jia, Shao-Fei Zheng, Yan-Ru Yang, Xiao-Dong Wang
Summary: When a droplet impacts a superhydrophobic surface with macro-ridges off-center, it can split into two asymmetric fragments that exhibit asymmetric spreading and retraction. The contact time of this impact depends on the volume of the larger fragment, which is determined by the off-center distance. This study investigates the dynamics of off-center impacts at relatively high Weber numbers using lattice Boltzmann method simulations to establish a quantitative relationship between the contact time and the volume of the larger fragment, as well as to understand the mechanism of liquid volume redistribution.
Article
Chemistry, Multidisciplinary
Ling-Zhe Zhang, Xu Chen, Yi-Feng Wang, Yan-Ru Yang, Shao-Fei Zheng, Duu-Jong Lee, Xiao-Dong Wang
Summary: This study investigates the dynamic behavior of an off-centered impacting droplet on a superhydrophobic cylinder. The research shows that the introduction of an off-center distance disrupts the symmetry of the droplet, resulting in tilted movement and a direct dripping mode. The study proposes quantitative models for maximum spreading and contact time, highlighting their significance in droplet impact and related applications.
Article
Chemistry, Multidisciplinary
Yi-Bo Wang, Yi-Feng Wang, Qiang Ma, Yan-Ru Yang, Duu-Jong Lee, Xiao-Dong Wang
Summary: Using molecular dynamics simulations, we studied the hole formation of water nanodroplets impacting hydrophilic to hydrophobic surfaces with different static contact angles and initial surface temperatures. We found that the hole dynamics of nanodroplets are different from millimeter-sized droplets, and the hole formation is influenced by surface temperature and wettability. A criterion is developed to predict the hole formation of nanodroplets based on thermal stability analysis. Additionally, we observed the ring-bouncing of nanodroplets triggered by the nucleated vapor bubble.
Article
Chemistry, Multidisciplinary
Shao-Fei Zheng, Yi-Ying Gao, Li-Tao Yang, Shu-Rong Gao, Yan-Ru Yang, Duu-Jong Lee, Bengt Sunden, Xiao-Dong Wang
Summary: Lubricant-infused porous surfaces can enhance the mobility of droplets and improve the heat transfer in dropwise condensation. The wettability and mobility of droplets on such surfaces are influenced by various factors, including interfacial interactions, surface features, and lubricant thickness. This study combines theoretical analysis and molecular dynamics simulations to investigate droplet wettability and mobility on lubricant-infused porous surfaces. The results suggest that a non-cloaking configuration with a thin lubricant layer is recommended for achieving high droplet mobility.
Article
Mechanics
Yi-Bo Wang, He-Xiang Liu, Ning Lan, Ke-Chuan Yan, Yan-Ru Yang, Xiao-Dong Wang
Summary: In this work, the authors investigate microscale electrohydrodynamic conduction pumps of dielectric liquids and find that the electric force differs from macroscale conduction pumps due to the scale effect. The enhanced ionic diffusion in microscale pumps is identified as the trigger for the scale effect. Existing macroscale theoretical models do not work for microscale pumps due to the inaccurate estimation of heterocharge layer thickness. A new theoretical model is developed by modifying the expression of heterocharge layer thickness.
Article
Chemistry, Multidisciplinary
He-Xiang Liu, Yi-Bo Wang, Shao-Yu Wang, Ke-Chuan Yan, Yan-Ru Yang, Xiao-Dong Wang
Summary: This study investigated the conduction of microscale electrohydrodynamic (EHD) pumps under different working regimes and found that existing theoretical models are not accurate in predicting the electric force of microscale EHD conduction pumps, especially in cases with strong diffusion effects. By revising the expression of heterocharge layer thickness and developing a new theoretical model, the researchers were able to accurately predict the electric force of microscale EHD conduction pumps, even in cases with strong diffusion effects. Additionally, the study showed that microscale EHD conduction pumps are more likely to fall into the saturation regime compared to macroscale EHD conduction pumps, and a new dimensionless number, C (0) (D), was proposed to distinguish the working regimes of microscale EHD conduction pumps.
Article
Thermodynamics
Shao-Fei Zheng, We-Kai Liana, Jia-Xing Meng, He-Chen Wang, Shu-Rong Gao, Yan-Ru Yang, Hai-Wang Li, Bengt Sunden, Xiao-Dong Wang
Summary: This study focuses on optimizing the rib arrangements in cooling passages of a turbine blade cooling unit to improve heat transfer performance. The multi-parameter optimization algorithm is applied to find the optimal designs with different performance indices as objective functions. The results show that using the overall performance factor as the objective function can achieve significant reduction in friction loss with moderate heat transfer loss.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2024)
Article
Chemistry, Physical
Yulin Wang, Han Wang, Cheng Wang, Wei He, Yulong Zhao, Xiaodong Wang
Summary: This paper investigates the flow characteristics of water droplets on gas diffusion layer (GDL) surfaces with different roughnesses. The results show that the roughness of GDL surfaces has a significant impact on water droplet flow, with lower Polytetrafluoroethylene (PTFE) content leading to increased surface roughness and longer droplet discharge time, spreading area, and deformation. On the other hand, higher PTFE content results in smoother flow and shorter droplet discharge time. Comparatively, water droplet flow on rough GDL surfaces exhibits longer discharge time, larger spreading area, stronger fluctuations, and larger pressure drop compared to smooth GDL surfaces.
JOURNAL OF POWER SOURCES
(2024)
Article
Thermodynamics
Yi-Bo Wang, Ling-Feng Huang, Ning Lan, Shuo-Lin Wang, Ben-Xi Zhang, Yan-Ru Yang, Xiao-Dong Wang, Duu-Jong Lee
Summary: This study numerically investigated the heat transfer process in a wavy channel enhanced by electrohydrodynamics (EHD), and found that the mechanisms of EHD-enhanced heat transfer differ from a straight channel. Based on the simulation results, strategies for aligning multielectrodes in wavy channels were proposed, and design criteria for enhanced heat transfer performance in discontinuous wavy channels with multiple electrodes were provided.
APPLIED THERMAL ENGINEERING
(2024)
Article
Thermodynamics
Lin Lin, Zhen-Hua Jing, Shao-Fei Zheng, Wei-Hsin Chen, Duu-Jong Lee, Xiao-Dong Wang
Summary: In this work, a new carrier transport model for hetero-junction thermoelectric generators is developed, and multiple micro TEG designs are studied to investigate their performance. The results show that both homo-heterojunction and inverse-heterojunction significantly improve the thermoelectric performance, with homo-heterojunction performing better at low working temperatures and inverse-heterojunction performing better at high working temperatures. Finally, a novel heterojunction combining both homo-and inverse-heterojunction is proposed, which further improves the thermoelectric efficiency.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2023)