Pub Date : 2026-03-01Epub Date: 2026-01-09DOI: 10.1016/j.ijmultiphaseflow.2026.105615
Xiaoqiang Sun , Hong Yan , Fuzhen Chen
The multi-scale airblast atomization has important influences on the performance of modern aeroengine combustor. In the present work, the airblast atomization under high density, viscosity and velocity contrasts is investigated with a composite simulation strategy. The adaptive mesh refinement is combined with the Eulerian-Lagrangian transforming algorithm as well as breakup models to avoid unacceptable computational costs. The atomization from continuous jet to dispersed droplets is presented and analyzed. It is shown that the computational grid number of simulation without transformation is 1.52 times simulation with combined strategy under inner high-speed shearing condition. Changing shearing position presents different flow characteristics. The outer high-speed swirling gas has large space to develop and interacts with the sheet for a distance 3.6 times the inner high-speed case. Massive vortical structures are demonstrated in the shearing, turbulent and breakup regions. The Proper Orthogonal Decomposition is implemented to extract energetic coherent structures. The first four modes contribute more than 90% of the axial turbulence kinetic energy. The perturbation growth characteristics are monitored and analyzed with linear stability analysis. For the inner high-speed case, the theoretical dominant frequency is which agrees with simulation results. For the outer high-speed case, the linear stability analysis gives the trend of perturbation growth correctly. Key parameters determining the atomization performance are discussed. A comprehensive understanding of the two-phase interaction is obtained.
{"title":"Numerical simulation of airblast atomization process with transforming algorithm and breakup models","authors":"Xiaoqiang Sun , Hong Yan , Fuzhen Chen","doi":"10.1016/j.ijmultiphaseflow.2026.105615","DOIUrl":"10.1016/j.ijmultiphaseflow.2026.105615","url":null,"abstract":"<div><div>The multi-scale airblast atomization has important influences on the performance of modern aeroengine combustor. In the present work, the airblast atomization under high density, viscosity and velocity contrasts is investigated with a composite simulation strategy. The adaptive mesh refinement is combined with the Eulerian-Lagrangian transforming algorithm as well as breakup models to avoid unacceptable computational costs. The atomization from continuous jet to dispersed droplets is presented and analyzed. It is shown that the computational grid number of simulation without transformation is 1.52 times simulation with combined strategy under inner high-speed shearing condition. Changing shearing position presents different flow characteristics. The outer high-speed swirling gas has large space to develop and interacts with the sheet for a distance 3.6 times the inner high-speed case. Massive vortical structures are demonstrated in the shearing, turbulent and breakup regions. The Proper Orthogonal Decomposition is implemented to extract energetic coherent structures. The first four modes contribute more than 90% of the axial turbulence kinetic energy. The perturbation growth characteristics are monitored and analyzed with linear stability analysis. For the inner high-speed case, the theoretical dominant frequency is <span><math><mrow><mn>2546</mn><mo>.</mo><mn>5</mn><mspace></mspace><mstyle><mi>H</mi><mi>z</mi></mstyle></mrow></math></span> which agrees with simulation results. For the outer high-speed case, the linear stability analysis gives the trend of perturbation growth correctly. Key parameters determining the atomization performance are discussed. A comprehensive understanding of the two-phase interaction is obtained.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"197 ","pages":"Article 105615"},"PeriodicalIF":3.8,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145974411","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 : 2026-03-01Epub Date: 2026-01-22DOI: 10.1016/j.ijmultiphaseflow.2026.105628
Shakib Ahmed , Gretar Tryggvason , Yue Ling
The dynamics of bubbles in confined geometries is a fundamental problem with significant applications. The rise of a bubble in a wedge-shaped channel, with its opening aligned with gravity, is investigated using three-dimensional interface-resolved numerical simulations and a theoretical model. The embedded boundary and geometric volume-of-fluid methods are used to resolve the wedge wall and bubble surface, respectively. The Bond () and Laplace () numbers, along with the wedge angle, fully determine the bubble dynamics. The rising bubble reaches a stationary equilibrium state, where capillary and gravitational forces balance. The equilibrium state depends only on and the wedge angle. The theoretical model predicts that the equilibrium bubble position and height, when normalized by the capillary length, are independent of , while the normalized width increases with . Parametric simulations span a wide range of and . The Laplace number, varied by changing liquid viscosity, does not affect the equilibrium state but modulates bubble deformation during the rise.
