Pub Date : 2026-01-09DOI: 10.1016/j.ijmultiphaseflow.2026.105612
Donald E. Peterson, Bradley R. Adams
This study numerically evaluated the relative contributions of drag (FD), fluid stress (FSF), added mass (FAM), and Basset history (FH) forces on particle motion as a function of particle size and gas pressure in a one-dimensional gas-solid jet. The analysis used particle and CO2 gas properties representative of a pilot-scale pressurized oxy-coal combustor inlet at 300 K. Particle diameters of 20-125 μm and gas pressures of 5-40 bar were considered with an inlet velocity of 5 m/s. Force contributions were assessed through force-to-gravity ratios and cumulative force fractions. Results showed that drag was the dominant force beyond the velocity core. However, for larger particles at elevated pressures, FSF and FH locally exceeded FD in regions where gas-particle velocity differences were small. FSF and FAM peaked at the gas velocity gradient discontinuity at the jet core exit, while FH peak lagged this location due to its history effects. FSF and FH were consistently greater than FAM at all conditions. Cumulative force contribution results confirmed that non-drag forces influenced early particle motion for 125 μm particles at 20–40 bar, though their relative importance diminished with distance. Particle velocity responsiveness to changing gas velocity increased with both size and pressure, with non-drag forces most relevant when drag was weak. Findings demonstrate that under high-pressure conditions, forces often considered negligible in atmospheric gas-solid flows may contribute significantly to local particle dynamics.
{"title":"Relative contributions of drag and non-drag forces governing particle motion in pressurized gas-solid jets","authors":"Donald E. Peterson, Bradley R. Adams","doi":"10.1016/j.ijmultiphaseflow.2026.105612","DOIUrl":"10.1016/j.ijmultiphaseflow.2026.105612","url":null,"abstract":"<div><div>This study numerically evaluated the relative contributions of drag (<em>F<sub>D</sub></em>), fluid stress (<em>F<sub>SF</sub></em>), added mass (<em>F<sub>AM</sub></em>), and Basset history (<em>F<sub>H</sub></em>) forces on particle motion as a function of particle size and gas pressure in a one-dimensional gas-solid jet. The analysis used particle and CO<sub>2</sub> gas properties representative of a pilot-scale pressurized oxy-coal combustor inlet at 300 K. Particle diameters of 20-125 μm and gas pressures of 5-40 bar were considered with an inlet velocity of 5 m/s. Force contributions were assessed through force-to-gravity ratios and cumulative force fractions. Results showed that drag was the dominant force beyond the velocity core. However, for larger particles at elevated pressures, <em>F<sub>SF</sub></em> and <em>F<sub>H</sub></em> locally exceeded <em>F<sub>D</sub></em> in regions where gas-particle velocity differences were small. <em>F<sub>SF</sub></em> and <em>F<sub>AM</sub></em> peaked at the gas velocity gradient discontinuity at the jet core exit, while <em>F<sub>H</sub></em> peak lagged this location due to its history effects. <em>F<sub>SF</sub></em> and <em>F<sub>H</sub></em> were consistently greater than <em>F<sub>AM</sub></em> at all conditions. Cumulative force contribution results confirmed that non-drag forces influenced early particle motion for 125 μm particles at 20–40 bar, though their relative importance diminished with distance. Particle velocity responsiveness to changing gas velocity increased with both size and pressure, with non-drag forces most relevant when drag was weak. Findings demonstrate that under high-pressure conditions, forces often considered negligible in atmospheric gas-solid flows may contribute significantly to local particle dynamics.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"197 ","pages":"Article 105612"},"PeriodicalIF":3.8,"publicationDate":"2026-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145974412","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 : 2026-01-08DOI: 10.1016/j.ijmultiphaseflow.2026.105609
Silvia Nauer, Joel-Steven Singh, Djamel Lakehal
In the context of the wall heat flux partitioning approach, we propose a new modelling route for high-pressure, subcooled flow boiling, which we simplify by removing the quenching part. Examining the experimental data used for comparison showed that bubble nucleation at the wall disrupts the boundary layer structure in the same way as wall roughness. We demonstrate that redefining wall friction by linking the roughness length to the bubble departure diameter produces unexpectedly good results. Only when this new model is activated can the boundary layer be correctly recovered. In addition, this work reveals that the lift force should be activated based on fundamental operating conditions such as system pressure, power, mass flux and subcooling, rather than on bubble diameter alone. The aim of this work is not to introduce a universal boiling model, but rather to highlight a few research directions that may provide greater insight into the fundamental mechanisms governing highly convective boiling flows, including the validity of lift forces in this context.
