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}
Pub Date : 2025-10-22DOI: 10.1016/j.ijmultiphaseflow.2025.105497
Jiajun Jiao , Yunhui Sun , Menghan Pan , Pengfei Lv , Junli He , Qingquan Liu , Yi An , Xiaoliang Wang
This study experimentally investigated the dense particle-liquid open channel flows over smooth and rough inclined beds using the refractive index matching (RIM) technique. The internal flow profiles of the granular phase, including velocity, shear rate, granular temperature, and solid concentration, were reconstructed through image processing techniques. The vertical stratification behavior of dense particle-liquid channel flows under various inclination angles and inflow heights was examined. Results indicated that four fundamental local flow states exist in dense particle-liquid channel flows: plug flow, ordered friction flow, disordered friction flow, and collision flow. These flow states can be combined to construct the stratification flow in the granular phase of two-phase dense granular flows. There are three flowing superimposed modes on the smooth bed: plug flow, disordered friction flow + plug flow, and disordered friction flow. We identified three typical superimposed flow modes on the rough bed: ordered friction flow + disordered friction flow (OF-DF flow), collision flow + disordered friction flow (C-DF flow), and collision flow + disordered friction flow + plug flow (C-DF-P flow). The complex flow structure observed under various operating conditions is simplified through the superposition of the fundamental local flow states. This study significantly advances the understanding of the intricate internal flow behavior and structure of dense particle-liquid two-phase flows.
{"title":"Vertical stratification and local flow states of dense particle-liquid inclined open channel flow based on internal observation","authors":"Jiajun Jiao , Yunhui Sun , Menghan Pan , Pengfei Lv , Junli He , Qingquan Liu , Yi An , Xiaoliang Wang","doi":"10.1016/j.ijmultiphaseflow.2025.105497","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105497","url":null,"abstract":"<div><div>This study experimentally investigated the dense particle-liquid open channel flows over smooth and rough inclined beds using the refractive index matching (RIM) technique. The internal flow profiles of the granular phase, including velocity, shear rate, granular temperature, and solid concentration, were reconstructed through image processing techniques. The vertical stratification behavior of dense particle-liquid channel flows under various inclination angles and inflow heights was examined. Results indicated that four fundamental local flow states exist in dense particle-liquid channel flows: plug flow, ordered friction flow, disordered friction flow, and collision flow. These flow states can be combined to construct the stratification flow in the granular phase of two-phase dense granular flows. There are three flowing superimposed modes on the smooth bed: plug flow, disordered friction flow + plug flow, and disordered friction flow. We identified three typical superimposed flow modes on the rough bed: ordered friction flow + disordered friction flow (OF-DF flow), collision flow + disordered friction flow (C-DF flow), and collision flow + disordered friction flow + plug flow (C-DF-P flow). The complex flow structure observed under various operating conditions is simplified through the superposition of the fundamental local flow states. This study significantly advances the understanding of the intricate internal flow behavior and structure of dense particle-liquid two-phase flows.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"195 ","pages":"Article 105497"},"PeriodicalIF":3.8,"publicationDate":"2025-10-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145414608","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 : 2025-10-22DOI: 10.1016/j.ijmultiphaseflow.2025.105495
Théo Rajim, Yedhir Mezache, Bastien Di Pierro, Pierre Trontin
The dynamics of bubble and droplet coalescence and repulsion are critical in a variety of natural and industrial multiphase systems. Their direct numerical simulation (DNS) remains challenging due to the multiscale nature of interfacial interactions. This study presents a mesoscale numerical approach that incorporates a repulsive disjoining pressure into an Eulerian framework to model near-contact interactions without explicitly resolving nanoscale forces. The method computes interfacial distances through a transport equation, enabling efficient and scalable implementation across parallel computing architectures. Unlike traditional marker-based or interface-tracking methods, the approach is independent of the number of bubbles or droplets in the domain. The method is validated on representative test cases, including droplet collisions and static foam networks, and is shown to accurately capture both dynamic inertial effects and quasi-static configurations. Notably, it enables DNS of wet foams with reduced liquid fractions compared to conventional level-set methods where repulsive interactions are not accounted for. This approach lays the foundation for simulating more realistic foam structures and analyzing destabilization phenomena such as drainage and coarsening, thus contributing to the predictive modeling of complex gas–liquid systems.
