Pub Date : 2025-11-24DOI: 10.1016/j.ijmultiphaseflow.2025.105560
Mathis Fricke , Lisanne Gossel , Joël De Coninck
We revisit the classical problem of liquid imbibition in a single tube with spatially varying wettability. Starting from the Lucas–Washburn equation, we derive analytical solutions for the imbibition time (crossing time) in systems where wettability alternates between different materials. For ordered arrangements, we demonstrate that the imbibition speed depends non-trivially on the spatial distribution, with the ”more hydrophobic-first” configuration being optimal. For disordered systems, where segment lengths follow a Gaussian distribution, we show that the classical Cassie–Baxter contact angle, originally derived for static wetting, fails to predict the dynamics of capillary-driven flow. To address this, we propose a new weighted harmonic averaging method for the contact angle, which accurately describes the viscous crossing time in such heterogeneous systems. Our findings reveal fundamental insights into the role of wettability heterogeneity in capillary-driven flow, offering a basis for understanding imbibition dynamics in complex heterogeneous systems.
The research data and the software supporting this study are openly available at DOI:10.5281/zenodo.14537452.
{"title":"Beyond the Cassie–Baxter model: New insights for predicting imbibition in complex systems","authors":"Mathis Fricke , Lisanne Gossel , Joël De Coninck","doi":"10.1016/j.ijmultiphaseflow.2025.105560","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105560","url":null,"abstract":"<div><div>We revisit the classical problem of liquid imbibition in a single tube with spatially varying wettability. Starting from the Lucas–Washburn equation, we derive analytical solutions for the imbibition time (crossing time) in systems where wettability alternates between different materials. For ordered arrangements, we demonstrate that the imbibition speed depends non-trivially on the spatial distribution, with the ”more hydrophobic-first” configuration being optimal. For disordered systems, where segment lengths follow a Gaussian distribution, we show that the classical Cassie–Baxter contact angle, originally derived for static wetting, fails to predict the dynamics of capillary-driven flow. To address this, we propose a new weighted harmonic averaging method for the contact angle, which accurately describes the viscous crossing time in such heterogeneous systems. Our findings reveal fundamental insights into the role of wettability heterogeneity in capillary-driven flow, offering a basis for understanding imbibition dynamics in complex heterogeneous systems.</div><div>The research data and the software supporting this study are openly available at <span><span>DOI:10.5281/zenodo.14537452</span><svg><path></path></svg></span>.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"196 ","pages":"Article 105560"},"PeriodicalIF":3.8,"publicationDate":"2025-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145610442","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-24DOI: 10.1016/j.ijmultiphaseflow.2025.105561
Qingshan Chen , Qinrui Zhang , Cong Wang , Kailun Guo , Mingjun Wang , Xiaoyan Wang , Wenxi Tian , Suizheng Qiu , Guanghui Su
Spray cooling technology, known for its high heat transfer efficiency, is widely applied in high heat flux scenarios. However, existing studies often lack efficient model transition strategies for simulating droplet impingement, liquid film formation, and evaporative heat and mass transfer processes, resulting in high computational costs and limited applicability to large-scale fields. This study proposes an innovative numerical spray cooling method called DPM-VOF-LEE. It integrates Volume of Fluid (VOF) and Discrete Phase Model (DPM) with an evaporative heat transfer model through a transition strategy. The DPM model is employed for efficient droplet tracking in the far-field region. In contrast, the VOF model is applied near the wall to resolve liquid film morphology and heat transfer accurately. This model transition method significantly reduces mesh requirements and improves scalability. It is especially suitable for large-area or multi-nozzle spray cooling systems. Results indicate that vertical single-nozzle spraying exhibits the best cooling performance. In dual-nozzle configurations, interference regions enhance heat transfer. Cooling efficiency increases by more than 78 % compared with non-interference cases. For triple-nozzle configurations, the staggered layout achieves faster average temperature reduction on aluminum plates, with cooling efficiency 8.32 % higher than the inline layout.
