International Journal of Multiphase Flow最新文献

{"title":"Modal analysis reveals imprint of snowflake shape on wake flow structures","authors":"Giorgia Tagliavini ,&nbsp;Markus Holzner ,&nbsp;Pascal Corso","doi":"10.1016/j.ijmultiphaseflow.2025.105365","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105365","url":null,"abstract":"<div><div>This study investigates the complex interplay of wake flow dynamics, particle shape, and falling behavior of snowflakes through advanced flow analysis. We employ Proper Orthogonal Decomposition and Dynamic Mode Decomposition to analyze the wake flow patterns of three distinct snowflake geometries at a Reynolds number of 1500: a dendrite crystal, a columnar crystal, and a rosette-like particle. Proper Orthogonal Decomposition reveals that spatial resolution significantly impacts the capture of flow structures, particularly for particles with more intricate wake flow structure, corresponding to unstable falling motion. Dynamic Mode Decomposition demonstrates high sensitivity to temporal resolution, with data of the forces exerted on the snowflake incorporated in the matrix prior to the decomposition mitigating information loss at lower sampling rates. We establish a linear relationship between snowflake shape porosity and minimum and maximum Dynamic Mode Decomposition eigenfrequencies, absolute decay or growth rates, and the wavenumber of the most energetic mode, linking particle geometry to wake flow characteristics. Higher porosity corresponds to more stable, small-scale flow structures and steady falling motion, while lower porosity promotes larger, unstable structures and falling trajectories with random particle orientations. These findings reveal the interdependence of snowflake geometry, wake flow dynamics, and falling behavior and highlight the importance of considering both spatial and temporal resolutions when dealing with modal analysis. This research contributes to improved predictions of snowflake falling behavior, with potential applications in meteorology and climate science.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"193 ","pages":"Article 105365"},"PeriodicalIF":3.6,"publicationDate":"2025-07-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144713511","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}

{"title":"Experimental investigation on characteristics of flow-induced acoustics in horizontal gas–liquid two-phase flow","authors":"Nannan Zhao,&nbsp;Guojun Zhu,&nbsp;Jianjun Feng,&nbsp;Xingqi Luo,&nbsp;Jingyue Song","doi":"10.1016/j.ijmultiphaseflow.2025.105378","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105378","url":null,"abstract":"<div><div>The dynamic behavior of bubbles and their interactions with fluid walls in bubble-laden liquid flows inevitably generate outwardly propagating sound waves, which are crucial for monitoring pipeline stability. However, the influence of flow patterns on gas–liquid two-phase flow-induced sound (GTFIS) emissions, especially under high Reynolds numbers, remains inadequately understood. In this study, GTFIS signals under high Reynolds numbers in a horizontal pipe were captured using a precision hydrophone. The results reveal that the energy of GTFIS signals is predominantly concentrated within 0–50 Hz. Among all flow patterns in conventional horizontal pipes, slug flow (SG) exhibits the highest GTFIS signal intensity. The signal intensity in SG increases linearly with gas velocity due to the combined effects of rising bubble-induced turbulence effect and slug frequency. In intermittent flow, the GTFIS signal exhibits increased non-Gaussianity and approximately follows a stable distribution. The structural complexity and multifractality of GTFIS signals are governed by bubble behavior and flow pattern transitions. Furthermore, in intermittent flow, the multifractal strength is maximized due to the enhanced intermittency of the internal flow and the inhomogeneous two-phase distribution. The parameters of the multifractal spectrum for GTFIS emerge as effective tools for flow pattern classification.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"192 ","pages":"Article 105378"},"PeriodicalIF":3.6,"publicationDate":"2025-07-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144711269","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}

