Pub Date : 2026-02-03DOI: 10.1016/j.ijmultiphaseflow.2026.105641
Junqing Lei , Guohua Wang , Xiaojing Zheng
Investigating the interaction between sand particles and an erodible bed is fundamental to understanding wind-blown sand saltation. Since natural sand beds consist of non-uniformly distributed mixed-size particles, the existing three-particle stochastic granular-bed collision model (TPSGCM) for single-size particles is insufficient. To address this, the present study has developed a mixed-size four-particle stochastic granular-bed collision model (FPSGCM) that incorporates the shielding effect. This effect is influenced by the relative size of the impacted and shielding particles, as well as their relative vertical position. The new FPSGCM accurately reproduces the splash process of mixed-size particles. When applied to simulate wind-blown sand flow, the model predictions for the sand transport rate, saltation length, and height are in better agreement with experimental and theoretical results.
{"title":"A mechanical model for the mixed-size particle splash process based on the stochastic particle-bed collision","authors":"Junqing Lei , Guohua Wang , Xiaojing Zheng","doi":"10.1016/j.ijmultiphaseflow.2026.105641","DOIUrl":"10.1016/j.ijmultiphaseflow.2026.105641","url":null,"abstract":"<div><div>Investigating the interaction between sand particles and an erodible bed is fundamental to understanding wind-blown sand saltation. Since natural sand beds consist of non-uniformly distributed mixed-size particles, the existing three-particle stochastic granular-bed collision model (TPSGCM) for single-size particles is insufficient. To address this, the present study has developed a mixed-size four-particle stochastic granular-bed collision model (FPSGCM) that incorporates the shielding effect. This effect is influenced by the relative size of the impacted and shielding particles, as well as their relative vertical position. The new FPSGCM accurately reproduces the splash process of mixed-size particles. When applied to simulate wind-blown sand flow, the model predictions for the sand transport rate, saltation length, and height are in better agreement with experimental and theoretical results.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"198 ","pages":"Article 105641"},"PeriodicalIF":3.8,"publicationDate":"2026-02-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146116565","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 : 2026-01-31DOI: 10.1016/j.ijmultiphaseflow.2026.105637
Xiaofei Hu , Bing Zhu , Mingyang Lv , Wei Zhang
Droplet impact on conical surfaces is relevant to both natural processes and industrial applications. This study examines the interfacial evolution of droplets impacting superhydrophobic cones through experiments, simulations, and theoretical analysis, focusing on the effects of Weber number and cone angle. Four distinct impact modes are identified: (I) complete rebound without penetration; (II) penetration with ring formation and complete rebound; (III) penetration with ring formation followed by breakup during retraction; and (IV) penetration with ring formation followed by breakup during spreading. Increasing Weber number enhances the maximum spreading factor and prolongs spreading time, while larger cone angles suppress spreading and reduce the corresponding time. For non-penetration cases (Mode I), a pancake-like theoretical model based on energy conservation accurately predicts the maximum spreading factor. Mechanistically, Modes I–II arise from the balance of inertia and surface tension, Mode III from Rayleigh–Plateau instability, and Mode IV from local necking-induced ring rupture.
