Pub Date : 2025-10-30DOI: 10.1016/j.ijmultiphaseflow.2025.105508
Elham Mollaie, Rasool Mohammadi, Mohammad Ali Akhavan-Behabadi, Behrang Sajadi
This study attempts to establish versatile models, based on 30 flow pattern maps available in literature, employing machine learning (ML) methods, within range of database parameters, for adiabatic gas–liquid flow inside small-diameter tubes, from 0.53 to 5.16 mm. Support vector machines (SVM), artificial neural networks (ANN), and histogram-based gradient boosting (HGB) techniques are applied on two separate sets of carefully engineered input features, one with physical dimensional and one with dimensionless parameters, to see if dimensional reduction helps with providing better-performing models. The model training and testing procedure is conducted under a cross-validated study aiming to maximize the performance metric during hyperparameter tuning. The average accuracy of SVM, ANN, and HGB on test sets of data is reported as 0.9284, 0.9240, and 0.9620, respectively based on dimensional features. As for the dimensionless set, in the same order, values of 0.9115, 0.9115, and 0.9583 are obtained, indicating superior performance of HGB, along with acceptable results of ANN and SVM models. ANN models demonstrated faster prediction times than SVM and HGB, which makes ANN models more favorable for high-quantity prediction procedures. HGB models showed more robustness, while the SVM models showed the most prediction uncertainty amongst the models. Also, to visualize the model’s performance, several flow pattern maps are reconstructed with all models. Overall, due to the variety of flow behavior types in the database, employing sets of dimensionless numbers does not secure developing more general models and the performance for different input feature sets is roughly on par.
{"title":"Applied machine learning for adiabatic gas–liquid flow pattern prediction in small diameter circular tubes: Effect of dimensionality reduction","authors":"Elham Mollaie, Rasool Mohammadi, Mohammad Ali Akhavan-Behabadi, Behrang Sajadi","doi":"10.1016/j.ijmultiphaseflow.2025.105508","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105508","url":null,"abstract":"<div><div>This study attempts to establish versatile models, based on 30 flow pattern maps available in literature, employing machine learning (ML) methods, within range of database parameters, for adiabatic gas–liquid flow inside small-diameter tubes, from 0.53 to 5.16 mm. Support vector machines (SVM), artificial neural networks (ANN), and histogram-based gradient boosting (HGB) techniques are applied on two separate sets of carefully engineered input features, one with physical dimensional and one with dimensionless parameters, to see if dimensional reduction helps with providing better-performing models. The model training and testing procedure is conducted under a cross-validated study aiming to maximize the performance metric during hyperparameter tuning. The average accuracy of SVM, ANN, and HGB on test sets of data is reported as 0.9284, 0.9240, and 0.9620, respectively based on dimensional features. As for the dimensionless set, in the same order, values of 0.9115, 0.9115, and 0.9583 are obtained, indicating superior performance of HGB, along with acceptable results of ANN and SVM models. ANN models demonstrated faster prediction times than SVM and HGB, which makes ANN models more favorable for high-quantity prediction procedures. HGB models showed more robustness, while the SVM models showed the most prediction uncertainty amongst the models. Also, to visualize the model’s performance, several flow pattern maps are reconstructed with all models. Overall, due to the variety of flow behavior types in the database, employing sets of dimensionless numbers does not secure developing more general models and the performance for different input feature sets is roughly on par.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"195 ","pages":"Article 105508"},"PeriodicalIF":3.8,"publicationDate":"2025-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145464111","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 : 2025-10-30DOI: 10.1016/j.ijmultiphaseflow.2025.105506
Hong-Wei Xiao, Jie Wu
The present study examines the impact behavior of air-in-liquid compound droplets on curved surfaces using a numerical approach. By integrating the lattice Boltzmann method (LBM) for multiphase flow modeling and the immersed boundary method (IBM) for fluid-substrate interactions, we systematically investigate the influence of surface diameter and inner bubble size on the dynamics of droplet impact. Key parameters analyzed include liquid film thickness, bubble deformation, splash morphology, rupture mechanisms, impact force and pressure. Our findings reveal several significant conclusions: (1) Surface diameter and inner bubble size exhibit opposing effects on splash length and cavity formation. (2) The splashing angle at rupture is correlated with single-phase droplet behavior and surface diameter, showing minimal dependence on bubble size. (3) Three distinct rupture mechanisms emerge during the spreading phase, influenced by interactions between surface diameter and inner bubble size, with potential hybrid manifestations observed. (4) The maximum impact force is primarily determined by inner bubble size, with smaller bubbles demonstrating enhanced impact buffering capabilities. (5) The developed models for maximum impact force and pressure show excellent agreement with numerical simulations. These findings provide valuable insights into the control of droplet dynamics, offering practical applications in fields ranging from spray coating to biomedical engineering.
