The two-fluid model (TFM) is foundational for modelling and simulation of dispersed-regime multiphase flows which are pervasive in natural and industrial processes. The TFM provides a coarse-grained representation of complex multiphase flows without explicitly capturing interfaces between phases through the use of volume-, time-, or ensemble-averaging. This results in the benefit of significantly reduced computational complexity but at the cost of increased approximation requiring accurate interphase transfer closures, compared to interface-capturing models. The choice of interphase transfer closures for TFM accuracy has been one of the main foci of past research, which is expansive due to the various multiphase system combinations (e.g. gas dispersed in liquid and liquid dispersed in gas). Recent research using detailed interface-capturing models has shown that the inclusion of a laminar dispersion force in the TFM when modelling bubbly flows both improves physical fidelity and mathematical completeness. In this work, a simulation-based study is performed to determine the effects of including different recently proposed laminar dispersion force models on both numerical stability and physical fidelity of a TFM formulation for gas dispersed in liquid multiphase flows. It includes a formulation of a TFM based on Brennen’s canonical formulation incorporating various recently developed laminar dispersion force closures. Overall, it is shown that inclusion of a laminar dispersion force both improves numerical stability and physical fidelity through validation with past experimental results.
{"title":"Laminar dispersion force effects on two-fluid modelling and simulation of bubble column hydrodynamics","authors":"Arshia Fazeli , Sander Rhebergen , Nasser Mohieddin Abukhdeir","doi":"10.1016/j.ijmultiphaseflow.2025.105590","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105590","url":null,"abstract":"<div><div>The two-fluid model (TFM) is foundational for modelling and simulation of dispersed-regime multiphase flows which are pervasive in natural and industrial processes. The TFM provides a coarse-grained representation of complex multiphase flows without explicitly capturing interfaces between phases through the use of volume-, time-, or ensemble-averaging. This results in the benefit of significantly reduced computational complexity but at the cost of increased approximation requiring accurate interphase transfer closures, compared to interface-capturing models. The choice of interphase transfer closures for TFM accuracy has been one of the main foci of past research, which is expansive due to the various multiphase system combinations (e.g. gas dispersed in liquid and liquid dispersed in gas). Recent research using detailed interface-capturing models has shown that the inclusion of a laminar dispersion force in the TFM when modelling bubbly flows both improves physical fidelity and mathematical completeness. In this work, a simulation-based study is performed to determine the effects of including different recently proposed laminar dispersion force models on both numerical stability and physical fidelity of a TFM formulation for gas dispersed in liquid multiphase flows. It includes a formulation of a TFM based on Brennen’s canonical formulation incorporating various recently developed laminar dispersion force closures. Overall, it is shown that inclusion of a laminar dispersion force both improves numerical stability and physical fidelity through validation with past experimental results.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"197 ","pages":"Article 105590"},"PeriodicalIF":3.8,"publicationDate":"2026-01-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145974413","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 : 2026-01-03DOI: 10.1016/j.ijmultiphaseflow.2025.105597
Jibu Tom Jose , Aviel Ben-Harosh , Omri Ram
Refractive index matching (RIM) is a powerful tool for multiphase flow studies, as it suppresses optical distortions and enables high-fidelity tomographic measurements near solid–fluid interfaces of freely moving solids. However, by improving the RIM and optical quality, the solids become effectively invisible, preventing direct identification of their location. To address this limitation, we develop a physics-informed detection framework that locates transparent spheres in time-resolved tomographic Particle Tracking Velocimetry by combining tracer density field, vertical velocity field, and vortex structures into a unified optimization problem. Integrated with volumetric reconstructions, the method provides simultaneous analysis of velocity, pressure, and force on the sphere. Applied to three acrylic spheres with diameters of 7.93, 9.53, and 11.11 mm, rising in a sodium-iodide RIM solution, the measurements capture both vortex shedding around the sphere and the evolution of the wake, showing distinct regime change between the larger sphere and the smaller ones. The smaller spheres are predominantly coupled to vortex shedding occurring close to them, while the larger sphere motion is closely related to the evolution of coherent vortices in the wake. The technique allows, for the first time, to directly calculate the drag and lift histories on a freely moving sphere over half an oscillation cycle. The framework can be extended to dynamic masking for improved tomographic reconstruction and pressure-field calculations, to non-spherical bodies with more complex motions, and to multi-body interactions, advancing RIM from a flow-only diagnostic to a tool for fully coupled body–wake measurements.
