Pub Date : 2026-01-20DOI: 10.1016/j.ijmultiphaseflow.2026.105627
MohammadJavad Norouzi , Jelena Andrić , Anton Vernet , Jordi Pallares , Håkan Nilsson
This study investigates flocculation in dilute suspensions of rigid fibers flowing through an asymmetric diffuser using an Eulerian–Lagrangian approach. The analysis focuses on flow-induced ballistic flocculation under varying fiber inertia and inlet (reinjection) kinematics. The fiber length exceeds the Kolmogorov length scale of the carrier flow, and finite inertia leads to a non-negligible slip velocity relative to the fluid. Large eddy simulation (LES) is applied with a dynamic subgrid-scale model to resolve the flow field and turbulence. One-way coupling between the fibers and the flow is assumed, while fiber–fiber interactions are modeled using short-range attractive forces that promote floc formation. The results show that ballistic deflection significantly accelerates flocculation in the diffuser region, establishing ballistic deflection as the dominant mechanism. In addition, inlet fiber kinematics and inertia strongly influence flocculation within the straight inflow channel.
{"title":"Large eddy simulation of fiber flocculation in a diffuser: Effects of fiber inertia and reinjection kinematics","authors":"MohammadJavad Norouzi , Jelena Andrić , Anton Vernet , Jordi Pallares , Håkan Nilsson","doi":"10.1016/j.ijmultiphaseflow.2026.105627","DOIUrl":"10.1016/j.ijmultiphaseflow.2026.105627","url":null,"abstract":"<div><div>This study investigates flocculation in dilute suspensions of rigid fibers flowing through an asymmetric diffuser using an Eulerian–Lagrangian approach. The analysis focuses on flow-induced ballistic flocculation under varying fiber inertia and inlet (reinjection) kinematics. The fiber length exceeds the Kolmogorov length scale of the carrier flow, and finite inertia leads to a non-negligible slip velocity relative to the fluid. Large eddy simulation (LES) is applied with a dynamic subgrid-scale model to resolve the flow field and turbulence. One-way coupling between the fibers and the flow is assumed, while fiber–fiber interactions are modeled using short-range attractive forces that promote floc formation. The results show that ballistic deflection significantly accelerates flocculation in the diffuser region, establishing ballistic deflection as the dominant mechanism. In addition, inlet fiber kinematics and inertia strongly influence flocculation within the straight inflow channel.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"197 ","pages":"Article 105627"},"PeriodicalIF":3.8,"publicationDate":"2026-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146074270","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 : 2026-01-19DOI: 10.1016/j.ijmultiphaseflow.2026.105624
Andrea Düll , Alexander Nies , Álvaro Echeverría de Encio , Lyes Kahouadji , Seungwon Shin , Jalel Chergui , Damir Juric , Olaf Deutschmann , Omar K. Matar
Wave evolution in thin-film flows is highly relevant for heat and mass transfer applications, such as CO2 capture in falling film absorbers. To develop a detailed understanding of potential enhancement mechanisms associated with the evolution of three-dimensional (3D) waveforms, we perform 3D direct numerical simulations of passive scalar transport in laminar-wavy film flows, using a hybrid front-tracking/level-set method to accurately resolve interfacial features. CO2 absorption is greatly enhanced in the presence of interfacial waves with the liquid-side mass transfer coefficient increasing tenfold relative to that of a flat film for the highest film Reynolds numbers () studied. This is primarily due to changes in interfacial and internal flow dynamics rather than an increase in the gas-liquid interfacial area. The recirculation region present in the leading and trailing fronts of the 3D waves intensifies mass transfer, and their effectiveness increases with . At low , there is a film region beneath the wavy interface, which remains relatively undisturbed where mass transfer is dominated by diffusion. The introduction of structured substrates to promote mass transfer under these conditions is recommended. The visco-capillary ripple region, which precedes the leading and trailing fronts for sufficiently high , provides a relatively high degree of spanwise advection, with the mean spanwise velocity magnitude reaching around one-quarter that in the streamwise direction. This underscores the importance of solving the fully-3D problem as these effects do not have a two-dimensional analogue.