{"title":"Numerical study of spray cooling: The effect of nozzle arrangement on heat transfer performance","authors":"Qingshan Chen , Qinrui Zhang , Cong Wang , Kailun Guo , Mingjun Wang , Xiaoyan Wang , Wenxi Tian , Suizheng Qiu , Guanghui Su","doi":"10.1016/j.ijmultiphaseflow.2025.105561","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105561","url":null,"abstract":"<div><div>Spray cooling technology, known for its high heat transfer efficiency, is widely applied in high heat flux scenarios. However, existing studies often lack efficient model transition strategies for simulating droplet impingement, liquid film formation, and evaporative heat and mass transfer processes, resulting in high computational costs and limited applicability to large-scale fields. This study proposes an innovative numerical spray cooling method called DPM-VOF-LEE. It integrates Volume of Fluid (VOF) and Discrete Phase Model (DPM) with an evaporative heat transfer model through a transition strategy. The DPM model is employed for efficient droplet tracking in the far-field region. In contrast, the VOF model is applied near the wall to resolve liquid film morphology and heat transfer accurately. This model transition method significantly reduces mesh requirements and improves scalability. It is especially suitable for large-area or multi-nozzle spray cooling systems. Results indicate that vertical single-nozzle spraying exhibits the best cooling performance. In dual-nozzle configurations, interference regions enhance heat transfer. Cooling efficiency increases by more than 78 % compared with non-interference cases. For triple-nozzle configurations, the staggered layout achieves faster average temperature reduction on aluminum plates, with cooling efficiency 8.32 % higher than the inline layout.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"196 ","pages":"Article 105561"},"PeriodicalIF":3.8,"publicationDate":"2025-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145622980","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-20DOI: 10.1016/j.ijmultiphaseflow.2025.105539
C. Gadal , J. Schneider , C. Bonamy , J. Chauchat , Y. Dossmann , S. Kiesgen de Richter , M.J. Mercier , F. Naaim-Bouvet , M. Rastello , L. Lacaze
This study investigates the early slumping regime of particle-laden gravity currents from full-depth dam-break releases, combining laboratory experiments and two-fluid simulations. By systematically exploring the parameter space, it highlights the influence of the bottom slope, particle volume fraction and particle settling velocity on the flow dynamics.
{"title":"Particle-laden gravity currents: The lock-release slumping regime at the laboratory scale","authors":"C. Gadal , J. Schneider , C. Bonamy , J. Chauchat , Y. Dossmann , S. Kiesgen de Richter , M.J. Mercier , F. Naaim-Bouvet , M. Rastello , L. Lacaze","doi":"10.1016/j.ijmultiphaseflow.2025.105539","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105539","url":null,"abstract":"<div><div>This study investigates the early slumping regime of particle-laden gravity currents from full-depth dam-break releases, combining laboratory experiments and two-fluid simulations. By systematically exploring the parameter space, it highlights the influence of the bottom slope, particle volume fraction and particle settling velocity on the flow dynamics.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"195 ","pages":"Article 105539"},"PeriodicalIF":3.8,"publicationDate":"2025-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145615324","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-19DOI: 10.1016/j.ijmultiphaseflow.2025.105551
S. Abbasi, A. Mehdizadeh
Understanding particle transport and deposition in wall-bounded turbulent flows is critical for numerous industrial and environmental applications. In this study, we investigate the dispersion and deposition dynamics of small aerosol and hydrosol particles in a turbulent channel flow at a friction Reynolds number of using point-particle direct numerical simulations (PP–DNS). By decomposing the particle acceleration into drag, lift, pressure gradient, virtual mass, and Basset history components, we assess the relative influence of each acceleration across a range of particle sizes and density ratios (aerosol and hydrosol) in an upward flow motion, i.e. opposite direction of gravity. Our results show that while drag dominates the particle dynamics particularly for aerosols, lift becomes increasingly important with rising particle size. The Basset history, pressure gradient and virtual mass accelerations have only a negligible contribution to the total acceleration. Regarding hydrosol, pressure gradient has a constant contribution to particle acceleration, largely independent of particle size, where the effect of virtual mass decreases with the increase of particle size. On the other hand, Basset history acceleration, shows size-dependent behavior. For small particles, the Basset history acceleration contributes to the particle acceleration with a magnitude comparable to the pressure gradient. As the particle size increases, this contribution decreases, and its dynamics changes once the hydrosol particle size approaches the Kolmogorov scale. Additionally, both pressure gradient and Basset history have significant input on deposition for hydrosol particles comparable to Kolmogorov length scale.