{"title":"On the application of refractive index matching to study the buoyancy-driven motion of spheres","authors":"Jibu Tom Jose , Aviel Ben-Harosh , Omri Ram","doi":"10.1016/j.ijmultiphaseflow.2025.105597","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105597","url":null,"abstract":"<div><div>Refractive index matching (RIM) is a powerful tool for multiphase flow studies, as it suppresses optical distortions and enables high-fidelity tomographic measurements near solid–fluid interfaces of freely moving solids. However, by improving the RIM and optical quality, the solids become effectively invisible, preventing direct identification of their location. To address this limitation, we develop a physics-informed detection framework that locates transparent spheres in time-resolved tomographic Particle Tracking Velocimetry by combining tracer density field, vertical velocity field, and vortex structures into a unified optimization problem. Integrated with volumetric reconstructions, the method provides simultaneous analysis of velocity, pressure, and force on the sphere. Applied to three acrylic spheres with diameters of 7.93, 9.53, and 11.11 mm, rising in a sodium-iodide RIM solution, the measurements capture both vortex shedding around the sphere and the evolution of the wake, showing distinct regime change between the larger sphere and the smaller ones. The smaller spheres are predominantly coupled to vortex shedding occurring close to them, while the larger sphere motion is closely related to the evolution of coherent vortices in the wake. The technique allows, for the first time, to directly calculate the drag and lift histories on a freely moving sphere over half an oscillation cycle. The framework can be extended to dynamic masking for improved tomographic reconstruction and pressure-field calculations, to non-spherical bodies with more complex motions, and to multi-body interactions, advancing RIM from a flow-only diagnostic to a tool for fully coupled body–wake measurements.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"197 ","pages":"Article 105597"},"PeriodicalIF":3.8,"publicationDate":"2026-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145923475","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 : 2026-01-03DOI: 10.1016/j.ijmultiphaseflow.2025.105596
T. Cheng , R. Leibovici , B. Kong , R. van Hout
Detailed measurements of the liquid jet interface dynamics close to the nozzle exit in close-coupled gas atomization focused on “filming” and “no-filming” conditions and their transitional behavior, were performed using digital inline holography. Experiments covered four Weber numbers, We, three apex angles, , for a range of momentum flux ratios, . The JPDFs of the instantaneous liquid jet interface positions revealed strikingly different interface behavior depending on the combination of We, , and . A spectral analysis identified coherent axial frequency bands, associated with the radial movement of the jet interfaces. Based on analysis of (i) reconstructed snapshots, (ii) JPDFs of instantaneous jet positions, and (iii) spectral analysis, four different “flow” regimes were proposed, namely “no-filming”, “filming”, and two transitional regimes (“periodic flapping” and intermittent “switching”). Flow regime maps (Re versus We) constructed for different apex angles, show that “filming” occurred at low Re for all investigated We. Increasing , increased the value of Re for which transitional behavior was observed. In addition, keeping constant while increasing We (implies increasing Re) may cause transition from “filming” to “no-filming”. Despite the different proposed flow regimes, peak Strouhal numbers mostly ranged between 2 St 3, irrespective of , We, and (excluding “no-filming” conditions). This study has provided a detailed spectral characterization of the transition to filming in CCGA, quantitatively expressed as regime maps that are essential for predicting primary breakup behavior and optimizing atomizer design.
{"title":"Liquid interface dynamics at primary breakup in close-coupled gas atomization","authors":"T. Cheng , R. Leibovici , B. Kong , R. van Hout","doi":"10.1016/j.ijmultiphaseflow.2025.105596","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105596","url":null,"abstract":"<div><div>Detailed measurements of the liquid jet interface dynamics close to the nozzle exit in close-coupled gas atomization focused on “filming” and “no-filming” conditions and their transitional behavior, were performed using digital inline holography. Experiments covered four Weber numbers, We<span><math><msub><mrow></mrow><mrow><mi>g</mi></mrow></msub></math></span>, three apex angles, <span><math><mi>θ</mi></math></span>, for a range of momentum flux ratios, <span><math><mi>M</mi></math></span>. The JPDFs of the instantaneous liquid jet interface positions revealed strikingly different interface behavior depending on the combination of We<span><math><msub><mrow></mrow><mrow><mi>g</mi></mrow></msub></math></span>, <span><math><mi>M</mi></math></span>, and <span><math><mi>θ</mi></math></span>. A spectral analysis identified coherent axial frequency bands, associated with the radial movement of the jet interfaces. Based on