{"title":"Effects of inflow conditions on plunging jet dynamics","authors":"Alexis Jamois ,&nbsp;Christian Okoye ,&nbsp;Ali Tehfe ,&nbsp;Gregory Guyot ,&nbsp;Martín Obligado","doi":"10.1016/j.ijmultiphaseflow.2025.105364","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105364","url":null,"abstract":"&lt;div&gt;&lt;div&gt;We present an experimental study on the influence of inflow characteristics on the dynamics of plunging jets. Several nozzle configurations were tested to establish a link between upstream conditions, the development of a water jet in air, and the subsequent bubble cloud generated upon impact with the water pool. Our study concerns jets with a nozzle diameter of &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mn&gt;7&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;6&lt;/mn&gt;&lt;mspace&gt;&lt;/mspace&gt;&lt;mi&gt;mm&lt;/mi&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; and fall heights up to 1.6 m. Both the impact of the nozzle geometry and the upstream pipe length were evaluated, covering inflow velocities within the range &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mrow&gt;&lt;mo&gt;(&lt;/mo&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;mo&gt;,&lt;/mo&gt;&lt;mn&gt;10&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;4&lt;/mn&gt;&lt;mo&gt;)&lt;/mo&gt;&lt;/mrow&gt;&lt;mspace&gt;&lt;/mspace&gt;&lt;mi&gt;m/s&lt;/mi&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;, Reynolds numbers in the range &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mo&gt;(&lt;/mo&gt;&lt;mn&gt;24&lt;/mn&gt;&lt;mspace&gt;&lt;/mspace&gt;&lt;mo&gt;×&lt;/mo&gt;&lt;mspace&gt;&lt;/mspace&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;msup&gt;&lt;mrow&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;3&lt;/mn&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;mo&gt;,&lt;/mo&gt;&lt;mn&gt;79&lt;/mn&gt;&lt;mspace&gt;&lt;/mspace&gt;&lt;mo&gt;×&lt;/mo&gt;&lt;mspace&gt;&lt;/mspace&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;msup&gt;&lt;mrow&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;3&lt;/mn&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;mo&gt;)&lt;/mo&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; and Weber numbers in the range &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mo&gt;(&lt;/mo&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;mo&gt;,&lt;/mo&gt;&lt;mn&gt;11&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;mo&gt;)&lt;/mo&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;. Complementary experimental techniques were applied to investigate several properties of the jet before and after the impact, that include optical probes, high-speed imaging and pressure sensors.&lt;/div&gt;&lt;div&gt;Differences between jets from a conical nozzle and a cylindrical nozzle with a sharp section change were examined. Our results show that the length of the pipe connected to the nozzle, that covers from 27 to 131 nozzle diameters, influences the jet’s breakup length, a phenomenon that increases with the pipe’s length. Moreover, this effect presents differences in terms of the nozzle properties, being stronger for the conical configuration. Furthermore, the breakup length is greater for the conical nozzle, whereas the cylindrical nozzle exhibits higher variability and more disturbances, leading to more extreme events. High-speed camera footage confirms that the jet from the cylindrical nozzle is rougher than that from the conical nozzle. Nevertheless, axial turbulence measurements do not differentiate between the two configurations, as all cases present small and similar values of turbulence intensity. Finally, the jet’s entrained airflow was analyzed in terms of penetration depth, bubble size, and mean velocity. This was achieved by means of an optical probe that can quantify the local void fraction and also the velocity of the air/water interface. We find that the conical nozzle produces a jet plume with a larger penetration depth, containing bubbles with smaller chords and velocity.&lt;/div&gt;&lt;div&gt;Globally, our study shows that the upstream conditions of a plunging jet are relevant for all studied quantities. Even a fully developed pipe inflow will be strongl","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"192 ","pages":"Article 105364"},"PeriodicalIF":3.6,"publicationDate":"2025-07-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144703138","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}

{"title":"Influence of in-cylinder airflow on fuel vaporization and mixture uniformity in compression ignition engines","authors":"Mohammad Nazemi Babadi ,&nbsp;Dong Kim ,&nbsp;Eunseop Yeom","doi":"10.1016/j.ijmultiphaseflow.2025.105373","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105373","url":null,"abstract":"<div><div>This study investigates the influence of in-cylinder airflow patterns and fuel-injection conditions on the performance of compression ignition engines through a cold simulation of diesel injection. A coupled simulation of the fuel system flow and spray formation was employed to analyze spray characteristics under various conditions. Initially, a zero-dimensional model was used to simulate the fuel system, followed by a three-dimensional analysis of fuel injection into the cylinder under different injection pressures and airflow patterns. Three types of in-cylinder airflows—swirl, tumble, and nonrotational— were considered to assess fuel distribution within the cylinder chamber. In addition, the effects of injection pressure on cylinder conditions and fuel vapor penetration were evaluated. The results indicate that increasing the injection pressure from 400 to 1600 bar enhances fuel vaporization, improving the vapor phase by approximately 0.4 g at the cycle end, indicating a more efficient mixing process. Furthermore, swirl flow promotes better air-fuel mixture uniformity compared to tumble and nonrotational flows, providing a higher volume fraction of fuel throughout the cylinder. Therefore, controlled increases in the injection pressure and the use of swirl flow improve engine efficiency.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"192 ","pages":"Article 105373"},"PeriodicalIF":3.6,"publicationDate":"2025-07-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144703139","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}