{"title":"Comparative study of aerosol and hydrosol transport and deposition dynamics in turbulent wall-bounded flows","authors":"S. Abbasi, A. Mehdizadeh","doi":"10.1016/j.ijmultiphaseflow.2025.105551","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105551","url":null,"abstract":"<div><div>Understanding particle transport and deposition in wall-bounded turbulent flows is critical for numerous industrial and environmental applications. In this study, we investigate the dispersion and deposition dynamics of small aerosol and hydrosol particles in a turbulent channel flow at a friction Reynolds number of <span><math><mrow><mi>R</mi><msub><mrow><mi>e</mi></mrow><mrow><mi>τ</mi></mrow></msub><mo>=</mo><mn>180</mn></mrow></math></span> using point-particle direct numerical simulations (PP–DNS). By decomposing the particle acceleration into drag, lift, pressure gradient, virtual mass, and Basset history components, we assess the relative influence of each acceleration across a range of particle sizes and density ratios (aerosol and hydrosol) in an upward flow motion, i.e. opposite direction of gravity. Our results show that while drag dominates the particle dynamics particularly for aerosols, lift becomes increasingly important with rising particle size. The Basset history, pressure gradient and virtual mass accelerations have only a negligible contribution to the total acceleration. Regarding hydrosol, pressure gradient has a constant contribution to particle acceleration, largely independent of particle size, where the effect of virtual mass decreases with the increase of particle size. On the other hand, Basset history acceleration, shows size-dependent behavior. For small particles, the Basset history acceleration contributes to the particle acceleration with a magnitude comparable to the pressure gradient. As the particle size increases, this contribution decreases, and its dynamics changes once the hydrosol particle size approaches the Kolmogorov scale. Additionally, both pressure gradient and Basset history have significant input on deposition for hydrosol particles comparable to Kolmogorov length scale.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"195 ","pages":"Article 105551"},"PeriodicalIF":3.8,"publicationDate":"2025-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145569383","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-19DOI: 10.1016/j.ijmultiphaseflow.2025.105553
Eric R. Upchurch , Yaxin Liu , Evren M. Ozbayoglu
An experimental investigation into Taylor bubble countercurrent behavior in an eccentric 0.1524 m x 0.1016 m (6 in. x 4 in.) annulus using non-Newtonian fluids is presented. This annulus configuration and the fluids tested are commonly used in oil, gas and geothermal drilling operations, but are not reflected in the existing research literature. Fluid rheology, annulus inclination, and internal pipe rotational speed are varied to provide an understanding of Taylor bubble physics under countercurrent flow and its implications for effectively managing unwanted upward gas migration that can occur in a wellbore during drilling operations in fractured or vugular rock formations.
Water and Bingham plastic fluids of ever-increasing plastic viscosity (μp) and yield point (τy) are tested to determine the minimum average downward fluid velocity (i.e., ) that each requires to halt Taylor bubble migration. Increases in μp and τy do not monotonically reduce . Instead, moderate increases up to μp = 31 cP and τy = 40 lb/100 ft2 increase – while further increases in μp and τy reduce , but at the cost of increased friction pressures in the wellbore. Accepting a larger reduces friction pressures but requires using larger fluid volumes during the drilling process. Conversely, minimizing induces higher friction pressure on the wellbore. Determining the appropriate balance of these factors, and others, when planning drilling operations requires integrating the findings of our low-pressure experiments with that of recently published high-pressure Taylor bubble migration experiments. A discussion of the various considerations in such planning is presented.