{"title":"Rise of a confined bubble in a wedge","authors":"Shakib Ahmed , Gretar Tryggvason , Yue Ling","doi":"10.1016/j.ijmultiphaseflow.2026.105628","DOIUrl":"10.1016/j.ijmultiphaseflow.2026.105628","url":null,"abstract":"<div><div>The dynamics of bubbles in confined geometries is a fundamental problem with significant applications. The rise of a bubble in a wedge-shaped channel, with its opening aligned with gravity, is investigated using three-dimensional interface-resolved numerical simulations and a theoretical model. The embedded boundary and geometric volume-of-fluid methods are used to resolve the wedge wall and bubble surface, respectively. The Bond (<span><math><mtext>Bo</mtext></math></span>) and Laplace (<span><math><mtext>La</mtext></math></span>) numbers, along with the wedge angle, fully determine the bubble dynamics. The rising bubble reaches a stationary equilibrium state, where capillary and gravitational forces balance. The equilibrium state depends only on <span><math><mtext>Bo</mtext></math></span> and the wedge angle. The theoretical model predicts that the equilibrium bubble position and height, when normalized by the capillary length, are independent of <span><math><mtext>Bo</mtext></math></span>, while the normalized width increases with <span><math><mtext>Bo</mtext></math></span>. Parametric simulations span a wide range of <span><math><mtext>Bo</mtext></math></span> and <span><math><mtext>La</mtext></math></span>. The Laplace number, varied by changing liquid viscosity, does not affect the equilibrium state but modulates bubble deformation during the rise.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"197 ","pages":"Article 105628"},"PeriodicalIF":3.8,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146074267","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 : 2026-03-01Epub 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":"2026-03-01","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 : 2026-03-01Epub Date: 2026-01-06DOI: 10.1016/j.ijmultiphaseflow.2026.105606
Eric Thacher , Céline Gabillet , Bruno Van Ruymbeke , Simo A. Mäkiharju
Vortex induced vibration (VIV) experienced during flow past a cylinder can reduce equipment performance and in some cases lead to failure. Previous studies have shown that the shift in shedding frequency and vibration amplitude under the influence of gas injection at the upper subcritical range can produce a premature shift to supercritical flow (and the drag crisis). To date, the influence of the gas distribution along the cylinder span has not yet been investigated. Time-resolved particle image velocimetry (TR-PIV), proper orthogonal decomposition (POD) and spectral proper orthogonal decomposition (SPOD) of the wake structures, as well as bubble image velocimetry (BIV) are used to assess the flow topology changes under the influence of spanwise uniform and spanwise discontinuous gas injection. We demonstrate that for gas injected along the span of the cylinder, a premature shift to supercritical flow occurs even at volumetric qualities of 0.034%, which is lower than has been previously shown in literature. For gas injected along the central 1.3 of the channel (30% of the channel width), a local transition to supercritical flow occurs at the channel centerline; however, the wake recovers to that of subcritical flow by 3.6 downstream, as mixing occurs with the predominantly single-phase flow to either side of the bubble injection. This downstream transition in the shedding frequency resembles that of single-phase dual step cylinders, which to the author’s knowledge has not yet been shown to occur under two-phase conditions. At two-phase supercritical flow, for = 360,000, we demonstrate a significant shift in near-wake gas motion and vortex shedding frequency, with gas motion driven by vortex interaction in the separated shear layer.
