International Journal of Multiphase Flow最新文献

{"title":"Direct Numerical Simulation of collision events in flotation under the influence of gravity","authors":"Benedikt Tiedemann ,&nbsp;Jochen Fröhlich","doi":"10.1016/j.ijmultiphaseflow.2025.105204","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105204","url":null,"abstract":"<div><div>Collisions between particles and bubbles are decisive for the performance of flotation processes. In this work Direct Numerical Simulations of a prototypical gravitation-driven flotation process are presented with bubbles fully resolved and modelled as rigid spheres while the solid-phase is represented as point-particles. Key bubble and particle parameters correspond to realistic setups and are varied to study their effect on the collision rate. The study addresses the main influencing parameters, such as bubble diameter, gas hold-up, particle diameter, and particle density. Locally around the bubble significant differences of the collision behaviour exist. Most collisions occur on the upper bubble half, but some also on the lower bubble half. This is caused by a high particle-bubble relative velocity towards the bubble from the upper bubble half and an accumulation of particles at these locations as they deviate around the bubble. The paper provides reference data for flotation modelling.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"188 ","pages":"Article 105204"},"PeriodicalIF":3.6,"publicationDate":"2025-03-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143681983","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":"Hollow droplet impact on a micro-trench hydrophilic surface","authors":"Lijuan Qian,&nbsp;Cheng Li,&nbsp;Chenlin Zhu","doi":"10.1016/j.ijmultiphaseflow.2025.105198","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105198","url":null,"abstract":"<div><div>Hollow droplet impact on a solid surface occurs in applications ranging from controllable bio-medicine, thermal spray coating and additive manufacturing. In this work, we experimentally study the impact dynamics of silicone oil hollow droplets on a hydrophilic solid substrate, including a smooth surface and a micro-trench surface. The size of the total droplet and the air bubble are kept constant and we investigate the influence of the location of the air bubble, impact velocity, and micro-trench structure on the hollow droplet shape evolution. The results show that a counter-jet formed after the hollow droplet impact on a solid surface and the height of the counter-jet and the spreading diameter of the lamella grow with impact velocity. Two cavity break mode, natural crashing and external crashing, are found in our experiment and the critical Weber number <span><math><mrow><mi>W</mi><mi>e</mi></mrow></math></span> is around 40. When <span><math><mrow><mi>W</mi><mi>e</mi></mrow></math></span> reaches 70, the counter-jet clamps off and detaches from the surface. For a given hollow droplet, the spreading characteristics do not vary significantly with different locations of the air bubble, while the height of the central counter-jet increased with the increasing eccentricity. The effects of gap width and height of the micro-trench are discussed. The structured surfaces reduce the maximum spreading diameter compared to smooth surfaces. A theoretical model considering energy conversation is established to predict the maximum spreading diameter. The deviation between the predicted value and the measured value is less than 10%, which shows excellent consistency. These findings offer critical insights into the behavior of hollow droplets and hold significant potential for applications requiring precise droplet manipulation.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"188 ","pages":"Article 105198"},"PeriodicalIF":3.6,"publicationDate":"2025-03-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143609659","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":"Twin experiments for data assimilation of cavitating flow around a hydrofoil","authors":"Shungo Okamura,&nbsp;Kie Okabayashi","doi":"10.1016/j.ijmultiphaseflow.2025.105201","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105201","url":null,"abstract":"<div><div>Twin experiments are conducted to clarify whether assimilation effects can be achieved by data assimilation (DA) with measurement data obtained by existing cavitation flow measurement techniques. The analysis object is the cavitation flow around a Clark-Y11.7% hydrofoil. The pseudo-measurement data are velocity fields from tomographic particle image velocimetry (TPIV) or two-dimensional PIV, both containing missing data in cavity, along with indirectly obtained cavity interface shapes. A large-eddy simulation is used for unsteady simulation of cavitating turbulent flow, and a local ensemble transform Kalman filter is used as the DA method. Visualized flow fields of the ensemble mean show that characteristic phenomena of the pseudo-measurement data are qualitatively reproduced. In addition, the time-series data at an observation point located at the position where the pseudo-measurement data exists converged following the pseudo-measurement data. The velocity inside the cavity, where no pseudo-measurement data exists, is also complemented by CFD that incorporates information from outside of the cavity. However, the complementation performance depends on the accuracy of the cavitation model. This DA program is applied to the real PIV data of single-phase flow and qualitatively reproduces the flow field. Furthermore, the observation noise is reduced and the data outside the measurement domain are complemented.