{"title":"Jet breakup dynamics of viscoelastic carboxymethyl cellulose solutions","authors":"Ketan Vinayak Warghat ,&nbsp;Yogesh Biswal ,&nbsp;Sukesh Sharma ,&nbsp;Pankaj Sharadchandra Kolhe ,&nbsp;Lakshmana Dora Chandrala ,&nbsp;Kirti Chandra Sahu","doi":"10.1016/j.ijmultiphaseflow.2025.105349","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105349","url":null,"abstract":"<div><div>We experimentally investigate the breakup dynamics of viscoelastic jets composed of carboxymethyl cellulose (CMC) solutions, focusing on the dripping and Rayleigh regimes at low flow rates. By varying the CMC concentration, needle diameter (<span><math><msub><mrow><mi>D</mi></mrow><mrow><mi>n</mi></mrow></msub></math></span>), and flow rate (<span><math><mi>Q</mi></math></span>), we analyze the effects of elasticity, viscosity, and flow conditions on jet stability and droplet formation. Our results show that increasing CMC concentration enhances viscoelastic effects, leading to prolonged jet lifetimes, extended liquid threads, and modified pinch-off behavior. At higher concentrations, elasticity suppresses capillary-driven instabilities, slowing thinning and facilitating the formation of beaded structures. We observe that the interplay between inertial, capillary, and elastic forces, influenced by CMC concentration, governs the jet length, droplet volume, and breakup time, with needle diameter and flow rate playing a crucial role in jet breakup phenomenon.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"192 ","pages":"Article 105349"},"PeriodicalIF":3.6,"publicationDate":"2025-07-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144679514","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}

{"title":"Modeling droplet size distributions in flashing sprays with 3D LES using an enhanced ELSA approach","authors":"Jan Wilhelm Gärtner,&nbsp;Andreas Kronenburg","doi":"10.1016/j.ijmultiphaseflow.2025.105356","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105356","url":null,"abstract":"<div><div>Flashing sprays play a critical role in high-altitude propulsion systems, where rapid phase transitions and complex transonic effects govern spray breakup and droplet formation. This study applies a novel Flashing Liquid Atomization Model (FLAM), within a hybrid Eulerian–Lagrangian framework to predict droplet size distributions at spray breakup. The governing equations of a one-fluid formulation for two-phase flows are solved on the Eulerian grid, while post-breakup droplets are tracked as Lagrangian particles. By incorporating surface density transport, the FLAM model eliminates the need to predefine droplet properties, instead providing locally determined droplet diameters. The droplet evaporation process is modeled as a combination of flash evaporation and diffusion, accounting for injection into conditions below the triple point. The approach is validated against experimental data from liquid nitrogen injection in near-vacuum conditions. Results reveal circumferential inhomogeneities in droplet size distributions, challenging the assumption of uniform atomization in flashing sprays. The three-dimensional Large Eddy Simulations (LES) capture turbulence-driven droplet collisions and shock-induced surface density destruction, leading to a more uniform droplet distribution while preserving the qualitative trends observed in previous two-dimensional Reynolds-Averaged Navier–Stokes (RANS) investigations. This study highlights the importance of capturing localized breakup physics for accurately modeling flashing sprays. The findings provide new insights into the interplay of phase change, turbulence, and transonic effects in cryogenic jet injection, contributing to the advancement of hybrid Eulerian–Lagrangian spray modeling for high-altitude propulsion systems.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"192 ","pages":"Article 105356"},"PeriodicalIF":3.6,"publicationDate":"2025-07-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144703279","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}