{"title":"Impact of air-in-liquid compound droplet on a curved surface","authors":"Hong-Wei Xiao, Jie Wu","doi":"10.1016/j.ijmultiphaseflow.2025.105506","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105506","url":null,"abstract":"<div><div>The present study examines the impact behavior of air-in-liquid compound droplets on curved surfaces using a numerical approach. By integrating the lattice Boltzmann method (LBM) for multiphase flow modeling and the immersed boundary method (IBM) for fluid-substrate interactions, we systematically investigate the influence of surface diameter and inner bubble size on the dynamics of droplet impact. Key parameters analyzed include liquid film thickness, bubble deformation, splash morphology, rupture mechanisms, impact force and pressure. Our findings reveal several significant conclusions: (1) Surface diameter and inner bubble size exhibit opposing effects on splash length and cavity formation. (2) The splashing angle at rupture is correlated with single-phase droplet behavior and surface diameter, showing minimal dependence on bubble size. (3) Three distinct rupture mechanisms emerge during the spreading phase, influenced by interactions between surface diameter and inner bubble size, with potential hybrid manifestations observed. (4) The maximum impact force is primarily determined by inner bubble size, with smaller bubbles demonstrating enhanced impact buffering capabilities. (5) The developed models for maximum impact force and pressure show excellent agreement with numerical simulations. These findings provide valuable insights into the control of droplet dynamics, offering practical applications in fields ranging from spray coating to biomedical engineering.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"195 ","pages":"Article 105506"},"PeriodicalIF":3.8,"publicationDate":"2025-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145464012","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 : 2025-10-30DOI: 10.1016/j.ijmultiphaseflow.2025.105505
Davide Procacci , Arturo A. Arosemena , Simone Di Giorgio , Jannike Solsvik
The effect of buoyant bubbles – undergoing deformation, breakup, and coalescence – on wall-bounded turbulence is explored through numerical simulations of a bubbly channel flow in an upwards configuration. We show that the dispersed phase drastically changes the turbulence intensities. In particular, we demonstrate that while bubbles increase anisotropy in the core region, most of the channel exhibits a higher degree of isotropy compared to the single-phase flow. We attribute this energy redistribution to an increase in sweeps, driven by the turbulent wakes and shear layers generated by the largest bubbles. These findings pave the way for a better understanding of bubble-laden flows and offer valuable data for validating Reynolds stress models.