实验研究了偏心0.1524 m x 0.1016 m (6 in。介绍了使用非牛顿流体的x4英寸)环空。这种环空结构和测试的流体通常用于石油、天然气和地热钻井作业，但在现有的研究文献中没有反映出来。流体流变学、环空倾斜度和管内旋转速度的变化，提供了对逆流作用下泰勒气泡物理特性的理解，以及它对有效管理压裂或空化岩层钻井作业期间井筒中可能出现的有害向上运移的影响。测试了不断增加的塑性粘度（μp）和屈服点（τy）的水和宾厄姆塑性流体，以确定最小的平均向下流体速度（即V - min），每个流体都需要停止泰勒气泡迁移。μp和τy的增加不会单调地减少V的最小值。相反，适度增加到μp = 31 cP和τy = 40 lb/100 ft2会增加V的min，而μp和τy的进一步增加会减少V的min，但代价是增加井筒中的摩擦压力。接受较大的V - min可以减少摩擦压力，但在钻井过程中需要使用较大的流体体积。相反，最小化V - min会在井筒上产生更高的摩擦压力。在规划钻井作业时，需要将我们的低压实验结果与最近发表的高压Taylor气泡迁移实验结果相结合，以确定这些因素以及其他因素的适当平衡。讨论了这种规划中的各种考虑因素。
{"title":"Controlling Taylor bubble migration in a non-concentric annulus: full-scale experiments applied to well drilling operations","authors":"Eric R. Upchurch , Yaxin Liu , Evren M. Ozbayoglu","doi":"10.1016/j.ijmultiphaseflow.2025.105553","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105553","url":null,"abstract":"<div><div>An experimental investigation into Taylor bubble countercurrent behavior in an eccentric 0.1524 m x 0.1016 m (6 in. x 4 in.) annulus using non-Newtonian fluids is presented. This annulus configuration and the fluids tested are commonly used in oil, gas and geothermal drilling operations, but are not reflected in the existing research literature. Fluid rheology, annulus inclination, and internal pipe rotational speed are varied to provide an understanding of Taylor bubble physics under countercurrent flow and its implications for effectively managing unwanted upward gas migration that can occur in a wellbore during drilling operations in fractured or vugular rock formations.</div><div>Water and Bingham plastic fluids of ever-increasing plastic viscosity (<em>μ<sub>p</sub></em>) and yield point (<em>τ<sub>y</sub></em>) are tested to determine the minimum average downward fluid velocity (i.e., <span><math><msub><mover><mrow><mi>V</mi></mrow><mo>‾</mo></mover><mi>min</mi></msub></math></span>) that each requires to halt Taylor bubble migration. Increases in <em>μ<sub>p</sub></em> and <em>τ<sub>y</sub></em> do not monotonically reduce <span><math><msub><mover><mrow><mi>V</mi></mrow><mo>‾</mo></mover><mi>min</mi></msub></math></span>. Instead, moderate increases up to <em>μ<sub>p</sub></em> = 31 cP and <em>τ<sub>y</sub></em> = 40 lb/100 ft<sup>2</sup> increase <span><math><msub><mover><mrow><mi>V</mi></mrow><mo>‾</mo></mover><mi>min</mi></msub></math></span> – while further increases in <em>μ<sub>p</sub></em> and <em>τ<sub>y</sub></em> reduce <span><math><msub><mover><mrow><mi>V</mi></mrow><mo>‾</mo></mover><mi>min</mi></msub></math></span>, but at the cost of increased friction pressures in the wellbore. Accepting a larger <span><math><msub><mover><mrow><mi>V</mi></mrow><mo>‾</mo></mover><mi>min</mi></msub></math></span> reduces friction pressures but requires using larger fluid volumes during the drilling process. Conversely, minimizing <span><math><msub><mover><mrow><mi>V</mi></mrow><mo>‾</mo></mover><mi>min</mi></msub></math></span> induces higher friction pressure on the wellbore. Determining the appropriate balance of these factors, and others, when planning drilling operations requires integrating the findings of our low-pressure experiments with that of recently published high-pressure Taylor bubble migration experiments. A discussion of the various considerations in such planning is presented.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"195 ","pages":"Article 105553"},"PeriodicalIF":3.8,"publicationDate":"2025-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145615311","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This study explores the influence of rectangular cavity wettability and size on explosive boiling through nonequilibrium molecular dynamics (MD) simulations. Hybrid wettability rectangular cavity nanostructured surfaces (HWRN) were constructed. Among them, surfaces HWRN-A1 to HWRN-A6 represent a gradual decrease in cavity wettability, while surfaces HWRN-B1 to HWRN-B6 correspond to a gradual increase in the area ratio of the superhydrophobic cavity surface. The atomic energy distribution of the argon liquid film was analyzed to investigate the mechanism of surface wettability on bubble