{"title":"Three-dimensional effects on carbon capture in wavy falling films","authors":"Andrea Düll , Alexander Nies , Álvaro Echeverría de Encio , Lyes Kahouadji , Seungwon Shin , Jalel Chergui , Damir Juric , Olaf Deutschmann , Omar K. Matar","doi":"10.1016/j.ijmultiphaseflow.2026.105624","DOIUrl":"10.1016/j.ijmultiphaseflow.2026.105624","url":null,"abstract":"<div><div>Wave evolution in thin-film flows is highly relevant for heat and mass transfer applications, such as CO<sub>2</sub> capture in falling film absorbers. To develop a detailed understanding of potential enhancement mechanisms associated with the evolution of three-dimensional (3D) waveforms, we perform 3D direct numerical simulations of passive scalar transport in laminar-wavy film flows, using a hybrid front-tracking/level-set method to accurately resolve interfacial features. CO<sub>2</sub> absorption is greatly enhanced in the presence of interfacial waves with the liquid-side mass transfer coefficient increasing tenfold relative to that of a flat film for the highest film Reynolds numbers (<span><math><mrow><mi>R</mi><mi>e</mi></mrow></math></span>) studied. This is primarily due to changes in interfacial and internal flow dynamics rather than an increase in the gas-liquid interfacial area. The recirculation region present in the leading and trailing fronts of the 3D waves intensifies mass transfer, and their effectiveness increases with <span><math><mrow><mi>R</mi><mi>e</mi></mrow></math></span>. At low <span><math><mrow><mi>R</mi><mi>e</mi></mrow></math></span>, there is a film region beneath the wavy interface, which remains relatively undisturbed where mass transfer is dominated by diffusion. The introduction of structured substrates to promote mass transfer under these conditions is recommended. The visco-capillary ripple region, which precedes the leading and trailing fronts for sufficiently high <span><math><mrow><mi>R</mi><mi>e</mi></mrow></math></span>, provides a relatively high degree of spanwise advection, with the mean spanwise velocity magnitude reaching around one-quarter that in the streamwise direction. This underscores the importance of solving the fully-3D problem as these effects do not have a two-dimensional analogue.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"197 ","pages":"Article 105624"},"PeriodicalIF":3.8,"publicationDate":"2026-01-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146023322","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 : 2026-01-19DOI: 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":"2026-01-19","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}
Pub Date : 2026-01-16DOI: 10.1016/j.ijmultiphaseflow.2026.105620
Haifu Huang, Hervé Mutelle
This study investigates the impact of cladding ballooning on dispersed droplet flow during Loss of Coolant Accidents (LOCA), integrating experimental insights from COAL and MASCARA campaigns with advanced CFD simulations using Neptune_CFD. The work validates carrier gas flow, analyzes droplet dynamics in highly blocked subchannels, and assesses peak cladding temperature behavior under disperse droplet conditions. Handling complex balloons with a discrete forcing Immersed Boundary Methods (IBM), results highlight the critical influence of blockage ratio, blockage length, and droplet size on flow redistribution and hotspot formation. By combining detailed experiments with multiphase modeling, the study could advance understanding of coolability margins in ballooned fuel assemblies and supports the development of more predictive multiscale safety codes.
{"title":"CFD investigation of ballooning effects for dispersed droplet flow during LOCA","authors":"Haifu Huang, Hervé Mutelle","doi":"10.1016/j.ijmultiphaseflow.2026.105620","DOIUrl":"10.1016/j.ijmultiphaseflow.2026.105620","url":null,"abstract":"<div><div>This study investigates the impact of cladding ballooning on dispersed droplet flow during Loss of Coolant Accidents (LOCA), integrating experimental insights from COAL and MASCARA campaigns with advanced CFD simulations using Neptune_CFD. The work validates carrier gas flow, analyzes droplet dynamics in highly blocked subchannels, and assesses peak cladding temperature behavior under disperse droplet conditions. Handling complex balloons with a discrete forcing Immersed Boundary Methods (IBM), results highlight the critical influence of blockage ratio, blockage length, and droplet size on flow redistribution and hotspot formation. By combining detailed experiments with multiphase modeling, the study could advance understanding of coolability margins in ballooned fuel assemblies and supports the development of more predictive multiscale safety codes.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"197 ","pages":"Article 105620"},"PeriodicalIF":3.8,"publicationDate":"2026-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146023323","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 : 2026-01-14DOI: 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":"2026-01-14","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 : 2026-01-14DOI: 10.1016/j.ijmultiphaseflow.2026.105619
Guilherme Rosário dos Santos
Slug flow is a commonly encountered flow pattern in systems within the nuclear and petroleum industries. Slug length is a critical parameter for predicting pressure drop and in designing processing equipment and slug catchers. This study proposes a new correlation for slug length prediction based on an extensive experimental dataset obtained from the literature. The correlation accounts for liquid viscosity, pipe inner diameter, gas and liquid superficial velocities, gravity, gas-to-liquid density ratio, and pipe inclination. It was established using the Buckingham Pi theorem, and the resulting model was expressed in terms of Reynolds and Froude numbers, defined using liquid properties and superficial velocity, with an additional function to incorporate pipe inclination effects. When evaluated against the extensive experimental dataset across upward vertical, inclined, and horizontal pipe configurations, existing correlations performed poorly, whereas the proposed correlation demonstrated substantially improved performance. For vertical flow, 88% of 98 data points fell within a ± 30% relative error band; for inclined flow, 61–79% of 127 data points were within a ± 10% band; and for horizontal flow, 65% of 450 data points fell within a ± 30% band. Sensitivity analysis confirmed the robustness of the proposed correlation with respect to liquid viscosity and other flow parameters. The upper applicability limit of liquid viscosity was 100 mPa·s for small- and large-diameter pipes at inclinations of 90°–45° and 0°, respectively, and increased to 1000 mPa·s for nearly and fully horizontal flows.