{"title":"Turbulence anisotropy modulation in bubble-laden channel flow: A numerical study","authors":"Davide Procacci , Arturo A. Arosemena , Simone Di Giorgio , Jannike Solsvik","doi":"10.1016/j.ijmultiphaseflow.2025.105505","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105505","url":null,"abstract":"<div><div>The effect of buoyant bubbles – undergoing deformation, breakup, and coalescence – on wall-bounded turbulence is explored through numerical simulations of a bubbly channel flow in an upwards configuration. We show that the dispersed phase drastically changes the turbulence intensities. In particular, we demonstrate that while bubbles increase anisotropy in the core region, most of the channel exhibits a higher degree of isotropy compared to the single-phase flow. We attribute this energy redistribution to an increase in sweeps, driven by the turbulent wakes and shear layers generated by the largest bubbles. These findings pave the way for a better understanding of bubble-laden flows and offer valuable data for validating Reynolds stress models.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"195 ","pages":"Article 105505"},"PeriodicalIF":3.8,"publicationDate":"2025-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145414611","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 : 2025-10-28DOI: 10.1016/j.ijmultiphaseflow.2025.105504
Long Ju , Chunyu Zhang , Bicheng Yan , Shuyu Sun
This paper proposes a lattice Boltzmann (LB) wetting boundary processing scheme for binary flow with large density ratios. The greatest advantage of the proposed method is that the implementation of contact line motion can be significantly simplified while still maintaining good accuracy and locality. For this purpose, the order parameter gradient at the boundary node is derived by combining the wetting boundary conditions in the form of free energy with the form of geometry, and the information of the contact angle is explicitly incorporated into the expression of the chemical potential, thus avoiding complicated interpolations for irregular geometries. In addition, by introducing free parameters, the relaxation time is decoupled from the viscosity, thereby enhancing the numerical stability of the scheme under conditions of high Reynolds numbers. Several numerical testing cases are conducted, including wetting processes on straight and curved boundaries. The results demonstrate that the proposed method has good ability and satisfactory accuracy to simulate contact line motions.
{"title":"Phase-field based lattice Boltzmann modeling of contact angles in binary flow with large density ratios","authors":"Long Ju , Chunyu Zhang , Bicheng Yan , Shuyu Sun","doi":"10.1016/j.ijmultiphaseflow.2025.105504","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105504","url":null,"abstract":"<div><div>This paper proposes a lattice Boltzmann (LB) wetting boundary processing scheme for binary flow with large density ratios. The greatest advantage of the proposed method is that the implementation of contact line motion can be significantly simplified while still maintaining good accuracy and locality. For this purpose, the order parameter gradient at the boundary node is derived by combining the wetting boundary conditions in the form of free energy with the form of geometry, and the information of the contact angle is explicitly incorporated into the expression of the chemical potential, thus avoiding complicated interpolations for irregular geometries. In addition, by introducing free parameters, the relaxation time is decoupled from the viscosity, thereby enhancing the numerical stability of the scheme under conditions of high Reynolds numbers. Several numerical testing cases are conducted, including wetting processes on straight and curved boundaries. The results demonstrate that the proposed method has good ability and satisfactory accuracy to simulate contact line motions.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"195 ","pages":"Article 105504"},"PeriodicalIF":3.8,"publicationDate":"2025-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145414686","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}
<div><div>Convection-driven separation in binary fluid mixtures is crucial in applications ranging from geothermal energy to chemical processing. However, prior studies have largely neglected the combined influence of the Soret and Dufour effects on species redistribution. This paper investigates convection-driven separation in a binary fluid mixture within a porous medium, incorporating the Soret effect and, for the first time, systematically evaluating the influence of the Dufour effect. Using a combination of analytical and numerical methods, this study assesses the impact of the Dufour parameter on both the onset of convection and the resulting species separation within a shallow porous cavity. Linear and nonlinear analyses are employed to determine thresholds for stationary, oscillatory, and subcritical bifurcations with respect to key parameters: the Dufour number (<span><math><mrow><mi>D</mi><mi>f</mi></mrow></math></span>), the separation ratio (<span><math><mi>φ</mi></math></span>), the Lewis number (<span><math><mrow><mi>L</mi><mi>e</mi></mrow></math></span>), the thermal Rayleigh number (<span><math><msub><mi>R</mi><mi>T</mi></msub></math></span>), and