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"188 ","pages":"Article 105201"},"PeriodicalIF":3.6,"publicationDate":"2025-03-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143620171","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":"Transient bubble rising in the presence of a surfactant at very low concentrations","authors":"D. Fernández-Martínez ,&nbsp;M.G. Cabezas ,&nbsp;J.M. López-Herrera ,&nbsp;M.A. Herrada ,&nbsp;J.M. Montanero","doi":"10.1016/j.ijmultiphaseflow.2025.105205","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105205","url":null,"abstract":"<div><div>We study the formation of the dynamic adsorption layer when a bubble is released in a tank containing water with a tiny amount of surfactant. The influence of the sorption kinetic constants is examined by comparing the experiments with Sodium Dodecyl Sulfate (SDS) and Triton X-100. The experiments allowed us to determine the parameter conditions that lead to a stable bubble rising and to validate the simulation. A simple scaling analysis and the simulation show that the formation of the dynamic adsorption layer can be split into three phases characterized by disparate time scales. The mechanisms controlling those phases are surfactant convection, adsorption–desorption, and diffusion. The amount of surfactant adsorbed onto the interface increases monotonously throughout the three phases. The experiments and the simulation show that the rising velocity reaches a maximum at times of the order of <span><math><msubsup><mrow><mi>k</mi></mrow><mrow><mi>d</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msubsup></math></span> (<span><math><msub><mrow><mi>k</mi></mrow><mrow><mi>d</mi></mrow></msub></math></span> is the desorption constant) when the dynamic adsorption layer is practically formed. This occurs even when only traces of surfactant are present in the liquid. The non-monotonous behavior of the maximum surfactant surface concentration is explained in terms of the reverse flow in the rear of the bubble right after the bubble release. This work contributes to the understanding of the complex interplay between hydrodynamics and surfactant transport and kinetics over bubble rising.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"188 ","pages":"Article 105205"},"PeriodicalIF":3.6,"publicationDate":"2025-03-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143620170","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":"Exploring the influence of surface microstructures on cloud cavitation control: A numerical investigation","authors":"Vahid Velayati ,&nbsp;Khodayar Javadi ,&nbsp;Bettar Ould-el-Moctar","doi":"10.1016/j.ijmultiphaseflow.2025.105206","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105206","url":null,"abstract":"<div><div>This study explores the influence of surface microstructures, on controlling cloud cavitation dynamics over a three-dimensional Clark Y hydrofoil. The investigation focuses on the effects of rows of semi-spherical microstructures, strategically placed at three different locations on the hydrofoil's suction side. The study utilizes the Large Eddy Simulation (LES) approach to investigate the influence of these configurations on the cloud cavitation lifecycle, focusing on aspects such as cloud shedding frequency, hydrofoil efficiency, cavitation volume, and overall unsteadiness. The Reynolds number is considered to be <span><math><mrow><mn>7</mn><mspace></mspace><mo>×</mo><mspace></mspace><msup><mrow><mn>10</mn></mrow><mn>5</mn></msup><mspace></mspace></mrow></math></span>and the angle of attack of the hydrofoil is fixed at 8 degrees. The results showed that placing the microstructures near the leading edge prolonged the sheet cavity and reduced the cloud cavitation shedding frequency by 5 %. However, this configuration also resulted in an 11.45 % decrease in the lift-to-drag ratio. Positioning semi-spherical microstructures along the mid-chord line resulted in a 4 % increase in cloud cavitation shedding frequency and a 5 % reduction in the lift-to-drag ratio. In contrast, implementing the semi-spherical surface microstructures near the trailing edge influenced the re-entrant jet and local pressure distribution, breaking large cavities into smaller ones. This naturally increased the frequency of cavity shedding by 19.4 % while also increasing the lift-to-drag ratio by approximately 2.5 %. The study also analyzes surface-vortex-cavitation interaction using the vorticity transport equation, finding that microstructures enhance vortex stretching while reducing vortex dilatation and baroclinic torque terms. Overall, the findings suggest that microstructures can stabilize cloud cavitation, leading to a more uniform pressure distribution and smoother flow over the hydrofoil.