{"title":"On the modelling of the wall-void layer in high-pressure, subcooled flow boiling","authors":"Silvia Nauer, Joel-Steven Singh, Djamel Lakehal","doi":"10.1016/j.ijmultiphaseflow.2026.105609","DOIUrl":"10.1016/j.ijmultiphaseflow.2026.105609","url":null,"abstract":"<div><div>In the context of the wall heat flux partitioning approach, we propose a new modelling route for high-pressure, subcooled flow boiling, which we simplify by removing the quenching part. Examining the experimental data used for comparison showed that bubble nucleation at the wall disrupts the boundary layer structure in the same way as wall roughness. We demonstrate that redefining wall friction by linking the roughness length to the bubble departure diameter produces unexpectedly good results. Only when this new model is activated can the boundary layer be correctly recovered. In addition, this work reveals that the lift force should be activated based on fundamental operating conditions such as system pressure, power, mass flux and subcooling, rather than on bubble diameter alone. The aim of this work is not to introduce a universal boiling model, but rather to highlight a few research directions that may provide greater insight into the fundamental mechanisms governing highly convective boiling flows, including the validity of lift forces in this context.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"197 ","pages":"Article 105609"},"PeriodicalIF":3.8,"publicationDate":"2026-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145974410","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 : 2026-01-08DOI: 10.1016/j.ijmultiphaseflow.2026.105611
Dajun Xin , Jinhong Liu , Kun Xue
This study develops empirical correlations for the secondary atomization dynamics of water droplets exposed to high-speed flows spanning three orders of Weber number magnitude (We ∼ O(101)–O(103)). It achieves this by employing shock-tube experiments coupled with time-resolved shadowgraph imaging. Over 100 trials resolve the deformation and breakup processes across subsonic to supersonic regimes. Thereby, the cross-stream deformation rates, maximum flattening ratios, and dimensionless breakup initiation times (τb,i) were quantified as functions of We. The results reveal that a two-stage trend in τb,i emerges: a rapid decay below We ∼ 500 transitions to a gradual saturation above We ∼ 1500. This is consistent with a shift in breakup regime dominance from bag-type breakup to shear-induced entrainment. A novel grayscale intensity analysis method isolates the core droplet morphology from the surrounding satellite mist. This enables a precise tracking of the transient mass shedding. Core flattening persists until perimeter shear stripping initiates an exponential mass decay that follows a We-independent scaling law in the shear/ Catastrophic regime. Spatial satellite distributions (resolved via high-resolution digital in-line holography (DIH)) reveal We-dependent shedding mechanisms governed by the transition from bag-type (We ∼ O(101))to transition from bag-type to shear-driven (We ∼ O(102)) and shear-driven breakup (We ∼ O(103)). The transient drag coefficient for the core droplet depends on its aspect ratio, which evolves dynamically with shape deformation and mass shedding. Integrating these correlations for secondary atomization and time-varying drag yields trajectory predictions for core droplet that exhibit deviations less than 7% from experimental data across the tested conditions. This demonstrates the enhanced predictive accuracy of the proposed models over a broad We range.
{"title":"Experimental investigation of secondary atomization in high-speed gas flow","authors":"Dajun Xin , Jinhong Liu , Kun Xue","doi":"10.1016/j.ijmultiphaseflow.2026.105611","DOIUrl":"10.1016/j.ijmultiphaseflow.2026.105611","url":null,"abstract":"<div><div>This study develops empirical correlations for the secondary atomization dynamics of water droplets exposed to high-speed flows spanning three orders of Weber number magnitude (<em>We</em> ∼ O(10<sup>1</sup>)–O(10<sup>3</sup>)). It achieves this by employing shock-tube experiments coupled with time-resolved shadowgraph imaging. Over 100 trials resolve the deformation and breakup processes across subsonic to supersonic regimes. Thereby, the cross-stream deformation rates, maximum flattening ratios, and dimensionless breakup initiation times (<em>τ</em><sub>b,i</sub>) were quantified as functions of <em>We</em>. The results reveal that a two-stage trend in <em>τ</em><sub>b,i</sub> emerges: a rapid decay below <em>We</em> ∼ 500 transitions to a gradual saturation above <em>We</em> ∼ 1500. This is consistent with a shift in breakup regime dominance from bag-type breakup to shear-induced entrainment. A novel grayscale intensity analysis method isolates the core droplet morphology from the surrounding satellite mist. This enables a precise tracking of the transient mass shedding. Core flattening persists until perimeter shear stripping initiates an exponential mass decay that follows a <em>We</em>-independent scaling law in the shear/ Catastrophic regime. Spatial satellite distributions (resolved via high-resolution digital in-line holography (DIH)) reveal <em>We</em>-dependent shedding mechanisms governed by the transition from bag-type (<em>We</em> ∼ O(10<sup>1</sup>))to transition from bag-type to shear-driven (<em>We</em> ∼ O(10<sup>2</sup>)) and shear-driven breakup (<em>We</em> ∼ O(10<sup>3</sup>)). The transient drag coefficient for the core droplet depends on its aspect ratio, which evolves dynamically with shape deformation and mass shedding. Integrating these correlations for secondary atomization and time-varying drag yields trajectory predictions for core droplet that exhibit deviations less than 7% from experimental data across the tested conditions. This demonstrates the enhanced predictive accuracy of the proposed models over a broad <em>We</em> range.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"197 ","pages":"Article 105611"},"PeriodicalIF":3.8,"publicationDate":"2026-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146023366","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 : 2026-01-08DOI: 10.1016/j.ijmultiphaseflow.2026.105610
Abderraouf Arabi, Youssef Stiriba, Jordi Pallares
Accurately predicting flow regime transitions remains one of the key challenges in multiphase flow systems, with significant implications for design, safety, and operational reliability. In this study, novel models are introduced to predict the bubbly-to-slug flow transition in vertical downward gas–liquid flows. The transition to bubbly flow is defined in such a way that it reflects the disappearance of slug-like flow structures, offering a more intuitive physical interpretation of the underlying mechanisms. Two independent and physically meaningful criteria are proposed: (i) the onset of homogeneous flow behavior and (ii) the vanishing of the Taylor bubble. Based on these criteria, analytical expressions are derived using recent correlations for global and slug liquid holdups.