the Darcy number (<span><math><mrow><mi>D</mi><mi>a</mi></mrow></math></span>). An analytical solution based on the parallel flow approximation is developed and validated numerically using a finite-difference method to evaluate species separation and heat transfer characteristics. Three regimes are examined: Darcy, Brinkman, and pure fluid media. The analysis spans a wide range of Lewis numbers (<span><math><mrow><mi>L</mi><mi>e</mi></mrow></math></span> = 0.1 to 100), covering gases, hydrocarbon fuels, and salt-water solutions. Results show that the Dufour effect significantly influences species separation in gaseous mixtures, while its impact on liquid mixtures is negligible. The findings demonstrate that within the Darcy regime, low permeability effectively suppresses convective flows, thereby enhancing species separation more effectively than in the Brinkman or pure fluid regimes, where higher permeability promotes stronger convection and reduces separation efficiency. Moreover, a low-permeability Darcy medium, combined with a negative Dufour number and minimal thermal gradients, provides the most favorable conditions for maximizing species separation. Results show that for <span><math><mrow><mi>L</mi><mi>e</mi><mo>=</mo><mn>2</mn></mrow></math></span>, 10 and 100, increasing <span><math><mrow><mi>D</mi><mi>f</mi></mrow></math></span> from -0.2 to 0.2 reduces species separation by <span><math><mrow><mn>23.15</mn><mo>%</mo><mo>,</mo></mrow></math></span> <span><math><mrow><mn>9</mn><mo>%</mo></mrow></math></span> and <span><math><mrow><mn>0.00</mn><mo>%</mo><mo>,</mo></mrow></math></span> respectively. This confirms the minimal impact of the Dufour effect on liquid mixtures (high <span><math><mrow><mi>L</mi><mi>e</mi></mrow></math></span>). Negative <span><math><mrow><mi>D</mi><mi>f</
{"title":"Influence of the dufour effect on soret-driven species separation in binary mixtures: A comparative numerical and analytical study across porous flow regimes","authors":"Ismail Filahi , Layla Foura , Mohamed Bourich , Youssef Dahani , Safae Hasnaoui , Abdelfattah El Mansouri , Abdelkhalek Amahmid , Mohammed Hasnaoui","doi":"10.1016/j.ijmultiphaseflow.2025.105501","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105501","url":null,"abstract":"<div><div>Convection-driven separation in binary fluid mixtures is crucial in applications ranging from geothermal energy to chemical processing. However, prior studies have largely neglected the combined influence of the Soret and Dufour effects on species redistribution. This paper investigates convection-driven separation in a binary fluid mixture within a porous medium, incorporating the Soret effect and, for the first time, systematically evaluating the influence of the Dufour effect. Using a combination of analytical and numerical methods, this study assesses the impact of the Dufour parameter on both the onset of convection and the resulting species separation within a shallow porous cavity. Linear and nonlinear analyses are employed to determine thresholds for stationary, oscillatory, and subcritical bifurcations with respect to key parameters: the Dufour number (<span><math><mrow><mi>D</mi><mi>f</mi></mrow></math></span>), the separation ratio (<span><math><mi>φ</mi></math></span>), the Lewis number (<span><math><mrow><mi>L</mi><mi>e</mi></mrow></math></span>), the thermal Rayleigh number (<span><math><msub><mi>R</mi><mi>T</mi></msub></math></span>), and the Darcy number (<span><math><mrow><mi>D</mi><mi>a</mi></mrow></math></span>). An analytical solution based on the parallel flow approximation is developed and validated numerically using a finite-difference method to evaluate species separation and heat transfer characteristics. Three regimes are examined: Darcy, Brinkman, and pure fluid media. The analysis spans a wide range of Lewis numbers (<span><math><mrow><mi>L</mi><mi>e</mi></mrow></math></span> = 0.1 to 100), covering gases, hydrocarbon fuels, and salt-water solutions. Results show that the Dufour effect significantly influences species separation in gaseous mixtures, while its impact on liquid mixtures is negligible. The findings demonstrate that within the Darcy regime, low permeability effectively suppresses convective flows, thereby enhancing species separation more effectively than in the Brinkman or pure fluid regimes, where higher permeability promotes stronger convection and reduces separation efficiency. Moreover, a low-permeability Darcy medium, combined with a negative Dufour number and minimal thermal gradients, provides the most favorable conditions for maximizing species separation. Results show that for <span><math><mrow><mi>L</mi><mi>e</mi><mo>=</mo><mn>2</mn></mrow></math></span>, 10 and 100, increasing <span><math><mrow><mi>D</mi><mi>f</mi></mrow></math></span> from -0.2 to 0.2 reduces species separation by <span><math><mrow><mn>23.15</mn><mo>%</mo><mo>,</mo></mrow></math></span> <span><math><mrow><mn>9</mn><mo>%</mo></mrow></math></span> and <span><math><mrow><mn>0.00</mn><mo>%</mo><mo>,</mo></mrow></math></span> respectively. This confirms the minimal impact of the Dufour effect on liquid mixtures (high <span><math><mrow><mi>L</mi><mi>e</mi></mrow></math></span>). Negative <span><math><mrow><mi>D</mi><mi>f</","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"195 ","pages":"Article 105501"},"PeriodicalIF":3.8,"publicationDate":"2025-10-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145414687","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 : 2025-10-27DOI: 10.1016/j.ijmultiphaseflow.2025.105499