analysis of (i) reconstructed snapshots, (ii) JPDFs of instantaneous jet positions, and (iii) spectral analysis, four different “flow” regimes were proposed, namely “no-filming”, “filming”, and two transitional regimes (“periodic flapping” and intermittent “switching”). Flow regime maps (Re<span><math><msub><mrow></mrow><mrow><mi>l</mi></mrow></msub></math></span> versus We<span><math><msub><mrow></mrow><mrow><mi>g</mi></mrow></msub></math></span>) constructed for different apex angles, show that “filming” occurred at low Re<span><math><msub><mrow></mrow><mrow><mi>l</mi></mrow></msub></math></span> for all investigated We<span><math><msub><mrow></mrow><mrow><mi>g</mi></mrow></msub></math></span>. Increasing <span><math><mi>θ</mi></math></span>, increased the value of Re<span><math><msub><mrow></mrow><mrow><mi>l</mi></mrow></msub></math></span> for which transitional behavior was observed. In addition, keeping <span><math><mi>M</mi></math></span> constant while increasing We<span><math><msub><mrow></mrow><mrow><mi>g</mi></mrow></msub></math></span> (implies increasing Re<span><math><msub><mrow></mrow><mrow><mi>l</mi></mrow></msub></math></span>) may cause transition from “filming” to “no-filming”. Despite the different proposed flow regimes, peak Strouhal numbers mostly ranged between 2 <span><math><mo>≤</mo></math></span> St<span><math><mrow><msub><mrow></mrow><mrow><mi>p</mi></mrow></msub><mo>≤</mo></mrow></math></span> 3, irrespective of <span><math><mi>M</mi></math></span>, We<span><math><msub><mrow></mrow><mrow><mi>g</mi></mrow></msub></math></span>, and <span><math><mi>θ</mi></math></span> (excluding “no-filming” conditions). This study has provided a detailed spectral characterization of the transition to filming in CCGA, quantitatively expressed as regime maps that are essential for predicting primary breakup behavior and optimizing atomizer design.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"197 ","pages":"Article 105596"},"PeriodicalIF":3.8,"publicationDate":"2026-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145923476","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 : 2025-12-30DOI: 10.1016/j.ijmultiphaseflow.2025.105591
Guanzhe Cui, Adel Emadzadeh, Zhongyu Xu, Jason Monty, Jimmy Philip
<div><div>To understand the effects of particle settling and Reynolds number, experiments are conducted in a smooth-wall horizontal pipe with a diameter <span><math><mrow><mi>D</mi><mo>=</mo><mn>10</mn><mspace></mspace><mi>cm</mi></mrow></math></span>, and using particles of diameter <span><math><mrow><msub><mrow><mi>d</mi></mrow><mrow><mi>p</mi></mrow></msub><mo>=</mo><mn>250</mn><mspace></mspace><mi>μ</mi><mi>m</mi></mrow></math></span> at viscous-scale Stokes numbers of <span><math><mrow><mi>S</mi><msup><mrow><mi>t</mi></mrow><mrow><mo>+</mo></mrow></msup><mo>=</mo><mn>0</mn><mo>.</mo><mn>96</mn></mrow></math></span>–5.93, a volume fraction of <span><math><mrow><msub><mrow><mi>ϕ</mi></mrow><mrow><mi>v</mi></mrow></msub><mo>=</mo><mn>0</mn><mo>.</mo><mn>022</mn><mtext>%</mtext></mrow></math></span>, and a particle-to-fluid density ratio of <span><math><mrow><msub><mrow><mi>ρ</mi></mrow><mrow><mi>p</mi></mrow></msub><mo>/</mo><msub><mrow><mi>ρ</mi></mrow><mrow><mi>f</mi></mrow></msub><mo>=</mo><mn>1</mn><mo>.</mo><mn>05</mn></mrow></math></span>. Measurements of the streamwise and radial velocities of both the fluid and particle phases are obtained using planar imaging techniques (PIV and PTV). Two friction Reynolds numbers, <span><math><mrow><mi>R</mi><msub><mrow><mi>e</mi></mrow><mrow><mi>τ</mi></mrow></msub><mo>≈</mo><mn>850</mn></mrow></math></span> and <span><math><mrow><mn>2</mn><mspace></mspace><mn>050</mn></mrow></math></span>, corresponding to bulk Reynolds numbers of <span><math><mrow><mi>R</mi><msub><mrow><mi>e</mi></mrow><mrow><mi>b</mi></mrow></msub><mo>=</mo><mn>32</mn><mspace></mspace><mn>000</mn></mrow></math></span> and <span><math><mrow><mn>86</mn><mspace></mspace><mn>000</mn></mrow></math></span>, respectively, are studied, along with an additional experimental dataset at <span><math><mrow><mi>R</mi><msub><mrow><mi>e</mi></mrow><mrow><mi>τ</mi></mrow></msub><mo>≈</mo><mn>190</mn></mrow></math></span> with the same <span><math><mrow><msub><mrow><mi>ρ</mi></mrow><mrow><mi>p</mi></mrow></msub><mo>/</mo><msub><mrow><mi>ρ</mi></mrow><mrow><mi>f</mi></mrow></msub></mrow></math></span>. We observe that turbulence modulation depends on <span><math><mrow><mi>R</mi><msub><mrow><mi>e</mi></mrow><mrow><mi>τ</mi></mrow></msub></mrow></math></span> both at the pipe centreline and off-centreline. In general, the streamwise intensity of the fluid phase increases relative to the unladen case, the radial intensity decreases, and the Reynolds stress is reduced. The velocity statistics of the particle phase generally match those of the fluid phase, except for the radial intensity, which is higher for the particles than for the fluid, highlighting the importance of particle settling. To quantify settling due to gravity, we introduce a new non-dimensional number and use it to classify different experiments in channels and pipes. We also perform a drag decomposition, finding that at the highest <span><math><mrow><mi>R</mi><msub><mrow><mi>e</mi></mro