{"title":"Premature transition to supercritical flow with bubbly flow around a circular cylinder","authors":"Eric Thacher , Céline Gabillet , Bruno Van Ruymbeke , Simo A. Mäkiharju","doi":"10.1016/j.ijmultiphaseflow.2026.105606","DOIUrl":"10.1016/j.ijmultiphaseflow.2026.105606","url":null,"abstract":"<div><div>Vortex induced vibration (VIV) experienced during flow past a cylinder can reduce equipment performance and in some cases lead to failure. Previous studies have shown that the shift in shedding frequency and vibration amplitude under the influence of gas injection at the upper subcritical range can produce a premature shift to supercritical flow (and the drag crisis). To date, the influence of the gas distribution along the cylinder span has not yet been investigated. Time-resolved particle image velocimetry (TR-PIV), proper orthogonal decomposition (POD) and spectral proper orthogonal decomposition (SPOD) of the wake structures, as well as bubble image velocimetry (BIV) are used to assess the flow topology changes under the influence of spanwise uniform and spanwise discontinuous gas injection. We demonstrate that for gas injected along the span of the cylinder, a premature shift to supercritical flow occurs even at volumetric qualities of 0.034%, which is lower than has been previously shown in literature. For gas injected along the central 1.3<span><math><mi>D</mi></math></span> of the channel (30% of the channel width), a local transition to supercritical flow occurs at the channel centerline; however, the wake recovers to that of subcritical flow by 3.6<span><math><mi>D</mi></math></span> downstream, as mixing occurs with the predominantly single-phase flow to either side of the bubble injection. This downstream transition in the shedding frequency resembles that of single-phase dual step cylinders, which to the author’s knowledge has not yet been shown to occur under two-phase conditions. At two-phase supercritical flow, for <span><math><mrow><mi>R</mi><msub><mrow><mi>e</mi></mrow><mrow><mi>D</mi></mrow></msub></mrow></math></span> = 360,000, we demonstrate a significant shift in near-wake gas motion and vortex shedding frequency, with gas motion driven by vortex interaction in the separated shear layer.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"197 ","pages":"Article 105606"},"PeriodicalIF":3.8,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145923422","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 : 2026-03-01Epub 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":"2026-03-01","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 : 2026-03-01Epub 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":"2026-03-01","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 : 2026-03-01Epub Date: 2026-01-09DOI: 10.1016/j.ijmultiphaseflow.2026.105608
Liping Yao , Peiyu Wang , Liangqi Zhang , Zhong Zeng , Li Li , Shouyong xie
This paper proposes a novel moving contact line model for two-phase flows containing soluble surfactants in the context of phase-field based lattice Boltzmann method (PF-LBM). The model combines a dynamic contact angle model accounting for contact line velocity with the generalized Navier boundary condition (GNBC) based on the phase-field (PF) method to capture the wetting dynamics. In this model, one LB equation solves the Navier-Stokes equations, and two others solve the two Cahn-Hilliard-like equations. A modified chemical potential is incorporated into the LBM framework, and the corresponding equilibrium distribution functions are reformulated simultaneously. First, we evaluate the reliability of the PF-LB model developed in this study by simulating a static droplet suspended in an ambient flow field and the bilateral shear problem of a single droplet. Subsequently, the proposed PF-LBM moving contact line model is extended to droplet spreading dynamics on solid surfaces. The match of the results obtained and the reference solution validates the model’s reliability. Finally, the PF-LBM moving contact line model is employed to investigate the shearing behavior of soluble surfactant-laden droplets on solid surfaces, focusing on the influences of the effective capillary number and surfactant concentration. The simulation results reveal that both the effective capillary number and the surfactant concentration significantly impact the shear wetting behavior of droplets. Holding other parameters constant, an increase in either the effective capillary number or surfactant concentration enhances the droplet deformation.
{"title":"A novel phase-field lattice Boltzmann method moving contact line model with soluble surfactants","authors":"Liping Yao , Peiyu Wang , Liangqi Zhang , Zhong Zeng , Li Li , Shouyong xie","doi":"10.1016/j.ijmultiphaseflow.2026.105608","DOIUrl":"10.1016/j.ijmultiphaseflow.2026.105608","url":null,"abstract":"<div><div>This paper proposes a novel moving contact line model for two-phase flows containing soluble surfactants in the context of phase-field based lattice Boltzmann method (PF-LBM). The model combines a dynamic contact angle model accounting for contact line velocity with the generalized Navier boundary condition (GNBC) based on the phase-field (PF) method to capture the wetting dynamics. In this model, one LB equation solves the Navier-Stokes equations, and two others solve the two Cahn-Hilliard-like equations. A modified chemical potential is incorporated into the LBM framework, and the corresponding equilibrium distribution functions are reformulated simultaneously. First, we evaluate the reliability of the PF-LB model developed in this study by simulating a static droplet suspended in an ambient flow field and the bilateral shear problem of a single droplet. Subsequently, the proposed PF-LBM moving contact line model is extended to droplet spreading dynamics on solid surfaces. The match of the results obtained and the reference solution validates the model’s reliability. Finally, the PF-LBM moving contact line model is employed to investigate the shearing behavior of soluble surfactant-laden droplets on solid surfaces, focusing on the influences of the effective capillary number and surfactant concentration. The simulation results reveal that both the effective capillary number and the surfactant concentration significantly impact the shear wetting behavior of droplets. Holding other parameters constant, an increase in either the effective capillary number or surfactant concentration enhances the droplet deformation.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"197 ","pages":"Article 105608"},"PeriodicalIF":3.8,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145974419","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 : 2026-03-01Epub Date: 2026-01-09DOI: 10.1016/j.ijmultiphaseflow.2026.105613
Ariel Sharon, Yeshayahou Levy
Cloud droplet growth is known to occur through a combination of condensation and collision-coalescence processes. While gravitational collision-coalescence becomes significant for droplets larger than approximately Φ80 μm, and condensation dominates for smaller sizes, a notable gap exists in the intermediate size range of Φ30 – Φ80 μm. In this regime, known as the "condensation-coalescence bottleneck," neither mechanism sufficiently explains the observed rapid droplet growth. To address this gap, the present experimental study investigates droplet dynamics within sprays to simulate the coalescence behavior seen in cloud environments. Focusing on the low Weber number regime, we explore water droplet interactions and growth mechanisms in the Φ5 – Φ80 μm size range, where collision-coalescence may play a crucial but is less understood. Using Vibrating Mesh Piezoelectric Atomizers (VMA) in an impinging, non-reactive spray configuration, we aim to provide new insights into the efficiency and dynamics of droplet growth, contributing to a better understanding of microphysical cloud processes.