Faraz Salimnezhad, Metin Muradoglu
Evaporation of a deformable droplet under convection is investigated and performance of the classical and Abramzon–Sirignano (A–S) models is evaluated. Using the Immersed Boundary/Front-Tracking (IB/FT) method, interface-resolved simulations are performed to examine droplet evaporation dynamics over a wide range of Reynolds (), Weber (), and mass transfer () numbers. It is shown that flow in the wake region is greatly influenced by the Stefan flow as higher evaporation rates leads to an earlier flow separation and a larger recirculation zone behind the droplet. Under strong convection, the models fail to capture the evaporation rate especially in the wake region, which leads to significant discrepancies compared to interface-resolved simulations. Droplet deformation greatly influences the flow field around the droplet and generally enhances evaporation but the evaporation rate remains well correlated with the surface area. The A–S model exhibits a reasonably good performance for a nearly spherical droplet but its performance deteriorates significantly and generally underpredicts evaporation rate as droplet deformation increases. The A–S model is overall found to outperform the classical model in the presence of significant convection.
{"title":"Computational investigation of deformable droplet evaporation under forced convection","authors":"Faraz Salimnezhad, Metin Muradoglu","doi":"10.1016/j.ijmultiphaseflow.2025.105499","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105499","url":null,"abstract":"<div><div>Evaporation of a deformable droplet under convection is investigated and performance of the classical and Abramzon–Sirignano (A–S) models is evaluated. Using the Immersed Boundary/Front-Tracking (IB/FT) method, interface-resolved simulations are performed to examine droplet evaporation dynamics over a wide range of Reynolds (<span><math><mrow><mn>20</mn><mo>≤</mo><mi>R</mi><mi>e</mi><mo>≤</mo><mn>200</mn></mrow></math></span>), Weber (<span><math><mrow><mn>0</mn><mo>.</mo><mn>65</mn><mo>≤</mo><mi>W</mi><mi>e</mi><mo>≤</mo><mn>9</mn></mrow></math></span>), and mass transfer (<span><math><mrow><mn>1</mn><mo>≤</mo><msub><mrow><mi>B</mi></mrow><mrow><mi>M</mi></mrow></msub><mo>≤</mo><mn>15</mn></mrow></math></span>) numbers. It is shown that flow in the wake region is greatly influenced by the Stefan flow as higher evaporation rates leads to an earlier flow separation and a larger recirculation zone behind the droplet. Under strong convection, the models fail to capture the evaporation rate especially in the wake region, which leads to significant discrepancies compared to interface-resolved simulations. Droplet deformation greatly influences the flow field around the droplet and generally enhances evaporation but the evaporation rate remains well correlated with the surface area. The A–S model exhibits a reasonably good performance for a nearly spherical droplet but its performance deteriorates significantly and generally underpredicts evaporation rate as droplet deformation increases. The A–S model is overall found to outperform the classical model in the presence of significant convection.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"195 ","pages":"Article 105499"},"PeriodicalIF":3.8,"publicationDate":"2025-10-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145414605","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 : 2025-10-24DOI: 10.1016/j.ijmultiphaseflow.2025.105498
Jongsu Jeong, Seungho Kim
While droplet rebound is typically observed on hydrophobic or textured surfaces, this study provides experimental and numerical evidence that, consistent with prior studies, smooth superhydrophilic surfaces can exhibit bouncing when a thin intervening air film remains intact during impact. Through a combination of experiments, numerical simulations, and theoretical modeling, we show that the persistence of this air film plays a critical role in governing the rebound dynamics. High-speed imaging and interferometry reveal three distinct regimes — bouncing, partial bouncing, and spreading — depending on impact conditions. A key parameter identified is the lifetime of the air film, which has hitherto been unreported and is experimentally found to decrease as impact inertia increases. We develop a scaling model based on fluid–structure interaction within the gas layer, predicting the rupturetime scale of air film that sensitively depends on the Weber number. The rupture time derived from this model shows agreement with experimental measurements, thereby capturing the overall experimental trends. Using this model, three regimes can be identified by rupture timing: bouncing when no rupture occurs during contact, partial bouncing when rupture occurs near the end of contact, and spreading when rupture occurs almost immediately. These findings highlight the central role of air film dynamics in rebound behavior on superhydrophilic surfaces and might suggest design principles for controlling liquid repellency through vapor-phase engineering.