nucleation. The heated surface temperature increased from 90 K to 180 K in 15 ns (6K/ns). The simulation results indicate that reducing the wettability of the rectangular cavities on the HWRN-A surface shortens the time for both bubble nucleation and explosive boiling. The explosive boiling time of HWRN-A6 (superhydrophobic cavity) is 225 ps earlier than that of HWRN-A1 (superhydrophilic cavity). The bubble nucleation time demonstrates a decreasing then increasing trend with the expansion of HWRN-B's cavity area. Under the conditions of this study, the optimal area ratio of HWRN-B was 8% (B3). The surfaces with the largest CHF in the HWRN-A and HWRN-B groups of studies were HWRN-A6 (5.4 × 10–4eV/(nm2·ps)) and HWRN-B3 (5.7 × 10–4 eV/(nm2·ps)), respectively.
{"title":"Molecular dynamics study of boiling on the surface of hybrid wettability rectangular cavity nanostructures","authors":"Dongling Liu, Xiaoping Luo, Yijie Fan, Jinxin Zhang","doi":"10.1016/j.ijmultiphaseflow.2025.105555","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105555","url":null,"abstract":"<div><div>This study explores the influence of rectangular cavity wettability and size on explosive boiling through nonequilibrium molecular dynamics (MD) simulations. Hybrid wettability rectangular cavity nanostructured surfaces (HWRN) were constructed. Among them, surfaces HWRN-A1 to HWRN-A6 represent a gradual decrease in cavity wettability, while surfaces HWRN-B1 to HWRN-B6 correspond to a gradual increase in the area ratio of the superhydrophobic cavity surface. The atomic energy distribution of the argon liquid film was analyzed to investigate the mechanism of surface wettability on bubble nucleation. The heated surface temperature increased from 90 K to 180 K in 15 ns (6K/ns). The simulation results indicate that reducing the wettability of the rectangular cavities on the HWRN-A surface shortens the time for both bubble nucleation and explosive boiling. The explosive boiling time of HWRN-A6 (superhydrophobic cavity) is 225 ps earlier than that of HWRN-A1 (superhydrophilic cavity). The bubble nucleation time demonstrates a decreasing then increasing trend with the expansion of HWRN-B's cavity area. Under the conditions of this study, the optimal area ratio of HWRN-B was 8% (B3). The surfaces with the largest CHF in the HWRN-A and HWRN-B groups of studies were HWRN-A6 (5.4 × 10<sup>–4</sup>eV/(nm<sup>2</sup>·ps)) and HWRN-B3 (5.7 × 10<sup>–4</sup> eV/(nm<sup>2</sup>·ps)), respectively.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"195 ","pages":"Article 105555"},"PeriodicalIF":3.8,"publicationDate":"2025-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145615310","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-18DOI: 10.1016/j.ijmultiphaseflow.2025.105554
Hanlin Zhou , Ningjing Mao , Yong Liu , Hong Liang , Haihu Liu
Coalescence dynamics of two equal-sized droplets coated with a fixed number of particles is numerically investigated using the lattice Boltzmann color-gradient model coupled with particle dynamics. By varying particle distribution range, we first show that the addition of particles can retard droplet deformation, and even in the absence of particles in the growth region of liquid bridge, more particles distributed at the axial ends of droplets significantly hinder droplet deformation. This is mainly because high kinetic energy region, which is concentrated at the axial ends of the droplet, is inhibited by particles in this region. We then vary the viscosity ratio of ambient fluid to droplet and find that for a moderate viscosity ratio, decreasing the particle distribution range causes the droplet oscillation mode to shift from critically damped to overdamped. In the under-damped mode, droplets are able to reach steady state earlier with a decrease in particle distribution range, while an opposite trend is observed in the overdamped mode. We also demonstrate that in addition to introducing particles, the reduction of particle distribution range equally contributes to increasing apparent viscosity of the ambient fluid. Finally, it is found that as the contact angle decreases, the damping ratio of droplet oscillations increases due to increased viscous dissipations and thus the maximum kinetic energy that the droplet can achieve decreases. As the particle distribution range increases, the effect of particles on droplet oscillations weakens, gradually making total kinetic energy and droplet deformation evolution curves for different contact angles indistinguishable.
