International Journal of Multiphase Flow最新文献

{"title":"Dynamics of electrocoalescence-induced microfluidic droplet merging: Influence of the applied electric field","authors":"Aliasghar Mohammadi,&nbsp;Mehdi Moradi,&nbsp;Farshad Raji","doi":"10.1016/j.ijmultiphaseflow.2025.105135","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105135","url":null,"abstract":"<div><div>Merging droplets in microchannels is an essential task in a variety of microfluidic systems. In this study, the electrocoalescence of droplets dispersed in an otherwise immiscible fluid within a microfluidic device was investigated numerically. The microfluidic device, comprising a flow-focusing junction, was employed to generate droplets in an otherwise immiscible fluid. Subsequently, the generated droplets were directed over a series of microelectrodes. The continuous and dispersed phases were modeled as incompressible Newtonian fluids. The interface between the phases was tracked using a phase-field model. For a constant electric field, three distinct threshold voltages were identified. No droplet merging was observed at voltages less than the first threshold-voltage. The regular merging of three droplets was noted at voltages beyond the second threshold-voltage and less than the third threshold-voltage. The irregular merging of droplets occurs at voltages beyond the third threshold-voltage. The influence of the interfacial tension on the first threshold-voltage was examined for the constant electric field. The interfacial tension considerably modulates the first threshold-voltage. Investigations were also conducted on the mechanism of droplet coalescence under alternating and pulsed direct-current electric fields, along with the effect of frequency on the first threshold-voltage. The first threshold-voltage increases with increasing frequency in both electric fields. Generally, the effects of frequency are small compared with, for example, the influences of interfacial tension on the first threshold-voltage.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"185 ","pages":"Article 105135"},"PeriodicalIF":3.6,"publicationDate":"2025-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143143850","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":"Bubbles climbing on two vertical superhydrophobic sticks","authors":"Pengfei Du ,&nbsp;Chengxu Tu ,&nbsp;Yukun Wang ,&nbsp;Yalei Zhao ,&nbsp;Ji Chen ,&nbsp;Jianzhong Lin ,&nbsp;Fubing Bao","doi":"10.1016/j.ijmultiphaseflow.2025.105133","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105133","url":null,"abstract":"<div><div>Bubble manipulation using superhydrophobic surfaces (SBS) is currently a subject of extensive research. Although flat surfaces have been the primary focus of investigation, with dimensions significantly larger than those of the bubbles, there has been limited attention given to the study of long slender SBSs, such as filaments and thin rods, which closely approximate the size of the bubbles. However, these elongated SBSs hold promise for enabling a wider range of bubble motion modes and an increased surface area for the bubbles. This study introduces the concept of double superhydrophobic sticks (DSBS) as a novel method to enhance the rising velocity (<em>U</em>) of buoyancy-driven bubbles. The examination identifies three distinct bubble configurations on the DSBS: nut-shaped, bell-shaped, and apple-shaped. Remarkably, the DSBS exhibits exceptional superaerophilicity, achieving a threefold increase in <em>U</em> for larger bubbles (with a diameter of approximately 4 mm). Prior research has already established the substantial impact of the length of the moving three-phase contact line (MCL) on the migration velocity of bubbles sliding on diverse planar SBSs. In contrast, our findings indicate that even the MCL length remains constant, the rising velocity of bubbles on DSBSs can be modulated by varying both the bubble size, the spacing between double sticks (<em>S</em>), and the diameter of the stick (<em>D</em>_s). Specifically, <em>U</em> is dependent on a revised Ohnesorge number (<span><math><mrow><mi>O</mi><msup><mrow><mi>h</mi></mrow><mo>*</mo></msup><mo>=</mo><msup><mrow><mi>L</mi></mrow><mo>*</mo></msup><mfrac><mi>μ</mi><msqrt><mrow><mi>ρ</mi><mi>σ</mi><mi>S</mi></mrow></msqrt></mfrac></mrow></math></span>), following a log-linear-scaling relationship with <em>U</em>. Considering the altered impact of the <em>S</em> on the bubble shape, we propose the <em>S</em> as the characteristic length and the shape correction factor <em>L</em>* (<span><math><mrow><msup><mrow><mi>L</mi></mrow><mo>*</mo></msup><mo>=</mo><mrow><mn>1</mn><mo>/</mo><msup><mrow><mrow><mi>ε</mi></mrow></mrow><mo>*</mo></msup></mrow><mo>=</mo><mrow><msub><mi>d</mi><mtext>eq</mtext></msub><mo>/</mo><mi>S</mi></mrow></mrow></math></span>) for the revised Ohnesorge number. Here, <em>d</em>_eq is the equivalent diameter of the bubble, <em>ε</em>* is the normalized stick gap ratio. The scaling law identified in this investigation effectively enables the simultaneous prediction of both the morphology and rising velocity of bubbles on the double sticks. Hence, our bubble manipulation method and its associated predictive model exhibits promising prospects for implementation across a range of gas-liquid systems, encompassing improved electrolytic hydrogen production, gas-liquid separation, adjustable flotation, and advanced surface chemistry.