{"title":"Collision coalescence study through the dynamics of impinging spray jets","authors":"Ariel Sharon, Yeshayahou Levy","doi":"10.1016/j.ijmultiphaseflow.2026.105613","DOIUrl":"10.1016/j.ijmultiphaseflow.2026.105613","url":null,"abstract":"<div><div>Cloud droplet growth is known to occur through a combination of condensation and collision-coalescence processes. While gravitational collision-coalescence becomes significant for droplets larger than approximately Φ80 μm, and condensation dominates for smaller sizes, a notable gap exists in the intermediate size range of Φ30 – Φ80 μm. In this regime, known as the \"condensation-coalescence bottleneck,\" neither mechanism sufficiently explains the observed rapid droplet growth. To address this gap, the present experimental study investigates droplet dynamics within sprays to simulate the coalescence behavior seen in cloud environments. Focusing on the low Weber number regime, we explore water droplet interactions and growth mechanisms in the Φ5 – Φ80 μm size range, where collision-coalescence may play a crucial but is less understood. Using Vibrating Mesh Piezoelectric Atomizers (VMA) in an impinging, non-reactive spray configuration, we aim to provide new insights into the efficiency and dynamics of droplet growth, contributing to a better understanding of microphysical cloud processes.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"197 ","pages":"Article 105613"},"PeriodicalIF":3.8,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145974418","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 : 2026-03-01Epub Date: 2026-01-14DOI: 10.1016/j.ijmultiphaseflow.2026.105618
Raphael Münster, Otto Mierka, Dmitri Kuzmin, Stefan Turek
Dense particle suspensions are promising heat transfer fluids for next-generation Concentrated Solar Power (CSP) receivers, enabling operating temperatures above 800 °C. However, accurate modeling of the rheological behavior of granular flows is essential for reliable computational fluid dynamics (CFD) simulations. In this study, we develop and assess numerical methodologies for simulating dense suspensions pertinent to CSP applications. Our computational framework is based on Direct Numerical Simulation (DNS), augmented by lubrication force models to resolve detailed particle–particle and particle–wall interactions at volume fractions exceeding 50%. We conducted a systematic series of simulations across a range of volume fractions to establish a robust reference dataset. Validation was performed via a numerical viscometer configuration, permitting direct comparison with theoretical predictions and established benchmark results. Subsequently, the viscometer arrangement was generalized to a periodic cubic domain, serving as a representative volume element for CSP systems. Within this framework, effective viscosities were quantified independently through wall force measurements and energy dissipation fitting. The close agreement between these two approaches substantiates the reliability of the results. Based on these findings, effective viscosity tables were constructed and fitted using polynomial and piecewise-smooth approximations. These high-accuracy closure relations are suitable for incorporation into large-scale, non-Newtonian CFD models for CSP plant design.