{"title":"A mesoscale Eulerian numerical method for short-range repulsion in interfacial dynamics","authors":"Théo Rajim, Yedhir Mezache, Bastien Di Pierro, Pierre Trontin","doi":"10.1016/j.ijmultiphaseflow.2025.105495","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105495","url":null,"abstract":"<div><div>The dynamics of bubble and droplet coalescence and repulsion are critical in a variety of natural and industrial multiphase systems. Their direct numerical simulation (DNS) remains challenging due to the multiscale nature of interfacial interactions. This study presents a mesoscale numerical approach that incorporates a repulsive disjoining pressure into an Eulerian framework to model near-contact interactions without explicitly resolving nanoscale forces. The method computes interfacial distances through a transport equation, enabling efficient and scalable implementation across parallel computing architectures. Unlike traditional marker-based or interface-tracking methods, the approach is independent of the number of bubbles or droplets in the domain. The method is validated on representative test cases, including droplet collisions and static foam networks, and is shown to accurately capture both dynamic inertial effects and quasi-static configurations. Notably, it enables DNS of wet foams with reduced liquid fractions compared to conventional level-set methods where repulsive interactions are not accounted for. This approach lays the foundation for simulating more realistic foam structures and analyzing destabilization phenomena such as drainage and coarsening, thus contributing to the predictive modeling of complex gas–liquid systems.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"194 ","pages":"Article 105495"},"PeriodicalIF":3.8,"publicationDate":"2025-10-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145358059","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 : 2025-10-21DOI: 10.1016/j.ijmultiphaseflow.2025.105496
Jingbo Ji , Hao Zhang , Xizhong An , Dongmin Yang , Jiang Chen
In this paper, the torque, rotation, and orientation of cylindrical particles in the shear-thinning shear flow are investigated using particle-resolved direct numerical simulation. Results show that compared to Newtonian fluids, the shear-thinning properties of shear-thinning fluids significantly decrease the torque of fixed particles. For cylindrical particles rotating about a fixed axis, the shear-thinning properties significantly decrease the equilibrium orientation angle and rotational velocity of the particles. The rotational modes of particles reaching the equilibrium state can be divided into single direction rotation and damped oscillatory rotation, respectively. The increase in shear-thinning properties and the decrease in shear strength can exacerbate the damped oscillatory phenomenon. The equilibrium orientation angle and rotational velocity increase with the aspect ratio, and the former is independent of the initial orientation. The dimensionless predictive correlations of torque coefficient and equilibrium orientation angle are established within the current parameter range. The results indicate that shear-thinning properties and shear strength are crucial for particle rotation, and these findings provide guidance for predicting and controlling the rotation and orientation of the cylindrical particles.
{"title":"Torque induced rotation of cylindrical particles in shear-thinning fluids: Effects of fluid properties and particle configuration","authors":"Jingbo Ji , Hao Zhang , Xizhong An , Dongmin Yang , Jiang Chen","doi":"10.1016/j.ijmultiphaseflow.2025.105496","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105496","url":null,"abstract":"<div><div>In this paper, the torque, rotation, and orientation of cylindrical particles in the shear-thinning shear flow are investigated using particle-resolved direct numerical simulation. Results show that compared to Newtonian fluids, the shear-thinning properties of shear-thinning fluids significantly decrease the torque of fixed particles. For cylindrical particles rotating about a fixed axis, the shear-thinning properties significantly decrease the equilibrium orientation angle and rotational velocity of the particles. The rotational modes of particles reaching the equilibrium state can be divided into single direction rotation and damped oscillatory rotation, respectively. The increase in shear-thinning properties and the decrease in shear strength can exacerbate the damped oscillatory phenomenon. The equilibrium orientation angle and rotational velocity increase with the aspect ratio, and the former is independent of the initial orientation. The dimensionless predictive correlations of torque coefficient and equilibrium orientation angle are established within the current parameter range. The results indicate that shear-thinning properties and shear strength are crucial for particle rotation, and these findings provide guidance for predicting and controlling the rotation and orientation of the cylindrical particles.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"195 ","pages":"Article 105496"},"PeriodicalIF":3.8,"publicationDate":"2025-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145371328","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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