{"title":"Experimental study of particle-laden turbulent horizontal pipe flows up to Reτ≈ 2000 in the two-way coupling regime","authors":"Guanzhe Cui, Adel Emadzadeh, Zhongyu Xu, Jason Monty, Jimmy Philip","doi":"10.1016/j.ijmultiphaseflow.2025.105591","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105591","url":null,"abstract":"<div><div>To understand the effects of particle settling and Reynolds number, experiments are conducted in a smooth-wall horizontal pipe with a diameter <span><math><mrow><mi>D</mi><mo>=</mo><mn>10</mn><mspace></mspace><mi>cm</mi></mrow></math></span>, and using particles of diameter <span><math><mrow><msub><mrow><mi>d</mi></mrow><mrow><mi>p</mi></mrow></msub><mo>=</mo><mn>250</mn><mspace></mspace><mi>μ</mi><mi>m</mi></mrow></math></span> at viscous-scale Stokes numbers of <span><math><mrow><mi>S</mi><msup><mrow><mi>t</mi></mrow><mrow><mo>+</mo></mrow></msup><mo>=</mo><mn>0</mn><mo>.</mo><mn>96</mn></mrow></math></span>–5.93, a volume fraction of <span><math><mrow><msub><mrow><mi>ϕ</mi></mrow><mrow><mi>v</mi></mrow></msub><mo>=</mo><mn>0</mn><mo>.</mo><mn>022</mn><mtext>%</mtext></mrow></math></span>, and a particle-to-fluid density ratio of <span><math><mrow><msub><mrow><mi>ρ</mi></mrow><mrow><mi>p</mi></mrow></msub><mo>/</mo><msub><mrow><mi>ρ</mi></mrow><mrow><mi>f</mi></mrow></msub><mo>=</mo><mn>1</mn><mo>.</mo><mn>05</mn></mrow></math></span>. Measurements of the streamwise and radial velocities of both the fluid and particle phases are obtained using planar imaging techniques (PIV and PTV). Two friction Reynolds numbers, <span><math><mrow><mi>R</mi><msub><mrow><mi>e</mi></mrow><mrow><mi>τ</mi></mrow></msub><mo>≈</mo><mn>850</mn></mrow></math></span> and <span><math><mrow><mn>2</mn><mspace></mspace><mn>050</mn></mrow></math></span>, corresponding to bulk Reynolds numbers of <span><math><mrow><mi>R</mi><msub><mrow><mi>e</mi></mrow><mrow><mi>b</mi></mrow></msub><mo>=</mo><mn>32</mn><mspace></mspace><mn>000</mn></mrow></math></span> and <span><math><mrow><mn>86</mn><mspace></mspace><mn>000</mn></mrow></math></span>, respectively, are studied, along with an additional experimental dataset at <span><math><mrow><mi>R</mi><msub><mrow><mi>e</mi></mrow><mrow><mi>τ</mi></mrow></msub><mo>≈</mo><mn>190</mn></mrow></math></span> with the same <span><math><mrow><msub><mrow><mi>ρ</mi></mrow><mrow><mi>p</mi></mrow></msub><mo>/</mo><msub><mrow><mi>ρ</mi></mrow><mrow><mi>f</mi></mrow></msub></mrow></math></span>. We observe that turbulence modulation depends on <span><math><mrow><mi>R</mi><msub><mrow><mi>e</mi></mrow><mrow><mi>τ</mi></mrow></msub></mrow></math></span> both at the pipe centreline and off-centreline. In general, the streamwise intensity of the fluid phase increases relative to the unladen case, the radial intensity decreases, and the Reynolds stress is reduced. The velocity statistics of the particle phase generally match those of the fluid phase, except for the radial intensity, which is higher for the particles than for the fluid, highlighting the importance of particle settling. To quantify settling due to gravity, we introduce a new non-dimensional number and use it to classify different experiments in channels and pipes. We also perform a drag decomposition, finding that at the highest <span><math><mrow><mi>R</mi><msub><mrow><mi>e</mi></mro","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"197 ","pages":"Article 105591"},"PeriodicalIF":3.8,"publicationDate":"2025-12-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145923474","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 : 2025-12-30DOI: 10.1016/j.ijmultiphaseflow.2025.105598
Guopeng Wu , Jiacheng Sui , Zhuohang Tian , Zhijie Zhao , Guanghao Yu , Ruiying Zhang , Qiangqiang Pei , Kai Cui
This study investigates the accelerated deterioration of Damaidi rock art after summer rainfall, revealing the dry-wet degradation mechanisms of metamorphic sandstone. Based on conservation laws of mass, energy, and momentum, as well as unsaturated porous media theory, the Van Genuchten model is applied to describe water infiltration in unsaturated rock. The model accounts for solid matrix and pore fluid compressibility, thermal effects on fluid flow, and water vapor phase changes impacting rock deformation, establishing a coupled thermal-hydro-mechanical (THM) mathematical framework. Using COMSOL Multiphysics, numerical simulations of the dry-wet degradation process were conducted and validated against experimental data, including temperature, volumetric water content, and stress-strain curves. Key findings include: 1) Spatial heterogeneity in temperature and moisture fields, with boundary effects decaying with depth and a linear increase in temperature response lag; 2) Increased secondary porosity leading to a 17.8% rise in water diffusion coefficient by the 5th cycle; 3) Differential strain up to 0.12% from THM coupling, forming microcrack networks. The simulation results match experimental data with an average relative error below 8.2%, verifying the model’s accuracy in representing THM coupling behavior in unsaturated rock. These insights provide a theoretical foundation for understanding the weathering mechanisms of rock art substrates.