{"title":"New correlation for slug length prediction in upward vertical, inclined, and horizontal slug flows","authors":"Guilherme Rosário dos Santos","doi":"10.1016/j.ijmultiphaseflow.2026.105619","DOIUrl":"10.1016/j.ijmultiphaseflow.2026.105619","url":null,"abstract":"<div><div>Slug flow is a commonly encountered flow pattern in systems within the nuclear and petroleum industries. Slug length is a critical parameter for predicting pressure drop and in designing processing equipment and slug catchers. This study proposes a new correlation for slug length prediction based on an extensive experimental dataset obtained from the literature. The correlation accounts for liquid viscosity, pipe inner diameter, gas and liquid superficial velocities, gravity, gas-to-liquid density ratio, and pipe inclination. It was established using the Buckingham Pi theorem, and the resulting model was expressed in terms of Reynolds and Froude numbers, defined using liquid properties and superficial velocity, with an additional function to incorporate pipe inclination effects. When evaluated against the extensive experimental dataset across upward vertical, inclined, and horizontal pipe configurations, existing correlations performed poorly, whereas the proposed correlation demonstrated substantially improved performance. For vertical flow, 88% of 98 data points fell within <em>a</em> ± 30% relative error band; for inclined flow, 61–79% of 127 data points were within <em>a</em> ± 10% band; and for horizontal flow, 65% of 450 data points fell within <em>a</em> ± 30% band. Sensitivity analysis confirmed the robustness of the proposed correlation with respect to liquid viscosity and other flow parameters. The upper applicability limit of liquid viscosity was 100 mPa·s for small- and large-diameter pipes at inclinations of 90°–45° and 0°, respectively, and increased to 1000 mPa·s for nearly and fully horizontal flows.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"197 ","pages":"Article 105619"},"PeriodicalIF":3.8,"publicationDate":"2026-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146023353","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 : 2026-01-10DOI: 10.1016/j.ijmultiphaseflow.2026.105614
Anastasia Islamova, Andrey Klimenko, Stanislav Shulyaev, Pavel Strizhak
With a variety of industrial applications involving the collisions of droplets and particles in gas, it is important to explore processes during their agglomeration and separation, as well as their classification. By recording the characteristics of droplet-particle interaction in aerosol flows, it will be possible to significantly optimize processes in abundance of systems for dust collection, liquid filtration, fine spraying, etc. The purpose of this research was to experimentally study the characteristics of interaction between water droplets and particles of coal and sand, when varying the ambient temperature from 25 to 300°С. A high-speed camera was employed to obtain shadow images of interaction of droplets and particles, with their respective velocities varying from 0.2 to 15.1 m/s and from 0.4 to 33.8 m/s. The obtained data were plotted as curves taking account of dimensionless numbers (the Weber, Reynolds, Froude and Stokes numbers). Predictive equations were derived on the basis of the experimental findings. With a temperature increase from 25°С to 300°С, the number of child droplets rose by almost 30 %. The interaction outcome was found to be mainly affected by the shape and size of solid particles, as well as their impact velocity.
{"title":"Interaction of droplets and particles in the airflow under various ambient conditions","authors":"Anastasia Islamova, Andrey Klimenko, Stanislav Shulyaev, Pavel Strizhak","doi":"10.1016/j.ijmultiphaseflow.2026.105614","DOIUrl":"10.1016/j.ijmultiphaseflow.2026.105614","url":null,"abstract":"<div><div>With a variety of industrial applications involving the collisions of droplets and particles in gas, it is important to explore processes during their agglomeration and separation, as well as their classification. By recording the characteristics of droplet-particle interaction in aerosol flows, it will be possible to significantly optimize processes in abundance of systems for dust collection, liquid filtration, fine spraying, etc. The purpose of this research was to experimentally study the characteristics of interaction between water droplets and particles of coal and sand, when varying the ambient temperature from 25 to 300°С. A high-speed camera was employed to obtain shadow images of interaction of droplets and particles, with their respective velocities varying from 0.2 to 15.1 m/s and from 0.4 to 33.8 m/s. The obtained data were plotted as curves taking account of dimensionless numbers (the Weber, Reynolds, Froude and Stokes numbers). Predictive equations were derived on the basis of the experimental findings. With a temperature increase from 25°С to 300°С, the number of child droplets rose by almost 30 %. The interaction outcome was found to be mainly affected by the shape and size of solid particles, as well as their impact velocity.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"197 ","pages":"Article 105614"},"PeriodicalIF":3.8,"publicationDate":"2026-01-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145974420","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 : 2026-01-09DOI: 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":"2026-01-09","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 : 2026-01-09DOI: 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":"2026-01-09","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 : 2026-01-09DOI: 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.
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