{"title":"Effects of wettability on bubble characteristics in air-water and molten-metal bubble columns using level-set volume-of-fluid computational fluid dynamics","authors":"Son Ich Ngo ,&nbsp;Young-Il Lim ,&nbsp;Uen-Do Lee ,&nbsp;Youngjae Lee ,&nbsp;Sung Won Kim","doi":"10.1016/j.ijmultiphaseflow.2025.105369","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105369","url":null,"abstract":"<div><div>This study compares bubble characteristics in wetting air-water bubble columns (AWBCs) and non-wetting N₂-Sn molten metal bubble columns (MMBCs) across bubbling and transient flow regimes using two gas injector types, aiming to guide mmBC reactor design where experimental data are limited. A level-set volume-of-fluid (LS-VOF) computational fluid dynamics (CFD) model was used to sharply track the interface between the gas and liquid phases. A mesh independence test was performed to identify a reasonable mesh density. The LS-VOF model was then validated against experimental bubble size data for the air-water and Ar-Fe systems. The gas holdup (<span><math><msub><mi>α</mi><mi>G</mi></msub></math></span>), Sauter mean bubble diameter (<span><math><msub><mi>d</mi><mn>32</mn></msub></math></span>), and specific interfacial area (<span><math><msub><mi>a</mi><mi>s</mi></msub></math></span>) were compared in AWBCs andMMBCs, which were equipped with either a single-hole nozzle or plate, at superficial gas velocities (<em>u_G</em>) of 3.4 (bubbling regime) and 57.8 mm/s (transient regime). At <em>u_G</em> = 3.4 mm/s, unimodal bubble size distributions (BSDs) were observed for the AWBCs andMMBCs. Under the transient flow regime, the AWBCs andMMBCs exhibited bimodal BSDs with almost identical hydrodynamic parameters (<span><math><msub><mi>α</mi><mi>G</mi></msub></math></span>, d₃₂, and <em>a_s</em>), which was attributed to the similar ratio of liquid density (<em>ρ_L</em>) to surface tension (<em>σ</em>) in the systems. In the bubble-shape diagram plotted on the plane of the Eötvös and Reynolds numbers, the AWBCs andMMBCs exhibited ellipsoidal wobbling bubbles, with distinctions identified based on the Morton number. This study offers valuable insights into the similarities and differences between AWBCs andMMBCs under the bubbling and transient flow regimes.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"192 ","pages":"Article 105369"},"PeriodicalIF":3.6,"publicationDate":"2025-07-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144685618","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}

{"title":"Displacement flow inside a capillary tube — the impact of boundary conditions on the dynamic contact angle","authors":"A. Koźluk ,&nbsp;M. Klamka ,&nbsp;M. Remer ,&nbsp;M. Rutkowski ,&nbsp;T. Bobinski","doi":"10.1016/j.ijmultiphaseflow.2025.105338","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105338","url":null,"abstract":"<div><div>Accurately modelling multiphase flows requires a thorough understanding of advancing contact line behaviour, which is crucial for predicting interface dynamics in applications like microfluidics and coating processes. This research investigates how the contact angle boundary condition and slip length influence the dynamic contact angle and interface shape within a horizontal cylindrical capillary tube at low velocities. We conduct numerical simulations of Newtonian fluid flow using the volume of fluid (VOF) method to analyse the impact of these factors across different length scales. We explore three approaches for specifying the contact angle at the triple line, comparing velocity-dependent and velocity-independent models. Our results indicate that employing a velocity-dependent relation reduces the critical capillary number for air entrainment and overestimates the apparent contact angle compared to Hoffman’s experimental findings. Imposing a contact angle based on Kistler’s relation enlarges the viscous bending zone compared to the constant contact angle model. Additionally, increasing slip length influences the apparent contact angle differently depending on the contact angle model used. The best agreement with experimental data is achieved using a constant quasi-static advancing contact angle in the low to intermediate capillary number range. A detailed analysis of the interface shape highlights the role of slip length in regulating viscous bending extent. These findings offer valuable insights for enhancing the accuracy of numerical simulations of multiphase flows involving contact lines, with significant implications for practical applications.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"192 ","pages":"Article 105338"},"PeriodicalIF":3.6,"publicationDate":"2025-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144679513","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}