{"title":"Dry-Wet degradation process of unsaturated metamorphic sandstone based on multi-field coupling mechanism: A Case study of the protection of Damaidi rock art","authors":"Guopeng Wu , Jiacheng Sui , Zhuohang Tian , Zhijie Zhao , Guanghao Yu , Ruiying Zhang , Qiangqiang Pei , Kai Cui","doi":"10.1016/j.ijmultiphaseflow.2025.105598","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105598","url":null,"abstract":"<div><div>This study investigates the accelerated deterioration of Damaidi rock art after summer rainfall, revealing the dry-wet degradation mechanisms of metamorphic sandstone. Based on conservation laws of mass, energy, and momentum, as well as unsaturated porous media theory, the Van Genuchten model is applied to describe water infiltration in unsaturated rock. The model accounts for solid matrix and pore fluid compressibility, thermal effects on fluid flow, and water vapor phase changes impacting rock deformation, establishing a coupled thermal-hydro-mechanical (THM) mathematical framework. Using COMSOL Multiphysics, numerical simulations of the dry-wet degradation process were conducted and validated against experimental data, including temperature, volumetric water content, and stress-strain curves. Key findings include: 1) Spatial heterogeneity in temperature and moisture fields, with boundary effects decaying with depth and a linear increase in temperature response lag; 2) Increased secondary porosity leading to a 17.8% rise in water diffusion coefficient by the 5th cycle; 3) Differential strain up to 0.12% from THM coupling, forming microcrack networks. The simulation results match experimental data with an average relative error below 8.2%, verifying the model’s accuracy in representing THM coupling behavior in unsaturated rock. These insights provide a theoretical foundation for understanding the weathering mechanisms of rock art substrates.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"197 ","pages":"Article 105598"},"PeriodicalIF":3.8,"publicationDate":"2025-12-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145883753","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 : 2025-12-29DOI: 10.1016/j.ijmultiphaseflow.2025.105584
Michał Rajek , Jacek Pozorski
Large eddy simulations (LES) of isotropic turbulence coupled with the Lagrangian particle tracking have consistently been disregarded as a means of exploring the physics underlying turbulent dispersed two-phase flows, specifically at Reynolds numbers beyond the reach of direct numerical simulations (DNS). In the current two-part study we focus on evaluating the impact of our recently developed adaptively reconstructed spectral eddy-viscosity on the dynamics of inertial particles in LES of isotropic turbulence. To confirm the robustness of our computational framework, in the present work we first concentrate on the settling speed enhancement, clustering, and relative velocities at low Reynolds numbers. These particle statistics are of importance to determining the collision rates, influencing various environmental phenomena and industrial processes. We also indicate that the LES enriched with a well-established spectral eddy-viscosity which assumes the existence of an infinite energy spectrum is unable to reliably predict the radial distribution function and the radial relative velocities at contact. We show that the adaptively reconstructed eddy-viscosity significantly improves the predictive capabilities of LES, thus providing a tool to explore the physics underlying dispersed two-phase flows. We particularly demonstrate that under conditions relevant to cloud turbulence, certain phenomena related to particle motion can be accurately predicted without the subgrid-scale contribution to the fluid velocity at the particle location. In the companion paper we assess the ability of the proposed LES to accurately quantify particle clustering at length scales relevant to the inertial subrange at high Reynolds numbers.