{"title":"Effective viscosity closures for dense suspensions in CSP systems via lubrication-enhanced DNS and numerical viscometry","authors":"Raphael Münster, Otto Mierka, Dmitri Kuzmin, Stefan Turek","doi":"10.1016/j.ijmultiphaseflow.2026.105618","DOIUrl":"10.1016/j.ijmultiphaseflow.2026.105618","url":null,"abstract":"<div><div>Dense particle suspensions are promising heat transfer fluids for next-generation Concentrated Solar Power (CSP) receivers, enabling operating temperatures above 800<!--> <!-->°C. However, accurate modeling of the rheological behavior of granular flows is essential for reliable computational fluid dynamics (CFD) simulations. In this study, we develop and assess numerical methodologies for simulating dense suspensions pertinent to CSP applications. Our computational framework is based on Direct Numerical Simulation (DNS), augmented by lubrication force models to resolve detailed particle–particle and particle–wall interactions at volume fractions exceeding 50%. We conducted a systematic series of simulations across a range of volume fractions to establish a robust reference dataset. Validation was performed via a numerical viscometer configuration, permitting direct comparison with theoretical predictions and established benchmark results. Subsequently, the viscometer arrangement was generalized to a periodic cubic domain, serving as a representative volume element for CSP systems. Within this framework, effective viscosities were quantified independently through wall force measurements and energy dissipation fitting. The close agreement between these two approaches substantiates the reliability of the results. Based on these findings, effective viscosity tables were constructed and fitted using polynomial and piecewise-smooth approximations. These high-accuracy closure relations are suitable for incorporation into large-scale, non-Newtonian CFD models for CSP plant design.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"197 ","pages":"Article 105618"},"PeriodicalIF":3.8,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145974416","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 : 2026-03-01Epub Date: 2026-01-19DOI: 10.1016/j.ijmultiphaseflow.2026.105621
William A. Sirignano
We analyze the unsteady heating and vaporization of a liquid droplet moving through a hot gas. Following the Abramzon–Sirignano reduced-order model, we account for a quasi-steady gas-phase boundary layer and an unsteady liquid-phase heating with the internal circulating convective transport represented through a circulation factor . The major aim is to bypass the finite-difference solution of the liquid-phase partial differential heat equation and save computational resources by developing and using a Droplet Integral Method that, through a history integral, yields the surface temperature as a function of time in the Lagrangian tracking of the droplet. Thereby, it provides sufficient information for the two-way coupling of the phases at lower cost. An approximation is introduced to facilitate the creation of a Green’s function to serve as the integral kernel; the approximation is justified by comparison with finite-difference solutions for the internal heating. The potential computational consequences for spray computations are identified and discussed. Liquid heating rate can vary significantly during droplet deceleration relative to the surrounding gas. The Stefan convection and internal liquid circulation significantly modify heating and vaporization rates. Under common constraints, although heat is continually entering at the droplet surface, vaporization rate can increase, then decrease while internal droplet circulation velocity decreases. Meanwhile, droplet radius continually decreases. For accelerating ambient gas, the relative droplet velocity can reverse direction with the droplet Reynolds number first decreasing to zero followed by later increases. In the reversing case, circulation can decrease followed by an increase.
{"title":"Integral equation for translating, vaporizing droplet","authors":"William A. Sirignano","doi":"10.1016/j.ijmultiphaseflow.2026.105621","DOIUrl":"10.1016/j.ijmultiphaseflow.2026.105621","url":null,"abstract":"<div><div>We analyze the unsteady heating and vaporization of a liquid droplet moving through a hot gas. Following the Abramzon–Sirignano reduced-order model, we account for a quasi-steady gas-phase boundary layer and an unsteady liquid-phase heating with the internal circulating convective transport represented through a circulation factor <span><math><mi>χ</mi></math></span>. The major aim is to bypass the finite-difference solution of the liquid-phase partial differential heat equation and save computational resources by developing and using a Droplet Integral Method that, through a history integral, yields the surface temperature as a function of time in the Lagrangian tracking of the droplet. Thereby, it provides sufficient information for the two-way coupling of the phases at lower cost. An approximation is introduced to facilitate the creation of a Green’s function to serve as the integral kernel; the approximation is justified by comparison with finite-difference solutions for the internal heating. The potential computational consequences for spray computations are identified and discussed. Liquid heating rate can vary significantly during droplet deceleration relative to the surrounding gas. The Stefan convection and internal liquid circulation significantly modify heating and vaporization rates. Under common constraints, although heat is continually entering at the droplet surface, vaporization rate can increase, then decrease while internal droplet circulation velocity decreases. Meanwhile, droplet radius continually decreases. For accelerating ambient gas, the relative droplet velocity can reverse direction with the droplet Reynolds number first decreasing to zero followed by later increases. In the reversing case, circulation can decrease followed by an increase.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"197 ","pages":"Article 105621"},"PeriodicalIF":3.8,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146023354","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
扫码关注我们
求助内容：
应助结果提醒方式：
京公网安备 11010802042870号