{"title":"Mechanisms of Interfacial Evolution in Droplet Impact on Superhydrophobic Cones","authors":"Xiaofei Hu , Bing Zhu , Mingyang Lv , Wei Zhang","doi":"10.1016/j.ijmultiphaseflow.2026.105637","DOIUrl":"10.1016/j.ijmultiphaseflow.2026.105637","url":null,"abstract":"<div><div>Droplet impact on conical surfaces is relevant to both natural processes and industrial applications. This study examines the interfacial evolution of droplets impacting superhydrophobic cones through experiments, simulations, and theoretical analysis, focusing on the effects of Weber number and cone angle. Four distinct impact modes are identified: (I) complete rebound without penetration; (II) penetration with ring formation and complete rebound; (III) penetration with ring formation followed by breakup during retraction; and (IV) penetration with ring formation followed by breakup during spreading. Increasing Weber number enhances the maximum spreading factor and prolongs spreading time, while larger cone angles suppress spreading and reduce the corresponding time. For non-penetration cases (Mode I), a pancake-like theoretical model based on energy conservation accurately predicts the maximum spreading factor. Mechanistically, Modes I–II arise from the balance of inertia and surface tension, Mode III from Rayleigh–Plateau instability, and Mode IV from local necking-induced ring rupture.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"198 ","pages":"Article 105637"},"PeriodicalIF":3.8,"publicationDate":"2026-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146116564","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 : 2026-01-29DOI: 10.1016/j.ijmultiphaseflow.2026.105635
Mariana Costa , Tom van Terwisga , Daniele Fiscaletti , Jerry Westerweel
In tribonucleation, a liquid-to-gas phase transition induced by a local pressure drop (cavitation) is highly undesirable, as it causes surface erosion and noise. A paradigmatic flow characteristic of tribonucleation problems is the flow between two coaxial disks. The flow is produced by the rapid upward movement of the top disk, which is initially at rest and in contact with the bottom disk. An analytical model, the so-called negative squeeze film, is typically used to predict the flow in the gap between the disks in this class of problems. Such a model considers an azimuthally uniform inflow in the gap between the disks. In this study, we experimentally show that if a negligibly small misalignment between the axes of the two disks is introduced, the inflow is not azimuthally uniform as expected from the negative squeeze film, but an entry jet appears in the flow between the disks. This entry jet is associated with the formation of two counter-rotating vortices. From reconstructing the pressure field from PIV velocity data in the vortex regions, we find that the local pressure is lower than the vapor pressure. This indicates that the gaseous phase in the cores of the vortices, which is observed from shadowgraphy visualizations in our study, should be attributed to cavitation. The negative-squeeze-film model, however, largely fails to predict the minimum pressure. Therefore, the onset of cavitation is not correctly captured by the analytical model.
{"title":"Cavitation onset in counter-rotating vortices from separating disks","authors":"Mariana Costa , Tom van Terwisga , Daniele Fiscaletti , Jerry Westerweel","doi":"10.1016/j.ijmultiphaseflow.2026.105635","DOIUrl":"10.1016/j.ijmultiphaseflow.2026.105635","url":null,"abstract":"<div><div>In tribonucleation, a liquid-to-gas phase transition induced by a local pressure drop (cavitation) is highly undesirable, as it causes surface erosion and noise. A paradigmatic flow characteristic of tribonucleation problems is the flow between two coaxial disks. The flow is produced by the rapid upward movement of the top disk, which is initially at rest and in contact with the bottom disk. An analytical model, the so-called negative squeeze film, is typically used to predict the flow in the gap between the disks in this class of problems. Such a model considers an azimuthally uniform inflow in the gap between the disks. In this study, we experimentally show that if a negligibly small misalignment between the axes of the two disks is introduced, the inflow is not azimuthally uniform as expected from the negative squeeze film, but an entry jet appears in the flow between the disks. This entry jet is associated with the formation of two counter-rotating vortices. From reconstructing the pressure field from PIV velocity data in the vortex regions, we find that the local pressure is lower than the vapor pressure. This indicates that the gaseous phase in the cores of the vortices, which is observed from shadowgraphy visualizations in our study, should be attributed to cavitation. The negative-squeeze-film model, however, largely fails to predict the minimum pressure. Therefore, the onset of cavitation is not correctly captured by the analytical model.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"197 ","pages":"Article 105635"},"PeriodicalIF":3.8,"publicationDate":"2026-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146074278","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 : 2026-01-29DOI: 10.1016/j.ijmultiphaseflow.2026.105625
L. Rosenberg , W.D. Fullmer , S. Beetham
The computational study of strongly-coupled, gas–solid flows at scales relevant to most environmental and engineering applications requires the use of ‘coarse-grained’ methodologies such as the two-fluid model, particle-in-cell approach or the multiphase Reynolds Averaged Navier–Stokes equations. While these strategies enable computations at desirable length- and time-scales, they rely heavily on models to capture important flow physics that occur at scales smaller than the mesh. To date, the models that do exist are based on a limited set of flow conditions, such as very dilute particle phase. To this end, we leverage a large-scale repository of CFD-DEM data to develop filter-size dependent models for the mean variance in particle volume fraction, a quantity commonly used to assess the degree of clustering, and the granular temperature, a key quantity for accurately predicting gas–solid flows. Because of its filter-size dependence, the granular temperature model can be directly translated to coarse-grained approaches and tied directly to grid size.