{"title":"Air film-mediated drop bouncing on superhydrophilic surfaces","authors":"Jongsu Jeong, Seungho Kim","doi":"10.1016/j.ijmultiphaseflow.2025.105498","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105498","url":null,"abstract":"<div><div>While droplet rebound is typically observed on hydrophobic or textured surfaces, this study provides experimental and numerical evidence that, consistent with prior studies, smooth superhydrophilic surfaces can exhibit bouncing when a thin intervening air film remains intact during impact. Through a combination of experiments, numerical simulations, and theoretical modeling, we show that the persistence of this air film plays a critical role in governing the rebound dynamics. High-speed imaging and interferometry reveal three distinct regimes — bouncing, partial bouncing, and spreading — depending on impact conditions. A key parameter identified is the lifetime of the air film, which has hitherto been unreported and is experimentally found to decrease as impact inertia increases. We develop a scaling model based on fluid–structure interaction within the gas layer, predicting the rupturetime scale of air film that sensitively depends on the Weber number. The rupture time derived from this model shows agreement with experimental measurements, thereby capturing the overall experimental trends. Using this model, three regimes can be identified by rupture timing: bouncing when no rupture occurs during contact, partial bouncing when rupture occurs near the end of contact, and spreading when rupture occurs almost immediately. These findings highlight the central role of air film dynamics in rebound behavior on superhydrophilic surfaces and might suggest design principles for controlling liquid repellency through vapor-phase engineering.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"195 ","pages":"Article 105498"},"PeriodicalIF":3.8,"publicationDate":"2025-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145371329","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 : 2025-10-24DOI: 10.1016/j.ijmultiphaseflow.2025.105500
Jinhua Lu, Thomas Gregorczyk, Song Zhao, Pierre Boivin
The multiphase lattice Boltzmann models face two main challenges: deviation terms in the recovered momentum equation and limited numerical stability at large density ratios, Reynolds numbers, and Weber numbers, which remain difficult to address simultaneously. This paper proposes three recursive regularized multiphase lattice Boltzmann models to address the two challenges. They can eliminate the deviation terms in the recovered momentum equation and adopt different pressure schemes. Detailed numerical tests are conducted to test their numerical stability and accuracy performance. The three models exhibit good numerical stability in an extensive range of density and viscosity ratios, significantly better than the single-relaxation-time multiphase lattice Boltzmann model with deviation terms in the recovered momentum equation. In addition, it is found that the dissipation terms in the pressure scheme should be consistent with the continuous pressure equation, which is decoupled from density and viscosity variations, to obtain correct velocity profiles for transient flow with large density and viscosity variations. The recursive regularized multiphase lattice Boltzmann model with a consistent pressure scheme that is decoupled from density and viscosity variations can achieve superior numerical stability and accuracy.