{"title":"Numerical modeling of coalescence of two equal-sized droplets coated with particles","authors":"Hanlin Zhou , Ningjing Mao , Yong Liu , Hong Liang , Haihu Liu","doi":"10.1016/j.ijmultiphaseflow.2025.105554","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105554","url":null,"abstract":"<div><div>Coalescence dynamics of two equal-sized droplets coated with a fixed number of particles is numerically investigated using the lattice Boltzmann color-gradient model coupled with particle dynamics. By varying particle distribution range, we first show that the addition of particles can retard droplet deformation, and even in the absence of particles in the growth region of liquid bridge, more particles distributed at the axial ends of droplets significantly hinder droplet deformation. This is mainly because high kinetic energy region, which is concentrated at the axial ends of the droplet, is inhibited by particles in this region. We then vary the viscosity ratio of ambient fluid to droplet and find that for a moderate viscosity ratio, decreasing the particle distribution range causes the droplet oscillation mode to shift from critically damped to overdamped. In the under-damped mode, droplets are able to reach steady state earlier with a decrease in particle distribution range, while an opposite trend is observed in the overdamped mode. We also demonstrate that in addition to introducing particles, the reduction of particle distribution range equally contributes to increasing apparent viscosity of the ambient fluid. Finally, it is found that as the contact angle decreases, the damping ratio of droplet oscillations increases due to increased viscous dissipations and thus the maximum kinetic energy that the droplet can achieve decreases. As the particle distribution range increases, the effect of particles on droplet oscillations weakens, gradually making total kinetic energy and droplet deformation evolution curves for different contact angles indistinguishable.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"195 ","pages":"Article 105554"},"PeriodicalIF":3.8,"publicationDate":"2025-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145569382","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-17DOI: 10.1016/j.ijmultiphaseflow.2025.105550
Jonas Görtz, Andreas Jupke
Gas-evolving electrochemical processes, such as water-splitting, are heavily affected by the presence of gas bubbles. Detached electrogenerated bubbles alter electrolyte conductivity, and attached bubbles reduce the active electrode surface area. However, due to the complex interaction between gas bubbles and electrolyte flow, estimating gas phase fractions and flow patterns within membrane-separated parallel plate electrolyzers is challenging. Utilizing a partially transparent electrolyzer equipped with a 5k high-speed camera, this work applies particle image velocimetry (PIV) to capture time-averaged detailed flow fields across different current densities, superficial electrolyte velocities, heights, and electrode-membrane gaps. The findings reveal distinct flow regimes transforming from quasi-steady segregated flows under no net flow conditions into pseudo-turbulent flows with increased forced convection. Moreover, variations in current density, superficial electrolyte velocity, and electrode-membrane gap are shown to critically define the upward flow regime’s width and turbulence levels. Out of all studied parameters, we found the superficial electrolyte velocity to be the predominant factor for the width of the bubble curtain. The presented findings support understanding bubble-electrolyte interactions, flow patterns, and gas phase distribution in parallel-plate electrolyzers.