{"title":"A filter-dependent granular temperature model from large-scale CFD-DEM data","authors":"L. Rosenberg , W.D. Fullmer , S. Beetham","doi":"10.1016/j.ijmultiphaseflow.2026.105625","DOIUrl":"10.1016/j.ijmultiphaseflow.2026.105625","url":null,"abstract":"<div><div>The computational study of strongly-coupled, gas–solid flows at scales relevant to most environmental and engineering applications requires the use of ‘coarse-grained’ methodologies such as the two-fluid model, particle-in-cell approach or the multiphase Reynolds Averaged Navier–Stokes equations. While these strategies enable computations at desirable length- and time-scales, they rely heavily on models to capture important flow physics that occur at scales smaller than the mesh. To date, the models that do exist are based on a limited set of flow conditions, such as very dilute particle phase. To this end, we leverage a large-scale repository of CFD-DEM data to develop filter-size dependent models for the mean variance in particle volume fraction, a quantity commonly used to assess the degree of clustering, and the granular temperature, a key quantity for accurately predicting gas–solid flows. Because of its filter-size dependence, the granular temperature model can be directly translated to coarse-grained approaches and tied directly to grid size.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"197 ","pages":"Article 105625"},"PeriodicalIF":3.8,"publicationDate":"2026-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146074268","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 : 2026-01-28DOI: 10.1016/j.ijmultiphaseflow.2026.105634
Abdullah M. Abdal , Debashis Panda , Lyes Kahouadji , Mosayeb Shams , Seungwon Shin , Jalel Chergui , Damir Juric , Omar K. Matar
We perform three-dimensional simulations of miscible and immiscible displacements in a cylindrical pipe. For the miscible case, both laminar and turbulent displacement regimes are considered, and our numerical framework uses direct numerical simulation (DNS) and a Large Eddy Simulation (LES) approach based on a Lilly–Smagorinsky model. The dynamics of the flow are governed by the Navier–Stokes equations, coupled with a convective-diffusion equation for the concentration of the more viscous fluid when considering the miscible cases. For the immiscible laminar cases, we perform two-phase DNS considering both pinned and moving contact lines to capture the full range of immiscible dynamic behaviours. The pinned contact line reflects stationary interfaces constrained by surface heterogeneity, while the moving contact line accounts for dynamic interfacial motion influenced by viscous and capillary forces. This study shows that the viscosity contrasts between the two fluids play a significant role in determining the efficiency of ‘cleaning’ of a pipe containing an initially highly viscous resident fluid. When the viscosity of the displaced fluid is low, the laminar displacement flow is efficient in cleaning the pipe; however, when the viscosity increases, the laminar displacement becomes inadequate. Our numerical predictions in the turbulent regime showed that more efficient cleaning is achieved when the viscosity contrast between the two fluids is large. Lastly, our results reveal that the dynamics of a moving contact line can impact both the efficiency and the pattern of cleaning within the pipe.
{"title":"Three-dimensional numerical simulations of product changeover: Miscible and immiscible displacements in circular tubes","authors":"Abdullah M. Abdal , Debashis Panda , Lyes Kahouadji , Mosayeb Shams , Seungwon Shin , Jalel Chergui , Damir Juric , Omar K. Matar","doi":"10.1016/j.ijmultiphaseflow.2026.105634","DOIUrl":"10.1016/j.ijmultiphaseflow.2026.105634","url":null,"abstract":"<div><div>We perform three-dimensional simulations of miscible and immiscible displacements in a cylindrical pipe. For the miscible case, both laminar and turbulent displacement regimes are considered, and our numerical framework uses direct numerical simulation (DNS) and a Large Eddy Simulation (LES) approach based on a Lilly–Smagorinsky model. The dynamics of the flow are governed by the Navier–Stokes equations, coupled with a convective-diffusion equation for the concentration of the more viscous fluid when considering the miscible cases. For the immiscible laminar cases, we perform two-phase DNS considering both pinned and moving contact lines to capture the full range of immiscible dynamic behaviours. The pinned contact line reflects stationary interfaces constrained by surface heterogeneity, while the moving contact line accounts for dynamic interfacial motion influenced by viscous and capillary forces. This study shows that the viscosity contrasts between the two fluids play a significant role in determining the efficiency of ‘cleaning’ of a pipe containing an initially highly viscous resident fluid. When the viscosity of the displaced fluid is low, the laminar displacement flow is efficient in cleaning the pipe; however, when the viscosity increases, the laminar displacement becomes inadequate. Our numerical predictions in the turbulent regime showed that more efficient cleaning is achieved when the viscosity contrast between the two fluids is large. Lastly, our results reveal that the dynamics of a moving contact line can impact both the efficiency and the pattern of cleaning within the pipe.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"197 ","pages":"Article 105634"},"PeriodicalIF":3.8,"publicationDate":"2026-01-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146074275","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}
Heat transfer in porous fiber-reinforced composite cylinders is critical for enhancing thermal system performance in applications such as material drying, atomization devices, and aerospace engineering. However, the influence of compressible fluid flow within porous structures remains insufficiently understood due to limited experimental data and incomplete theoretical models. This study establishes a transient heat and mass transfer model for a multilayer porous composite cylinder containing hygroscopic moisture. The model incorporates Darcy-based flow and local thermal non-equilibrium (LTNE) assumptions. It accounts for critical water saturation, gravitational effects, and gas compressibility. Solved using the finite volume method, the model predicts unsteady thermal and mass transport behavior. Its accuracy is validated via a custom experimental platform. Finally, the effects of thermal conductivity, porosity, and moisture saturation on heat and mass transfer characteristics are analyzed. The proposed model provides a reliable tool for predicting transient thermal behavior in porous composite systems, offering concrete guidance for the design and performance optimization of advanced thermal equipment such as insulation sleeves, drying cylinders, and thermal storage components.