{"title":"Adaptively reconstructed spectral eddy-viscosity in large eddy simulations of particle-laden isotropic turbulence, Part I: Particle statistics at low Reynolds number","authors":"Michał Rajek , Jacek Pozorski","doi":"10.1016/j.ijmultiphaseflow.2025.105584","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105584","url":null,"abstract":"<div><div>Large eddy simulations (LES) of isotropic turbulence coupled with the Lagrangian particle tracking have consistently been disregarded as a means of exploring the physics underlying turbulent dispersed two-phase flows, specifically at Reynolds numbers beyond the reach of direct numerical simulations (DNS). In the current two-part study we focus on evaluating the impact of our recently developed adaptively reconstructed spectral eddy-viscosity on the dynamics of inertial particles in LES of isotropic turbulence. To confirm the robustness of our computational framework, in the present work we first concentrate on the settling speed enhancement, clustering, and relative velocities at low Reynolds numbers. These particle statistics are of importance to determining the collision rates, influencing various environmental phenomena and industrial processes. We also indicate that the LES enriched with a well-established spectral eddy-viscosity which assumes the existence of an infinite <span><math><msup><mrow><mi>k</mi></mrow><mrow><mo>−</mo><mn>5</mn><mo>/</mo><mn>3</mn></mrow></msup></math></span> energy spectrum is unable to reliably predict the radial distribution function and the radial relative velocities at contact. We show that the adaptively reconstructed eddy-viscosity significantly improves the predictive capabilities of LES, thus providing a tool to explore the physics underlying dispersed two-phase flows. We particularly demonstrate that under conditions relevant to cloud turbulence, certain phenomena related to particle motion can be accurately predicted without the subgrid-scale contribution to the fluid velocity at the particle location. In the companion paper we assess the ability of the proposed LES to accurately quantify particle clustering at length scales relevant to the inertial subrange at high Reynolds numbers.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"197 ","pages":"Article 105584"},"PeriodicalIF":3.8,"publicationDate":"2025-12-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145923477","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 : 2025-12-26DOI: 10.1016/j.ijmultiphaseflow.2025.105595
Yuhan Li , Junhao Cai , Yunqiao Liu , Mingbo Li , Benlong Wang
The prevailing view that pits are more susceptible to cavitation nucleation than pillars has spurred extensive research on pit scenarios; however, competition among bulk, pit surface, or pillar surface nucleation under a broader range of wettability has received limited attention. Therefore, nanoscopic molecular dynamics simulations (MD) and classical nucleation theory (CNT) are employed to elucidate the competitive nucleation diagram across the three nucleation pathways. Results reveal that bulk nucleation can still out-compete surface nucleation provided the entire rough wall exhibits extreme super-wettability; however, achieving this wetting state is highly demanding. In contrast, pit-embedded surface nucleation dominates when the rough wall features uniformly weak wettability. The Blake threshold constitutes the metastable equilibrium of vapor bubbles confined within pits. Weakly wettable pillars on strongly hydrophilic substrates prevail in the competitive cavitation nucleation; however, they exert an insignificant influence when the substrate is also weakly hydrophilic, thereby allowing pit-embedded surface nucleation to dominate. The nucleation mode phase diagram establishes a universal framework for predicting the cavitation nucleation across a tailored wettability regime, offering fundamental significance to nucleation research.
{"title":"Nanoscale mapping of competitive cavitation nucleation: From surface to bulk","authors":"Yuhan Li , Junhao Cai , Yunqiao Liu , Mingbo Li , Benlong Wang","doi":"10.1016/j.ijmultiphaseflow.2025.105595","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105595","url":null,"abstract":"<div><div>The prevailing view that pits are more susceptible to cavitation nucleation than pillars has spurred extensive research on pit scenarios; however, competition among bulk, pit surface, or pillar surface nucleation under a broader range of wettability has received limited attention. Therefore, nanoscopic molecular dynamics simulations (MD) and classical nucleation theory (CNT) are employed to elucidate the competitive nucleation diagram across the three nucleation pathways. Results reveal that bulk nucleation can still out-compete surface nucleation provided the entire rough wall exhibits extreme super-wettability; however, achieving this wetting state is highly demanding. In contrast, pit-embedded surface nucleation dominates when the rough wall features uniformly weak wettability. The Blake threshold constitutes the metastable equilibrium of vapor bubbles confined within pits. Weakly wettable pillars on strongly hydrophilic substrates prevail in the competitive cavitation nucleation; however, they exert an insignificant influence when the substrate is also weakly hydrophilic, thereby allowing pit-embedded surface nucleation to dominate. The nucleation mode phase diagram establishes a universal framework for predicting the cavitation nucleation across a tailored wettability regime, offering fundamental significance to nucleation research.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"196 ","pages":"Article 105595"},"PeriodicalIF":3.8,"publicationDate":"2025-12-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145836411","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 : 2025-12-24DOI: 10.1016/j.ijmultiphaseflow.2025.105593
Zongjun Yin, Chengbin Zhang, Yongping Chen
The role of scale effects on binary nanodroplet collision dynamics is profound, as interfacial forces exhibit strong size dependence at the nanoscale. This study employs molecular dynamics simulations to investigate head-on collisions of equal-sized water nanodroplets, focusing on rupture mechanisms and interfacial dynamics at the nanoscale. The effect of disjoining pressure on nanoscale interfacial phenomena is elucidated, demonstrating a marked increase in surface energy density in thin films and nanodroplets. Four distinct outcomes are identified: regular coalescence, coalescence after perforation, limited splattering, and divergent splattering, and a regime map is constructed accordingly. The rupture instability of nanosheets formed during binary nanodroplet collisions is dictated by thermocapillary short-wave instabilities, which govern the selection of the critical wavenumber. These instabilities initiate perforation at the periphery of the spreading meniscus and subsequently propagate inward once a critical nanosheet thickness is reached. However, the relevant scaling arguments regarding the critical nanosheet thickness remain to be satisfactorily determined. Therefore, the critical nanosheet thickness is calculated semi-empirically to scale with the nanoscale critical wavelength, demonstrating that the critical thickness intriguingly becomes an invariant value for the range of Ohnesorge numbers considered. Based on the scaled critical nanosheet thickness for nanodroplet breakup, a theoretical model is developed for collision-induced breakup dynamics of binary equal-sized nanodroplets, explicitly incorporating nanoscale disjoining pressure effects. The proposed model is validated against extensive numerical simulations, and good agreement is achieved, demonstrating its predictive power for nanoscale free-flow dynamics where classical theories fail.