{"title":"Exploring the bubble-electrolyte interplay in membrane electrolyzers: PIV measurement of electrolyte flow regimes","authors":"Jonas Görtz, Andreas Jupke","doi":"10.1016/j.ijmultiphaseflow.2025.105550","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105550","url":null,"abstract":"<div><div>Gas-evolving electrochemical processes, such as water-splitting, are heavily affected by the presence of gas bubbles. Detached electrogenerated bubbles alter electrolyte conductivity, and attached bubbles reduce the active electrode surface area. However, due to the complex interaction between gas bubbles and electrolyte flow, estimating gas phase fractions and flow patterns within membrane-separated parallel plate electrolyzers is challenging. Utilizing a partially transparent electrolyzer equipped with a 5k high-speed camera, this work applies particle image velocimetry (PIV) to capture time-averaged detailed flow fields across different current densities, superficial electrolyte velocities, heights, and electrode-membrane gaps. The findings reveal distinct flow regimes transforming from quasi-steady segregated flows under no net flow conditions into pseudo-turbulent flows with increased forced convection. Moreover, variations in current density, superficial electrolyte velocity, and electrode-membrane gap are shown to critically define the upward flow regime’s width and turbulence levels. Out of all studied parameters, we found the superficial electrolyte velocity to be the predominant factor for the width of the bubble curtain. The presented findings support understanding bubble-electrolyte interactions, flow patterns, and gas phase distribution in parallel-plate electrolyzers.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"195 ","pages":"Article 105550"},"PeriodicalIF":3.8,"publicationDate":"2025-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145568897","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-17DOI: 10.1016/j.ijmultiphaseflow.2025.105548
Yicong Zhu, Yan Zhang, Ping Wang
The transport of sediment particles in turbulent flow is widespread in nature. The entrainment of bed particle represents the first step in forming and developing multiphase flow. According to the observed fact that the duration of fluid force acting on the particles is equally significant as its magnitude, event-based entrainment criterions have been developed to analyze the dynamical interactions between the particles and turbulence. However, these models, mainly based on wind tunnel or water channel experiments, only focus on the fluid forces and particle motions in two-dimensional plane (streamwise and vertical). Recent studies highlight the importance of spanwise fluid action, which depends on particle bed arrangement. In this work, the semi-resolved particle Lagrangian tracking method and direct numerical simulation of wall turbulence four-way coupled with particles are employed to simulate the rolling entrainment of individual particles for different bed arrangement and various Shields numbers. The simulation results illustrate that on specific bed arrangement, the spanwise fluid effect cannot be neglected and will lead to none-streamwise rolling entrainment. The fluid structures surrounding the particles during the entrainment process were analyzed, revealing that at lower Shields numbers, sweep events are the primary driving force for particle entrainment. Furthermore, for particles initiating motion in the spanwise direction, the conditional surrounding spanwise velocity field is asymmetrical and the spanwise structures are according the direction of motion. After simplifying the complex three-dimensional force/torque analysis by a projection method, a three-dimensional impulse criterion for particle entrainment was developed and validated by the numerical simulation results.