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"185 ","pages":"Article 105133"},"PeriodicalIF":3.6,"publicationDate":"2025-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143143844","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":"Enhanced Level-Set Method for free surface flow applications","authors":"Paulin Ferro,&nbsp;Paul Landel,&nbsp;Carla Landrodie,&nbsp;Simon Guillot,&nbsp;Marc Pescheux","doi":"10.1016/j.ijmultiphaseflow.2025.105126","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105126","url":null,"abstract":"<div><div>This publication presents a solver using the Level-Set method (Sussman et al., 1994) for incompressible two phase flows with surface tension. A one fluid approach is adopted where both phases share the same velocity and pressure field. The Ghost Fluid Method (Fedkiw et al., 1999) is also used. An efficient and pragmatic solution is proposed to avoid interface displacement during the reinitialization of the Level-Set field. A solver called <em>LSFoam</em> is created in the OpenFOAM (Weller et al., 1998) framework with a consistent Rhie &amp; Chow interpolation (Cubero and Fueyo, 2007). This solver is tested on several test cases, covering different scales and flow configurations: rising bubble test case, Hysing et al. (2007), Rayleigh–Taylor instability simulations (Puckett et al., 1997), Ogee spillway flow (Erpicum et al., 2018), 3D dambreak simulation with a square cylinder obstacle (Gomez-Gesteira, 2013) and KVLCC2 steady resistance calculations (Larsson et al., 2014). Overall results are in excellent agreement with reference data and the present approach is very promising for moderate free surface deformations.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"185 ","pages":"Article 105126"},"PeriodicalIF":3.6,"publicationDate":"2025-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143143847","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":"Investigation of single saltwater droplet impact solidification and prediction method for macroscopic ice accretion on a flat surface","authors":"Xiaogang Liu ,&nbsp;Yangbo Li ,&nbsp;Yanhua Wang ,&nbsp;Zhongyi Wang ,&nbsp;Khoo Boo Cheong","doi":"10.1016/j.ijmultiphaseflow.2025.105128","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105128","url":null,"abstract":"<div><div>Seawater droplet freezing threatens offshore structures, vessels and marine engine air intake systems. Yet, single droplet freezing and its link to macroscopic ice accretion are poorly understood. The paper investigates the impact of single supercooled saltwater droplets on a flat surface as its starting point. It employs the Coupled Level-Set and Volume-of-Fluid (CLSVOF) and Enthalpy-Porosity (EP) method to establish a numerical model for droplet impact freezing. The study analyzes various factors affecting single droplet spreading flow characteristics, transient heat transfer properties, and impact freezing dynamics. A mechanism equating the dimensionless impact time of a single droplet to the dimensionless impact time interval between multiple droplets is established. Moreover, a mathematical model predicting ice thickness on flat surfaces is proposed based on the freezing fraction corresponding to the Liquid Water Content (LWC) of single droplet. Finally, experimental results of ice accretion thickness on flat panel (ice blade) were obtained under different parametric conditions in an ice tunnel. Through comparative analysis, the validity of the proposed method for predicting ice accretion thickness on flat surfaces was confirmed. This predictive method effectively considers various factors such as salinity, velocity, temperature, and diameter, providing valuable insights for studying ice accretion on flat panels or the surfaces of complex structures.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"185 ","pages":"Article 105128"},"PeriodicalIF":3.6,"publicationDate":"2025-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143143892","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":"A physics-inspired neural network to model higher order hydrodynamic interactions in heterogeneous suspensions","authors":"Layal Jbara ,&nbsp;Zihao Cheng ,&nbsp;Anthony Wachs","doi":"10.1016/j.ijmultiphaseflow.2025.105131","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105131","url":null,"abstract":"&lt;div&gt;&lt;div&gt;We propose a novel physics-inspired, data-driven framework for modeling particle-laden flows that conceptually overcomes the limitations of conventional methods. By building on the hierarchical model of Siddani and Balachandar (Siddani and Balachandar, 2023), our framework incorporates global and local heterogeneities and integrates higher-order interactions. We leverage machine learning, to first sequentially train neural networks to predict isolated &lt;span&gt;&lt;math&gt;&lt;mi&gt;n&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt;-order interactions for &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mo&gt;(&lt;/mo&gt;&lt;mi&gt;N&lt;/mi&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mi&gt;n&lt;/mi&gt;&lt;mo&gt;)&lt;/mo&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;-body systems. We then feed the information obtained from binary &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;n&lt;/mi&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;, ternary &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;n&lt;/mi&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mn&gt;3&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; and quaternary &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;n&lt;/mi&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mn&gt;4&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; interactions to a suspension neural network, with an architecture featuring distinct, shared blocks for each &lt;span&gt;&lt;math&gt;&lt;mi&gt;n&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt; interaction order and linear activation to integrate interactions of varying orders. Our findings demonstrate significant promise in capturing the hydrodynamic disturbances within suspensions of homogeneous and stepwise heterogeneous test cases. Specifically, our study indicates that the reformulated Quaternary Hierarchical Model (QHM), which incorporates four hierarchical structures (based on unary, binary, ternary, and quaternary interactions), provides promising results in predicting the forces and torques experienced by a reference particle. By varying the number of neighboring particles and interaction orders, the QHM consistently outperforms the Binary and Ternary Hierarchical Models, achieving testing &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mo&gt;〈&lt;/mo&gt;&lt;msup&gt;&lt;mrow&gt;&lt;mi&gt;R&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;mo&gt;〉&lt;/mo&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; values of 0.738, 0.752, and 0.829 for streamwise drag force &lt;span&gt;&lt;math&gt;&lt;msubsup&gt;&lt;mrow&gt;&lt;mi&gt;F&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;x&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;i&lt;/mi&gt;&lt;/mrow&gt;&lt;/msubsup&gt;&lt;/math&gt;&lt;/span&gt;, transverse lift force &lt;span&gt;&lt;math&gt;&lt;msubsup&gt;&lt;mrow&gt;&lt;mi&gt;F&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;y&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;i&lt;/mi&gt;&lt;/mrow&gt;&lt;/msubsup&gt;&lt;/math&gt;&lt;/span&gt; and transverse torque &lt;span&gt;&lt;math&gt;&lt;msubsup&gt;&lt;mrow&gt;&lt;mi&gt;T&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;⊥&lt;/mo&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;i&lt;/mi&gt;&lt;/mrow&gt;&lt;/msubsup&gt;&lt;/math&gt;&lt;/span&gt;, respectively. Optimizing both the number of neighbors and interaction order is crucial for maximizing the model performance, especially for predicting &lt;span&gt;&lt;math&gt;&lt;msubsup&gt;&lt;mrow&gt;&lt;mi&gt;F&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;x&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;i&lt;/mi&gt;&lt;/mrow&gt;&lt;/msubsup&gt;&lt;/math&gt;&lt;/span&gt;. To predict &lt;span&gt;&lt;math&gt;&lt;msubsup&gt;&lt;mrow&gt;&lt;mi&gt;F&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;y&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;i&lt;/mi&gt;&lt;/mrow&gt;&lt;/msubsup&gt;&lt;/math&gt;&lt;/span&gt; and &lt;span&gt;&lt;math&gt;&lt;msubsup&gt;&lt;mrow&gt;&lt;mi&gt;T&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;⊥&lt;/mo&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;i&lt;/mi&gt;&lt;/mrow&gt;&lt;/msubsup&gt;&lt;/math&gt;&lt;/span&gt;, the interaction order with neighboring particles significantly affects performance, with higher-order interactions proving more critical th","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"185 ","pages":"Article 105131"},"PeriodicalIF":3.6,"publicationDate":"2025-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143143843","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":"Conditions and characteristics of the coal-water fuel droplets fragmentation in high-speed airflow","authors":"G.V. Kuznetsov,&nbsp;S.V. Syrodoy,&nbsp;Zh.A. Kostoreva,&nbsp;R.R. Zamaltdinov,&nbsp;K.A. Voytkova","doi":"10.1016/j.ijmultiphaseflow.2025.105125","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105125","url":null,"abstract":"<div><div>The article presents the results of experimental studies of the processes of crushing typical droplets of coal-water fuel in an air flow. Fragmentation modes have been established depending on the concentration (φ) of the solid combustible component in the fuel composition. It has been established that the critical Weber number (We) significantly depends on the concentration of coal in the suspension. In this case, the We(φ) dependence has a significantly nonlinear “hockey stick” type with a threshold value of φ≥50 %. When the concentration of coal in suspension is up to 50 % (by weight), the characteristics and fragmentation conditions (floating speed) of the drops are practically no different from the similar characteristics of the process of fragmentation water drops. At φ≥50 %, the values of critical Weber numbers for CWF droplets increase significantly. The influence of the type of coal on the characteristics and conditions of fragmentation droplets of coal-water fuel was also analyzed. It has been established that an increase in the degree of coal metamorphism leads to an improvement in the process of fragmentation a drop of coal-water fuel.