The resulting transition lines are nearly identical, underscoring the internal consistency and robustness of the proposed methodology. The models’ performances were validated against an extensive experimental database from the literature and covering a broad range of pipe diameters (9.53 mm ≤ D≤ 80 mm). They showed excellent agreement with observed transitions in most cases, confirming their predictive accuracy.
{"title":"Physically-based models for predicting the bubbly-to-slug flow transition in vertical downward gas–liquid two-phase flow","authors":"Abderraouf Arabi, Youssef Stiriba, Jordi Pallares","doi":"10.1016/j.ijmultiphaseflow.2026.105610","DOIUrl":"10.1016/j.ijmultiphaseflow.2026.105610","url":null,"abstract":"<div><div>Accurately predicting flow regime transitions remains one of the key challenges in multiphase flow systems, with significant implications for design, safety, and operational reliability. In this study, novel models are introduced to predict the bubbly-to-slug flow transition in vertical downward gas–liquid flows. The transition to bubbly flow is defined in such a way that it reflects the disappearance of slug-like flow structures, offering a more intuitive physical interpretation of the underlying mechanisms. Two independent and physically meaningful criteria are proposed: (i) the onset of homogeneous flow behavior and (ii) the vanishing of the Taylor bubble. Based on these criteria, analytical expressions are derived using recent correlations for global and slug liquid holdups.</div><div>The resulting transition lines are nearly identical, underscoring the internal consistency and robustness of the proposed methodology. The models’ performances were validated against an extensive experimental database from the literature and covering a broad range of pipe diameters (9.53 mm ≤ <em>D</em>≤ 80 mm). They showed excellent agreement with observed transitions in most cases, confirming their predictive accuracy.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"197 ","pages":"Article 105610"},"PeriodicalIF":3.8,"publicationDate":"2026-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145974415","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 : 2026-01-06DOI: 10.1016/j.ijmultiphaseflow.2026.105607
Longxiang Huang , Benjamin Duret , François-Xavier Demoulin
This study investigates the relationship between three-dimensional liquid structures and their two-dimensional projections using curvature analysis. Liquid structures are generated via a direct numerical simulation (DNS) solver for two-phase flow, and their two-dimensional projections are obtained by accumulating the Volume-of-Fluid field onto a single plane, simulating an imaging process. Curvature analysis is applied to both the three-dimensional data and the projected images across a range of Weber numbers and liquid volume fractions. Representative test cases illustrate the influence of structural superposition within this framework. Results indicate that, despite inherent projection-related biases, the curvature distributions derived from two-dimensional projections effectively capture the morphological characteristics of the original three-dimensional shapes. Key geometric features remain largely consistent across varied flow conditions. This work demonstrates the reliability of curvature-based image post-processing and outlines future pathways for integrating experimental imaging with numerical simulations under a unified curvature-analysis framework.
{"title":"Curvature analysis of the projections of the 3D liquid structures","authors":"Longxiang Huang , Benjamin Duret , François-Xavier Demoulin","doi":"10.1016/j.ijmultiphaseflow.2026.105607","DOIUrl":"10.1016/j.ijmultiphaseflow.2026.105607","url":null,"abstract":"<div><div>This study investigates the relationship between three-dimensional liquid structures and their two-dimensional projections using curvature analysis. Liquid structures are generated via a direct numerical simulation (DNS) solver for two-phase flow, and their two-dimensional projections are obtained by accumulating the Volume-of-Fluid field onto a single plane, simulating an imaging process. Curvature analysis is applied to both the three-dimensional data and the projected images across a range of Weber numbers and liquid volume fractions. Representative test cases illustrate the influence of structural superposition within this framework. Results indicate that, despite inherent projection-related biases, the curvature distributions derived from two-dimensional projections effectively capture the morphological characteristics of the original three-dimensional shapes. Key geometric features remain largely consistent across varied flow conditions. This work demonstrates the reliability of curvature-based image post-processing and outlines future pathways for integrating experimental imaging with numerical simulations under a unified curvature-analysis framework.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"197 ","pages":"Article 105607"},"PeriodicalIF":3.8,"publicationDate":"2026-01-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145974414","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 : 2026-01-06DOI: 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":"2026-01-06","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}
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}
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