{"title":"Numerical study of particle rolling entrainment in wall turbulence on rough bed","authors":"Yicong Zhu, Yan Zhang, Ping Wang","doi":"10.1016/j.ijmultiphaseflow.2025.105548","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105548","url":null,"abstract":"<div><div>The transport of sediment particles in turbulent flow is widespread in nature. The entrainment of bed particle represents the first step in forming and developing multiphase flow. According to the observed fact that the duration of fluid force acting on the particles is equally significant as its magnitude, event-based entrainment criterions have been developed to analyze the dynamical interactions between the particles and turbulence. However, these models, mainly based on wind tunnel or water channel experiments, only focus on the fluid forces and particle motions in two-dimensional plane (streamwise and vertical). Recent studies highlight the importance of spanwise fluid action, which depends on particle bed arrangement. In this work, the semi-resolved particle Lagrangian tracking method and direct numerical simulation of wall turbulence four-way coupled with particles are employed to simulate the rolling entrainment of individual particles for different bed arrangement and various Shields numbers. The simulation results illustrate that on specific bed arrangement, the spanwise fluid effect cannot be neglected and will lead to none-streamwise rolling entrainment. The fluid structures surrounding the particles during the entrainment process were analyzed, revealing that at lower Shields numbers, sweep events are the primary driving force for particle entrainment. Furthermore, for particles initiating motion in the spanwise direction, the conditional surrounding spanwise velocity field is asymmetrical and the spanwise structures are according the direction of motion. After simplifying the complex three-dimensional force/torque analysis by a projection method, a three-dimensional impulse criterion for particle entrainment was developed and validated by the numerical simulation results.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"196 ","pages":"Article 105548"},"PeriodicalIF":3.8,"publicationDate":"2025-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145610440","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-17DOI: 10.1016/j.ijmultiphaseflow.2025.105552
Semyon A. Zdornikov, Sergey V. Isaenkov, Andrey V. Cherdantsev
Under low liquid loading, gas-liquid flow in a horizontal pipe has two main flow patterns: stratified and annular flows, which have significantly different integral characteristics such as pressure drop and heat transfer rate. Here we investigate transition between these flow patterns in a horizontal 20 mm pipe using working liquids with different viscosity and surface tension. Backlit visualization with background images is employed to distinguish the flow patterns and measure the height of liquid lifting. Brightness-Based Laser-Induced Fluorescence technique is used to measure film thickness and investigate spatiotemporal evolution of waves on film surface. Several unexpected observations were made. For large gas speeds, both reduced surface tension and increased viscosity facilitate upward climbing of thin liquid film and transition to annular flow. Circumferential spreading of disturbance waves is not directly related to the climbing of thin liquid film, and often shows opposite tendencies regarding the change in liquid properties. Transition to annular flow may occur in absence of disturbance waves, which confirms secondary role of large waves in liquid lifting. The liquid with low surface tension behaves as if it was more viscous, which might be related to intensive entrapment of gas bubbles by the liquid film.
{"title":"The effect of liquid properties on stratified-to-annular transition in a horizontal pipe","authors":"Semyon A. Zdornikov, Sergey V. Isaenkov, Andrey V. Cherdantsev","doi":"10.1016/j.ijmultiphaseflow.2025.105552","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105552","url":null,"abstract":"<div><div>Under low liquid loading, gas-liquid flow in a horizontal pipe has two main flow patterns: stratified and annular flows, which have significantly different integral characteristics such as pressure drop and heat transfer rate. Here we investigate transition between these flow patterns in a horizontal 20 mm pipe using working liquids with different viscosity and surface tension. Backlit visualization with background images is employed to distinguish the flow patterns and measure the height of liquid lifting. Brightness-Based Laser-Induced Fluorescence technique is used to measure film thickness and investigate spatiotemporal evolution of waves on film surface. Several unexpected observations were made. For large gas speeds, both reduced surface tension and increased viscosity facilitate upward climbing of thin liquid film and transition to annular flow. Circumferential spreading of disturbance waves is not directly related to the climbing of thin liquid film, and often shows opposite tendencies regarding the change in liquid properties. Transition to annular flow may occur in absence of disturbance waves, which confirms secondary role of large waves in liquid lifting. The liquid with low surface tension behaves as if it was more viscous, which might be related to intensive entrapment of gas bubbles by the liquid film.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"195 ","pages":"Article 105552"},"PeriodicalIF":3.8,"publicationDate":"2025-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145569380","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
扫码关注我们
求助内容：
应助结果提醒方式：
京公网安备 11010802042870号