{"title":"Unsteady heat and mass transfer in composite cylinders with water-containing hygroscopic porous media and compressible gas phase","authors":"Yu-Cheng Wei , Zheng-Wei Huang , Hong-Liang Dai, Zhi-Wei Sun, Jian Xu","doi":"10.1016/j.ijmultiphaseflow.2026.105632","DOIUrl":"10.1016/j.ijmultiphaseflow.2026.105632","url":null,"abstract":"<div><div>Heat transfer in porous fiber-reinforced composite cylinders is critical for enhancing thermal system performance in applications such as material drying, atomization devices, and aerospace engineering. However, the influence of compressible fluid flow within porous structures remains insufficiently understood due to limited experimental data and incomplete theoretical models. This study establishes a transient heat and mass transfer model for a multilayer porous composite cylinder containing hygroscopic moisture. The model incorporates Darcy-based flow and local thermal non-equilibrium (LTNE) assumptions. It accounts for critical water saturation, gravitational effects, and gas compressibility. Solved using the finite volume method, the model predicts unsteady thermal and mass transport behavior. Its accuracy is validated via a custom experimental platform. Finally, the effects of thermal conductivity, porosity, and moisture saturation on heat and mass transfer characteristics are analyzed. The proposed model provides a reliable tool for predicting transient thermal behavior in porous composite systems, offering concrete guidance for the design and performance optimization of advanced thermal equipment such as insulation sleeves, drying cylinders, and thermal storage components.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"197 ","pages":"Article 105632"},"PeriodicalIF":3.8,"publicationDate":"2026-01-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146074269","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 effect of viscoelasticity on drop deformation in the presence of an electric field is investigated using both analytical and numerical methods. The study focuses on two configurations, namely, a viscoelastic drop suspended in a Newtonian fluid and a Newtonian drop suspended in a viscoelastic medium. Oldroyd-B constitutive equation is employed to model the constant viscosity viscoelasticity. Effect of Deborah number (ratio of polymer relaxation time to convective time scale) on drop deformation is studied by examining the electric, elastic and viscous stresses at the interface. For small deformations, we apply the method of domain perturbations, and show that the viscoelastic properties of the drop significantly influence its deformation more than when the surrounding fluid is viscoelastic. Numerical computations are performed using a finite volume framework for larger drop deformations. The transient dynamics of the drops show distinct oscillatory patterns before eventually stabilizing at a steady deformation value. We observe a trend of decreased deformation in both configurations as the Deborah number increases. Relative magnitude of normal and tangential stresses plays a crucial role in drop deformation.