{"title":"Entrainment characteristics of a swirling liquid jet plunging in a quiescent pool of liquid","authors":"Toshan lal Sahu ,&nbsp;Ujjwal Chetan ,&nbsp;Saurabh Dhopeshwar ,&nbsp;Prabir Kumar Kar ,&nbsp;P. Das ,&nbsp;Rajaram Lakkaraju","doi":"10.1016/j.ijmultiphaseflow.2025.105353","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105353","url":null,"abstract":"<div><div>We have explored the entrainment characteristics of a swirling liquid jet plunging into a quiescent liquid pool. We carried out three-dimensional simulations for a range of swirl parameters <span><math><mrow><mn>0</mn><mo>.</mo><mn>5</mn><mo>≤</mo><mi>S</mi><mo>≤</mo><mn>1</mn><mo>.</mo><mn>6</mn></mrow></math></span> and axial Reynolds number of <span><math><mrow><mn>4000</mn><mo>≤</mo><mi>R</mi><mi>e</mi><mo>≤</mo><mn>12000</mn></mrow></math></span>. The main objective of the current investigation is to explore the impact of the swirl parameter on the entrainment characteristics of a swirling plunging jet. The results indicate that the air volume consistently increases up to a swirl parameter of <span><math><mrow><mi>S</mi><mo>=</mo><mn>1</mn><mo>.</mo><mn>2</mn></mrow></math></span>, beyond which it decreases for a fixed Reynolds number. The amount of air being entrained depends upon the trade-off between the axial inertia in competition with radial inertia and buoyancy. We have delineated the mechanism of transition through turbulent kinetic energy possessed by the swirling liquid jet for the range of swirl parameters considered. Further, the bubble penetration depth decreases with increasing swirl parameters. We also identified the breakup morphology of the initial air-cavity pinching-off into smaller air bubbles for the case of swirling plunging jets and compared it with their non-rotating counterpart.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"192 ","pages":"Article 105353"},"PeriodicalIF":3.6,"publicationDate":"2025-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144656720","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}

{"title":"Numerical analysis of binary molten glass microspheres droplets co-directional collision behavior","authors":"Xiaolei Hu,&nbsp;Liangyu Tao,&nbsp;Wei Li,&nbsp;Jiayi Guo,&nbsp;Zhenzhen Liu,&nbsp;Nenggang Xie,&nbsp;Baohong Tong","doi":"10.1016/j.ijmultiphaseflow.2025.105366","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105366","url":null,"abstract":"<div><div>The co-directional collision behavior of molten glass microspheres plays a crucial role in determining their sphericity and physical properties. Previous studies have predominantly examined head-on collisions of counter-moving droplets. However, the mechanisms governing co-directional collisions remain inadequately understood. To bridge this gap, a three-dimensional numerical model was developed using the open-source solver <em>Basilisk</em>, which incorporates the volume-of-fluid (VOF) method with adaptive mesh refinement (AMR), to simulate molten glass microsphere collisions. In comparison with experimental observations, the effects of velocity ratio and radius ratio on co-directional collision dynamics were systematically investigated through detailed analyses of droplet morphology evolution, velocity fields, and pressure distributions. Five distinct collision regimes are identified: (Ⅰ) bouncing, (Ⅱ) coalescence, (Ⅲ) reflexive separation without satellite droplets, (Ⅳ) reflexive separation with a single satellite droplet, and (Ⅴ) reflexive separation with an ejected satellite droplet. The results demonstrated that increasing the velocity ratio shifts collision outcomes from bouncing or coalescence to reflexive separation. Satellite droplet formation was observed only at high velocity ratios when the radius ratio approaches unity, whereas a significant droplet size disparity promoted coalescence. Additionally, the transformation between kinetic energy (<em>KE</em>) and surface energy (<em>SE</em>) before and after collision was analyzed. The findings revealed that <em>KE</em> was initially converted into <em>SE</em> upon impact and subsequently partially transformed back into <em>KE</em> during axial stretching. A regime map was constructed to classify collision outcomes, highlighting the pivotal role of velocity and radius ratios in regime transitions. This study provides theoretical insights to support the optimization of molten glass microsphere production processes.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"192 ","pages":"Article 105366"},"PeriodicalIF":3.6,"publicationDate":"2025-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144631778","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}