{"title":"Collision-induced breakup dynamics of binary equal-sized nanodroplets","authors":"Zongjun Yin, Chengbin Zhang, Yongping Chen","doi":"10.1016/j.ijmultiphaseflow.2025.105593","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105593","url":null,"abstract":"<div><div>The role of scale effects on binary nanodroplet collision dynamics is profound, as interfacial forces exhibit strong size dependence at the nanoscale. This study employs molecular dynamics simulations to investigate head-on collisions of equal-sized water nanodroplets, focusing on rupture mechanisms and interfacial dynamics at the nanoscale. The effect of disjoining pressure on nanoscale interfacial phenomena is elucidated, demonstrating a marked increase in surface energy density in thin films and nanodroplets. Four distinct outcomes are identified: regular coalescence, coalescence after perforation, limited splattering, and divergent splattering, and a regime map is constructed accordingly. The rupture instability of nanosheets formed during binary nanodroplet collisions is dictated by thermocapillary short-wave instabilities, which govern the selection of the critical wavenumber. These instabilities initiate perforation at the periphery of the spreading meniscus and subsequently propagate inward once a critical nanosheet thickness is reached. However, the relevant scaling arguments regarding the critical nanosheet thickness remain to be satisfactorily determined. Therefore, the critical nanosheet thickness is calculated semi-empirically to scale with the nanoscale critical wavelength, demonstrating that the critical thickness intriguingly becomes an invariant value for the range of Ohnesorge numbers considered. Based on the scaled critical nanosheet thickness for nanodroplet breakup, a theoretical model is developed for collision-induced breakup dynamics of binary equal-sized nanodroplets, explicitly incorporating nanoscale disjoining pressure effects. The proposed model is validated against extensive numerical simulations, and good agreement is achieved, demonstrating its predictive power for nanoscale free-flow dynamics where classical theories fail.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"196 ","pages":"Article 105593"},"PeriodicalIF":3.8,"publicationDate":"2025-12-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145880107","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}
Droplets expelled from infected hosts can deposit on surfaces and serve as fomites. Temperature‑controlled industrial equipment is also susceptible to such contamination. To test the hypothesis that substrate temperature influences droplet behaviour, we examined how temperatures from 25 °C to 70 °C affect evaporation dynamics, internal flows, deposition patterns, bacterial viability, and infectivity in Salmonella Typhimurium–laden droplets. Milli‑Q water, Luria broth (LB) medium, and meat extract were used as representative physiological fluids. Imaging and confocal microscopy techniques were used to study the evaporation dynamics and flow, whilst the morphology of dried precipitates was characterised using microscopy and profilometry. The classical “coffee-ring” deposition is exhibited at low temperatures for S. Typhimurium-Milli-Q water droplet. However, as the substrate temperature rises, thermal gradients generate strong inward Marangoni convection that competes with the capillary flow, producing thinner rings or central deposits for Milli-Q water and with dendritic structures for LB. Meanwhile, for meat extract, the patterns remained unchanged. The measured radial velocities at 50 °C were ten times higher than at 25 °C. Increased substrate temperatures resulted in a drastic reduction of the evaporation time and a decreased bacterial area of projection, keeping the bacterial aspect ratio intact. It depicted higher stress due to faster evaporation. The viability of Salmonella in precipitates was reduced with increasing substrate temperature, but infectivity remained unaltered across all base fluids.
Thus, the findings show that substrate temperature highly influences bacterial deposition and viability. The potential fomite-based infection risks from heated surfaces are outlined.