{"title":"Effect of viscoelasticity on electrohydrodynamic drop deformation","authors":"Santanu Kumar Das , Sarika Shivaji Bangar , Amaresh Dalal , Gaurav Tomar","doi":"10.1016/j.ijmultiphaseflow.2026.105633","DOIUrl":"10.1016/j.ijmultiphaseflow.2026.105633","url":null,"abstract":"<div><div>The effect of viscoelasticity on drop deformation in the presence of an electric field is investigated using both analytical and numerical methods. The study focuses on two configurations, namely, a viscoelastic drop suspended in a Newtonian fluid and a Newtonian drop suspended in a viscoelastic medium. Oldroyd-B constitutive equation is employed to model the constant viscosity viscoelasticity. Effect of Deborah number (ratio of polymer relaxation time to convective time scale) on drop deformation is studied by examining the electric, elastic and viscous stresses at the interface. For small deformations, we apply the method of domain perturbations, and show that the viscoelastic properties of the drop significantly influence its deformation more than when the surrounding fluid is viscoelastic. Numerical computations are performed using a finite volume framework for larger drop deformations. The transient dynamics of the drops show distinct oscillatory patterns before eventually stabilizing at a steady deformation value. We observe a trend of decreased deformation in both configurations as the Deborah number increases. Relative magnitude of normal and tangential stresses plays a crucial role in drop deformation.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"197 ","pages":"Article 105633"},"PeriodicalIF":3.8,"publicationDate":"2026-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146074277","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 : 2026-01-24DOI: 10.1016/j.ijmultiphaseflow.2026.105631
A. Madhav Sai Kumar , A. Hari Govindha , Ranajit Mondal , Kirti Chandra Sahu
The drying of colloidal suspensions leads to complex deposition patterns, accompanied by instabilities such as cracking and delamination. In this study, we experimentally investigate the coupled influence of particle surface charge and substrate wettability on the evaporation dynamics, final deposition morphology, and crack patterns of sessile droplets containing silica nanoparticles. We examine the dynamics of two types of colloids, namely the negatively charged colloidal silica nanoparticles (Ludox TM50) and the positively charged silica nanoparticle (Ludox CL30), at concentrations ranging from 0.1 wt% to 5.0 wt%, deposited on glass, polystyrene, and polytetrafluoroethylene (PTFE) substrates with distinct wettability. Side and top-view imaging techniques are employed to capture the evaporation process and analyze the resulting cracks. Our results reveal that the nature of the particle charge and substrate wettability significantly affect the evaporation mode, with transitions observed between constant contact radius (CCR), constant contact angle (CCA), and mixed modes. TM50-laden droplets consistently exhibit radial cracks, whereas CL30 droplets display more randomly oriented and irregular cracks. At higher particle concentrations, TM50 suspensions form thicker deposits that undergo delamination, particularly on highly wettable substrates like glass. Quantitative analysis reveals that crack spacing and length follow power-law relationships with particle concentration. Additionally, the delamination behavior is strongly influenced by both the particle concentration and the type of substrate. We propose a mechanistic framework to explain the role of particle–substrate interactions in governing the observed cracking and delamination behaviors.
{"title":"Instabilities in drying colloidal films: Role of surface charge and substrate wettability","authors":"A. Madhav Sai Kumar , A. Hari Govindha , Ranajit Mondal , Kirti Chandra Sahu","doi":"10.1016/j.ijmultiphaseflow.2026.105631","DOIUrl":"10.1016/j.ijmultiphaseflow.2026.105631","url":null,"abstract":"<div><div>The drying of colloidal suspensions leads to complex deposition patterns, accompanied by instabilities such as cracking and delamination. In this study, we experimentally investigate the coupled influence of particle surface charge and substrate wettability on the evaporation dynamics, final deposition morphology, and crack patterns of sessile droplets containing silica nanoparticles. We examine the dynamics of two types of colloids, namely the negatively charged colloidal silica nanoparticles (Ludox TM50) and the positively charged silica nanoparticle (Ludox CL30), at concentrations ranging from 0.1 wt% to 5.0 wt%, deposited on glass, polystyrene, and polytetrafluoroethylene (PTFE) substrates with distinct wettability. Side and top-view imaging techniques are employed to capture the evaporation process and analyze the resulting cracks. Our results reveal that the nature of the particle charge and substrate wettability significantly affect the evaporation mode, with transitions observed between constant contact radius (CCR), constant contact angle (CCA), and mixed modes. TM50-laden droplets consistently exhibit radial cracks, whereas CL30 droplets display more randomly oriented and irregular cracks. At higher particle concentrations, TM50 suspensions form thicker deposits that undergo delamination, particularly on highly wettable substrates like glass. Quantitative analysis reveals that crack spacing and length follow power-law relationships with particle concentration. Additionally, the delamination behavior is strongly influenced by both the particle concentration and the type of substrate. We propose a mechanistic framework to explain the role of particle–substrate interactions in governing the observed cracking and delamination behaviors.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"197 ","pages":"Article 105631"},"PeriodicalIF":3.8,"publicationDate":"2026-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146074276","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 : 2026-01-22DOI: 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":"2026-01-22","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 : 2026-01-20DOI: 10.1016/j.ijmultiphaseflow.2026.105623