{"title":"Phase-field-based recursive regularized multiphase lattice Boltzmann model with a consistent pressure scheme","authors":"Jinhua Lu, Thomas Gregorczyk, Song Zhao, Pierre Boivin","doi":"10.1016/j.ijmultiphaseflow.2025.105500","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105500","url":null,"abstract":"<div><div>The multiphase lattice Boltzmann models face two main challenges: deviation terms in the recovered momentum equation and limited numerical stability at large density ratios, Reynolds numbers, and Weber numbers, which remain difficult to address simultaneously. This paper proposes three recursive regularized multiphase lattice Boltzmann models to address the two challenges. They can eliminate the deviation terms in the recovered momentum equation and adopt different pressure schemes. Detailed numerical tests are conducted to test their numerical stability and accuracy performance. The three models exhibit good numerical stability in an extensive range of density and viscosity ratios, significantly better than the single-relaxation-time multiphase lattice Boltzmann model with deviation terms in the recovered momentum equation. In addition, it is found that the dissipation terms in the pressure scheme should be consistent with the continuous pressure equation, which is decoupled from density and viscosity variations, to obtain correct velocity profiles for transient flow with large density and viscosity variations. The recursive regularized multiphase lattice Boltzmann model with a consistent pressure scheme that is decoupled from density and viscosity variations can achieve superior numerical stability and accuracy.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"195 ","pages":"Article 105500"},"PeriodicalIF":3.8,"publicationDate":"2025-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145414606","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 : 2025-10-24DOI: 10.1016/j.ijmultiphaseflow.2025.105502
Qiao-Zhong Li , Hou-Biao Ma , You Li , Xiang Li
This study proposes a generalized conservative phase-field-based simplified multiphase lattice Boltzmann framework for simulation of N-phase flows with immiscible incompressible fluids. In this model, the generalized conservative phase field equations and the hydrodynamics equations are solved by reconstructing solutions within the LB framework with prediction-correction step based on a fractional-step method. Compared to the conventional lattice Boltzmann modeling, the present numerical strategy significantly decreases the number of variables at each grid point, resulting in lower memory consumption that proves particularly advantageous for multiphase systems with N immiscible incompressible fluids. Meanwhile, the framework enables direct implementation of physical boundary conditions without requiring complex transformations between macroscopic constraints and distribution functions. Notably, the model preserves the mesoscopic kinetic fidelity characteristic inherent to the conventional lattice Boltzmann method and integrates robust numerical stability through the matured fractional-step technique and reconstruction strategy. Several numerical experiments, such as three side-by-side stationary droplets, triply concentric droplets system, the morphology of compound droplet and the spreading dynamic of liquid lenses with large density ratios, are conducted to verify the model effectiveness in calculating surface tension and describing the N-phase interfacial dynamic. The model’s capability to handle the multi-physics field coupling is further demonstrated through simulations of electrohydrodynamic deformation of compound droplets, confirming its applicability to complex N-phase systems with interfacial phenomena and external field interactions. Lastly, the present model is employed to study droplet impact on thin liquid films, demonstrating its robustness and versatility in simulating dynamic fluid flow phenomena.
{"title":"Simplified multiphase Lattice Boltzmann framework with generalized conservative phase-field modeling for N-phase immiscible flows","authors":"Qiao-Zhong Li , Hou-Biao Ma , You Li , Xiang Li","doi":"10.1016/j.ijmultiphaseflow.2025.105502","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105502","url":null,"abstract":"<div><div>This study proposes a generalized conservative phase-field-based simplified multiphase lattice Boltzmann framework for simulation of N-phase flows with immiscible incompressible fluids. In this model, the generalized conservative phase field equations and the hydrodynamics equations are solved by reconstructing solutions within the LB framework with prediction-correction step based on a fractional-step method. Compared to the conventional lattice Boltzmann modeling, the present numerical strategy significantly decreases the number of variables at each grid point, resulting in lower memory consumption that proves particularly advantageous for multiphase systems with N immiscible incompressible fluids. Meanwhile, the framework enables direct implementation of physical boundary conditions without requiring complex transformations between macroscopic constraints and distribution functions. Notably, the model preserves the mesoscopic kinetic fidelity characteristic