{"title":"How substrate temperature shapes Salmonella Typhimurium deposition patterns and pathogenesis in evaporating droplets","authors":"Amey Nitin Agharkar , Anmol Singh , Kush Kumar Dewangan , Dipshikha Chakravortty , Saptarshi Basu","doi":"10.1016/j.ijmultiphaseflow.2025.105592","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105592","url":null,"abstract":"<div><div>Droplets expelled from infected hosts can deposit on surfaces and serve as fomites. Temperature‑controlled industrial equipment is also susceptible to such contamination. To test the hypothesis that substrate temperature influences droplet behaviour, we examined how temperatures from 25 °C to 70 °C affect evaporation dynamics, internal flows, deposition patterns, bacterial viability, and infectivity in <em>Salmonella</em> Typhimurium–laden droplets. Milli‑Q water, Luria broth (LB) medium, and meat extract were used as representative physiological fluids. Imaging and confocal microscopy techniques were used to study the evaporation dynamics and flow, whilst the morphology of dried precipitates was characterised using microscopy and profilometry. The classical “coffee-ring” deposition is exhibited at low temperatures for <em>S.</em> Typhimurium-Milli-Q water droplet. However, as the substrate temperature rises, thermal gradients generate strong inward Marangoni convection that competes with the capillary flow, producing thinner rings or central deposits for Milli-Q water and with dendritic structures for LB. Meanwhile, for meat extract, the patterns remained unchanged. The measured radial velocities at 50 °C were ten times higher than at 25 °C. Increased substrate temperatures resulted in a drastic reduction of the evaporation time and a decreased bacterial area of projection, keeping the bacterial aspect ratio intact. It depicted higher stress due to faster evaporation. The viability of <em>Salmonella</em> in precipitates was reduced with increasing substrate temperature, but infectivity remained unaltered across all base fluids.</div><div>Thus, the findings show that substrate temperature highly influences bacterial deposition and viability. The potential fomite-based infection risks from heated surfaces are outlined.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"196 ","pages":"Article 105592"},"PeriodicalIF":3.8,"publicationDate":"2025-12-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145836918","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 : 2025-12-22DOI: 10.1016/j.ijmultiphaseflow.2025.105589
Rui Liu , Zitong Zhao , Jili Rong
Physics-informed neural networks (PINNs), which formulate loss functions based on the residuals of governing equations, have gained increasing attention for modeling fluid mechanics. However, in compressible flows, the differential form of hyperbolic conservation laws breaks down near discontinuities due to the absence of derivatives. This limitation presents a significant challenge for data-free PINN frameworks. The challenge is further intensified in multiphase flows, where contact discontinuities exhibit more complex structures and interactions, and relevant studies remain limited. To address these challenges, this study proposes a multiphase PINN model incorporating an encoder-decoder convolutional long short-term memory (ConvLSTM) deep learning framework to enable deep feature extraction and global residual computation. A multiphase Godunov-type finite volume method (FVM) loss function is developed based on a highly robust five-equation model. By employing a Godunov-type discretization derived from the weak form of the conservation laws, the framework circumvents the limits associated with strong-form discontinuities. This approach ensures entropy consistency while achieving high-resolution shock capturing in discontinuous regions. Due to the inherent dissipation of the modeling approach, the interface thickness tends to increase over time during flow evolution, which degrades the prediction accuracy of the model. To address this limitation, an improved loss function with interface anti-diffusion properties is proposed to effectively suppress interface smearing and enhance prediction fidelity. Through training and extrapolative prediction on various one-dimensional Riemann problems and high-dimensional shock cases, the proposed multiphase PINN model demonstrates accurate interface tracking and high precision in discontinuous regions. The multiphase PINN model developed in this study offers a novel predictive framework for a broad range of compressible multiphase flow problems.
{"title":"Data-Free physics-informed neural networks for modeling compressible multiphase flows","authors":"Rui Liu , Zitong Zhao , Jili Rong","doi":"10.1016/j.ijmultiphaseflow.2025.105589","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105589","url":null,"abstract":"<div><div>Physics-informed neural networks (PINNs), which formulate loss functions based on the residuals of governing equations, have gained increasing attention for modeling fluid mechanics. However, in compressible flows, the differential form of hyperbolic conservation laws breaks down near discontinuities due to the absence of derivatives. This limitation presents a significant challenge for data-free PINN frameworks. The challenge is further intensified in multiphase flows, where contact discontinuities exhibit more complex structures and interactions, and relevant studies remain limited. To address these challenges, this study proposes a multiphase PINN model incorporating an encoder-decoder convolutional long short-term memory (ConvLSTM) deep learning framework to enable deep feature extraction and global residual computation. A multiphase Godunov-type finite volume method (FVM) loss function is developed based on a highly robust five-equation model. By employing a Godunov-type discretization derived from the weak form of the conservation laws, the framework circumvents the limits associated with strong-form discontinuities. This approach ensures entropy consistency while achieving high-resolution shock capturing in discontinuous regions. Due to the inherent dissipation of the modeling approach, the interface thickness tends to increase over time during flow evolution, which degrades the prediction accuracy of the model. To address this limitation, an improved loss function with interface anti-diffusion properties is proposed to effectively suppress interface smearing and enhance prediction fidelity. Through training and extrapolative prediction on various one-dimensional Riemann problems and high-dimensional shock cases, the proposed multiphase PINN model demonstrates accurate interface tracking and high precision in discontinuous regions. The multiphase PINN model developed in this study offers a novel predictive framework for a broad range of compressible multiphase flow problems.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"196 ","pages":"Article 105589"},"PeriodicalIF":3.8,"publicationDate":"2025-12-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145836413","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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