Peddi Harishteja , Deekshith I. Poojary , Cristian Marchioli , Vagesh D. Narasimhamurthy
In this study, we examine the effect produced by different inflow conditions on the behavior of inertial particles within the wake produced by a normal flat plate. To this aim, we perform Euler–Lagrangian simulations of the particle-laden wake, using the in-house solver MGLET-LaParT. An unsteady wake with a Reynolds number of 60 is considered, and four inflow conditions are examined: uniform inflow, planar shear inflow, and addition of inflow turbulence to both uniform and planar shear. Particles with different Stokes numbers (, and 10) are analyzed. Particle dispersion, voids, and connected clusters are quantified using Voronoï tessellations and Minkowski functionals, along with statistics of concentration, particle velocity, and slip velocity. The results reveal a distinct influence of both inertia and inflow conditions. Uniform inflow produces symmetric lateral accumulation, whereas planar shear induces asymmetry and enhances wake centerline concentration. With the addition of inflow turbulence to planar shear, the particles at the periphery of the voids created by vortices become more dispersed and irregular, particularly at the highest Stokes number (). Cluster formation is analyzed by backtracking the particles that eventually form clusters. Further analysis indicates that cluster morphology depends on particle inertia: Elongated clusters are found at , the largest compact clusters at , and diffuse clusters at . Inflow conditions modulate cluster coherence, particularly at higher Stokes numbers. The probability distributions of normalized cluster areas exhibit power-law decay, highlighting fractal, scale-free organization dominated by intermediate-sized clusters. We believe these findings provide a quantitative framework linking inflow, inertia, and wake dynamics, offering benchmarks for predictive multiphase flow models.
{"title":"On the particle clustering in the wake of a normal flat plate: Influence of inflow boundary conditions","authors":"Peddi Harishteja , Deekshith I. Poojary , Cristian Marchioli , Vagesh D. Narasimhamurthy","doi":"10.1016/j.ijmultiphaseflow.2026.105623","DOIUrl":"10.1016/j.ijmultiphaseflow.2026.105623","url":null,"abstract":"<div><div>In this study, we examine the effect produced by different inflow conditions on the behavior of inertial particles within the wake produced by a normal flat plate. To this aim, we perform Euler–Lagrangian simulations of the particle-laden wake, using the in-house solver MGLET-LaParT. An unsteady wake with a Reynolds number of 60 is considered, and four inflow conditions are examined: uniform inflow, planar shear inflow, and addition of inflow turbulence to both uniform and planar shear. Particles with different Stokes numbers (<span><math><mrow><mi>S</mi><mi>t</mi><mo>=</mo><mn>0</mn><mo>.</mo><mn>1</mn><mo>,</mo><mn>1</mn><mo>,</mo><mn>5</mn></mrow></math></span>, and 10) are analyzed. Particle dispersion, voids, and connected clusters are quantified using Voronoï tessellations and Minkowski functionals, along with statistics of concentration, particle velocity, and slip velocity. The results reveal a distinct influence of both inertia and inflow conditions. Uniform inflow produces symmetric lateral accumulation, whereas planar shear induces asymmetry and enhances wake centerline concentration. With the addition of inflow turbulence to planar shear, the particles at the periphery of the voids created by vortices become more dispersed and irregular, particularly at the highest Stokes number (<span><math><mrow><mi>S</mi><mi>t</mi><mo>=</mo><mn>10</mn></mrow></math></span>). Cluster formation is analyzed by backtracking the particles that eventually form clusters. Further analysis indicates that cluster morphology depends on particle inertia: Elongated clusters are found at <span><math><mrow><mi>S</mi><mi>t</mi><mo>=</mo><mn>1</mn></mrow></math></span>, the largest compact clusters at <span><math><mrow><mi>S</mi><mi>t</mi><mo>=</mo><mn>5</mn></mrow></math></span>, and diffuse clusters at <span><math><mrow><mi>S</mi><mi>t</mi><mo>=</mo><mn>10</mn></mrow></math></span>. Inflow conditions modulate cluster coherence, particularly at higher Stokes numbers. The probability distributions of normalized cluster areas exhibit power-law decay, highlighting fractal, scale-free organization dominated by intermediate-sized clusters. We believe these findings provide a quantitative framework linking inflow, inertia, and wake dynamics, offering benchmarks for predictive multiphase flow models.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"197 ","pages":"Article 105623"},"PeriodicalIF":3.8,"publicationDate":"2026-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146074274","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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