inherent to the conventional lattice Boltzmann method and integrates robust numerical stability through the matured fractional-step technique and reconstruction strategy. Several numerical experiments, such as three side-by-side stationary droplets, triply concentric droplets system, the morphology of compound droplet and the spreading dynamic of liquid lenses with large density ratios, are conducted to verify the model effectiveness in calculating surface tension and describing the N-phase interfacial dynamic. The model’s capability to handle the multi-physics field coupling is further demonstrated through simulations of electrohydrodynamic deformation of compound droplets, confirming its applicability to complex N-phase systems with interfacial phenomena and external field interactions. Lastly, the present model is employed to study droplet impact on thin liquid films, demonstrating its robustness and versatility in simulating dynamic fluid flow phenomena.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"195 ","pages":"Article 105502"},"PeriodicalIF":3.8,"publicationDate":"2025-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145414610","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 : 2025-10-23DOI: 10.1016/j.ijmultiphaseflow.2025.105494
Jiaying Gu , Qiuyi Wang , Yawen Gao , Lei Yi , Yunqiao Liu , Mingbo Li , Benlong Wang
Bubbly flow underpins many engineering processes by providing vast interfacial area for mass and heat exchange. This work presents a comprehensive investigation of microbubble generation, transport, and breakup within a self-suction Venturi channel employing experiments and numerical simulation. By systematically varying liquid Reynolds number and air-sucking orifice diameters, we observed a sequence of distinct flow regimes: from laminar annular flow and interfacial instabilities through shear-driven bubble entrainment to bubbly flow with cavitation-bubble shedding. Statistical analysis reveals that bubble size distributions collapse onto log-normal profiles, indicating a cascade of multiplicative breakup events, and that mean bubble diameter scales linearly with the maximum stable diameter across all geometries, demonstrating the universality of turbulent fragmentation dynamics. As flow strength increases, the mean bubble diameter decreases sharply before leveling off under small-scale turbulence, while the maximum bubble size continues to diminish steadily. Accordingly, the scaling laws between the average/maximum sizes of the bubble population and the liquid Reynolds number have been revealed. These findings reveal that microbubble dynamics in Venturi flows arise from a confluence of mechanisms—classical inertial–capillary breakup at the Hinze scale, shear-off near walls, anisotropic dissipation, and extended residence in recirculation zones. This comprehensive picture advances our ability to predict microbubble characteristics for optimized mass transfer and mixing in industrial applications.
{"title":"Flow characteristics and microbubble formation in turbulent mixing of a self-sucking Venturi channel","authors":"Jiaying Gu , Qiuyi Wang , Yawen Gao , Lei Yi , Yunqiao Liu , Mingbo Li , Benlong Wang","doi":"10.1016/j.ijmultiphaseflow.2025.105494","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105494","url":null,"abstract":"<div><div>Bubbly flow underpins many engineering processes by providing vast interfacial area for mass and heat exchange. This work presents a comprehensive investigation of microbubble generation, transport, and breakup within a self-suction Venturi channel employing experiments and numerical simulation. By systematically varying liquid Reynolds number and air-sucking orifice diameters, we observed a sequence of distinct flow regimes: from laminar annular flow and interfacial instabilities through shear-driven bubble entrainment to bubbly flow with cavitation-bubble shedding. Statistical analysis reveals that bubble size distributions collapse onto log-normal profiles, indicating a cascade of multiplicative breakup events, and that mean bubble diameter scales linearly with the maximum stable diameter across all geometries, demonstrating the universality of turbulent fragmentation dynamics. As flow strength increases, the mean bubble diameter decreases sharply before leveling off under small-scale turbulence, while the maximum bubble size continues to diminish steadily. Accordingly, the scaling laws between the average/maximum sizes of the bubble population and the liquid Reynolds number have been revealed. These findings reveal that microbubble dynamics in Venturi flows arise from a confluence of mechanisms—classical inertial–capillary breakup at the Hinze scale, shear-off near walls, anisotropic dissipation, and extended residence in recirculation zones. This comprehensive picture advances our ability to predict microbubble characteristics for optimized mass transfer and mixing in industrial applications.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"194 ","pages":"Article 105494"},"PeriodicalIF":3.8,"publicationDate":"2025-10-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145358133","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}
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