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"185 ","pages":"Article 105125"},"PeriodicalIF":3.6,"publicationDate":"2025-01-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143143842","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 validation of a numerical model for the analysis of erosion depth in coarse sand induced by a dam break of water","authors":"Benjamín Fuentes,&nbsp;Marcela Cruchaga,&nbsp;Jonathan Núñez","doi":"10.1016/j.ijmultiphaseflow.2024.105118","DOIUrl":"10.1016/j.ijmultiphaseflow.2024.105118","url":null,"abstract":"<div><div>A computational model for studying the scour depth of coarse sand generated by a dam break is presented and validated using data obtained from an original experiment also reported in this work. The experimental study includes sand characterization. Different aspect ratios for the fluid column heights of the dam break are considered to provide data for evaluating how operating parameters affect the evolution of the free surface (water–air interface) and sand erosion (sand interface). The experiments are video recorded, and the opening speeds of the gate, free surface, and scour depths are measured using image processing techniques from the videos registered. The simulations are performed in the framework of an open-source software with the Smoothed Particle Hydrodynamics method (SPH). The coarse sand is described as a non-Newtonian fluid. A unique set of numerical parameters used in modelling is determined to adequately describe the whole set of cases. The experiments demonstrate that the scour of the sand is affected by the aspect ratio of the dam break. Despite the opening speed of the gate experimentally presenting fluctuations, this aspect does not affect the scour of sand in the speed range analysed. The results show that the scour depths of the studied sand increase as the aspect ratio increases. These experimental facts are also observed from the numerical analysis. Moreover, a good statistical agreement is obtained between experimental data and the numerical predictions for the free surface and the scour depth evolutions. These allow us to validate the proposed three-dimensional numerical model.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"185 ","pages":"Article 105118"},"PeriodicalIF":3.6,"publicationDate":"2025-01-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143144262","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 study of air–water flow properties in the breaking roller of dam-break waves","authors":"D. Regout,&nbsp;S.N. Jonkman,&nbsp;D. Wüthrich","doi":"10.1016/j.ijmultiphaseflow.2024.105119","DOIUrl":"10.1016/j.ijmultiphaseflow.2024.105119","url":null,"abstract":"<div><div>Dam-break waves are highly unsteady long-wave phenomena, characterized by a breaking front with a strong recirculating air–water mixture. While the air–water flow properties of steady flows have often been investigated, the understanding of dynamic processes in unsteady multiphase flows remains limited. In this experimental study, a new approach was implemented to analyze the air–water flow properties of highly unsteady flows in the form of dam-break waves using ensemble-averaging techniques to account for short-duration measurements. The new dataset includes four different flow conditions, providing novel insights into the relation between various hydrodynamic characteristics and key air–water flow properties, including bubble characteristics and void fraction. The void fraction profiles indicated the presence of a turbulent shear layer along with a recirculation zone close to the free surface, showing analogies with similar steady and unsteady flow phenomena. Variations in the Froude number were shown to strongly affect the number and size of air bubbles, particularly in the shear layer. Higher depth-averaged air concentrations were found with increasing Froude numbers, reaching up to 40% for Fr = 5.14. Overall, the results confirm the importance of considering the presence of air in dam-break waves and demonstrate the suitability of this new methodology for investigating air–water flow properties in highly turbulent flows. They offer a deeper understanding of the multiphase nature of dam-break waves, which is relevant for a wide range of processes in coastal and hydraulic engineering.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"185 ","pages":"Article 105119"},"PeriodicalIF":3.6,"publicationDate":"2025-01-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143144875","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Coalescence dynamics of a nanoparticle-laden droplet at oil-water interface under electric field: A molecular dynamics simulation","authors":"Bin Li ,&nbsp;Yan Wu ,&nbsp;Xiaohui Dou ,&nbsp;Wei Xiang ,&nbsp;Hai Wang ,&nbsp;Zhiqian Sun ,&nbsp;Zhentao Wang ,&nbsp;Junfeng Wang","doi":"10.1016/j.ijmultiphaseflow.2025.105129","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105129","url":null,"abstract":"<div><div>Droplet deformation, coalescence, sedimentation and droplet-interface coalescence are common phenomena during crude oil electrodehydration. This paper investigates the coalescence dynamics of a nanoparticle-laden (<em>NP</em>-laden) water droplet at the oil-water interface under direct current (<em>DC</em>), alternating current (<em>AC</em>), and pulsed (<em>PE</em>) electric fields, using molecular dynamics (<em>MD</em>) method. Validation studies demonstrate strong quantitative and qualitative agreement between the experimental and numerical results. The results show that complete droplet-interface coalescence (<em>CC</em>), encompassing both typical and upheaval modes, as well as partial coalescence (<em>PC</em>), occurs under <em>DC</em> fields and is influenced by ion migration mechanisms. The critical cone angle transitioning from <em>CC</em> mode to <em>PC</em> mode is 47.03°, and the critical electric capillary number (<em>Ca_E</em>) decreases with increasing droplet-interface distance. Moreover, a robust quartic polynomial function relationship between dimensionless liquid bridge width <em>W*</em> and dimensionless time <em>t*</em> is established to describe liquid bridge evolution. The occurrence of <em>CC</em> mode is significantly more pronounced under <em>AC</em> and pulsed fields compared to <em>DC</em> fields. The optimal dimensionless frequencies are identified as <em>f*</em>=16 for <em>AC</em> fields and <em>f*</em>=25 for pulsed fields. Total interactions (<em>TI</em>) analysis shows that the coalescence efficiencies rank as follows: <em>PE</em> &gt; <em>DC</em> &gt; <em>AC</em>. The findings of this study offer significant potential for optimizing high-efficiency and compact electrostatic coalescence equipment.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"184 ","pages":"Article 105129"},"PeriodicalIF":3.6,"publicationDate":"2025-01-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143137941","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 orifice height and gas flow rate on underwater bubbles dynamics in crossflow","authors":"Han-bin Wang ,&nbsp;Yang Xu ,&nbsp;Si-ying Li","doi":"10.1016/j.ijmultiphaseflow.2025.105127","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105127","url":null,"abstract":"<div><div>This study employs high-speed photography and image processing to investigate the effects of orifice heights (<span><math><mrow><msub><mi>H</mi><mi>n</mi></msub><mo>/</mo><mi>δ</mi></mrow></math></span> = 0, 0.5, and 2, where <span><math><mi>δ</mi></math></span> represents the boundary layer thickness) and gas flow rates (<em>Q_g</em> = 0.5, 2, and 10 L/min) on bubble dynamics in crossflow. Results indicate that higher gas flow rates extend bubble formation time, enlarge the bubble diameter, increase the terminal rising velocity, and reduce the trajectory inclination angle. Additionally, greater orifice height accelerates liquid flow at the orifice. This acceleration leads to earlier bubble detachment, which reduces the bubble diameter, increases the trajectory inclination angle, and lowers the terminal rising velocity. Furthermore, a mathematical model was developed to comprehensively describe the entire process of bubble formation and rising, accurately predicting kinematic parameters such as bubble velocities and the forces acting on the bubble. In the formation stage, the model agrees well with experimental data (error ∼ 10%), identifying buoyancy <span><math><msub><mi>F</mi><mi>B</mi></msub></math></span> and mass-related inertial force <span><math><msub><mi>F</mi><mrow><mi>I</mi><mi>m</mi><mi>x</mi></mrow></msub></math></span> as the dominant detachment force in rising and streamwise direction, respectively. In the rising stage, the model incorporates a terminal velocity correction to account for the impact of preceding bubbles, significantly enhancing accuracy (error &lt; 7%). It identifies <span><math><msub><mi>F</mi><mi>B</mi></msub></math></span>, suction from preceding bubbles <span><math><msub><mi>F</mi><mi>w</mi></msub></math></span>, and drag <span><math><msub><mi>F</mi><mrow><mi>D</mi><mi>y</mi></mrow></msub></math></span> as the key factors affecting the rising velocity. Meanwhile, forces in the streamwise direction are minimal as the terminal streamwise velocity approaches the incoming flow velocity. These findings significantly enhance our understanding of bubble dynamics under crossflow, providing valuable insights for optimizing industrial processes involving gas-liquid interactions.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"184 ","pages":"Article 105127"},"PeriodicalIF":3.6,"publicationDate":"2025-01-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143137939","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}