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"188 ","pages":"Article 105206"},"PeriodicalIF":3.6,"publicationDate":"2025-03-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143620183","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":"Characterising slug flow in a horizontal pipe using bubble image velocimetry","authors":"Belma B. Hadzovic ,&nbsp;Eirik Æsøy ,&nbsp;Paul R. Leinan ,&nbsp;James R. Dawson","doi":"10.1016/j.ijmultiphaseflow.2025.105196","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105196","url":null,"abstract":"<div><div>In this paper, we investigate air–water slug flow in a horizontal pipe using bubble image velocimetry (BIV). We show that a good estimate of the ensemble-averaged velocity field can be obtained by tracking the bubbles using a correlation based method, even for highly aerated flows where traditional velocimetry methods such as particle image velocimetry (PIV) are very challenging to implement. The global slug statistics in terms of the translational velocity, slug frequency, and length are compared against measurements from gamma densitometers, showing excellent agreement for a wide range of operating conditions. New insight into the velocity variations of three distinct regions; the slug front, the slug body, and the liquid film, are identified and analysed using BIV. Furthermore, along with the velocity fields, the images were used to obtain an estimate of the bubble density spatial distribution to understand the bubble transport inside the liquid slugs.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"188 ","pages":"Article 105196"},"PeriodicalIF":3.6,"publicationDate":"2025-03-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143620184","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":"Towards quantitative prediction of droplet collision outcomes: A dual-VOF approach with rarefied gas effect and augmented van der Waals force","authors":"Ning Wang ,&nbsp;Zhenyu Zhang ,&nbsp;Peng Zhang ,&nbsp;Changlu Zhao","doi":"10.1016/j.ijmultiphaseflow.2025.105207","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105207","url":null,"abstract":"<div><div>A dual-VOF (volume of fluid) approach incorporating with the adaptive mesh refinement (AMR) algorithm, the rarefied gas effect (RGE), and the augmented van der Waals (vdW) force was proposed and validated in the present study for predicting droplet collision outcomes, particularly the bouncing and coalescence. RGE is introduced by modifying the gas phase viscosity within the gas film, while vdW force is incorporated using a disjoining pressure model. The results show that the present method can successfully predict the non-monotonic trend for head-on collision that collision outcome transfers from soft coalescence to bouncing then to hard coalescence with increasing the Weber number. This trend has been well observed in many previous experimental works. Although the adopted Hamaker constant was substantially augmented compared with the physically realistic one, it is by three orders of magnitude smaller than those adopted by the previous simulation works. The present method is demonstrated to be a small but firm step toward quantitatively predicting droplet collision in gaseous medium, a well-recognized multi-scale, multi-physics problem.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"188 ","pages":"Article 105207"},"PeriodicalIF":3.6,"publicationDate":"2025-03-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143549632","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 analysis of velocity field characteristics within bubble wakes in fiber bundle","authors":"Roberta Fátima Neumeister ,&nbsp;Ryo Kurimoto ,&nbsp;Ryuya Komine ,&nbsp;Gherhardt Ribatski ,&nbsp;Kosuke Hayashi","doi":"10.1016/j.ijmultiphaseflow.2025.105197","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105197","url":null,"abstract":"<div><div>Membrane bioreactors (MBRs) are commonly employed for wastewater treatment, coupling biological processes and filtration. Among the available configurations, vertical fibers are usually applied. The multiphase flow inside the MBR is complex and the relative motion of the bubble, the wall effect, the interaction with fibers, and the main involved phenomena are not fully understood. The present study concerns an analysis of the velocity field within the bubble wake under conditions with (WF) and without (NF) fiber bundle interaction. The experimental setup consisted of 144 fibers in a square tank with a width of 160 mm filled with water where single air bubbles are injected in the central position. The equivalent bubble diameter ranged from 9.85 to 18.7 mm. The velocity fields were measured in the water tank containing silicon carbide (SiC) particles illuminated by a laser sheet through the Spatial Filter Velocimetry (SFV) technique. Particles images were acquired at 37,500 fps and processed to obtain bubbles terminal velocities, wake velocity fields, temporal data series, and bubble-induced turbulence. The velocity field result revealed that under NF conditions bubbles smaller than 13 mm presents a zigzag motion, while for larger bubbles straight upward flow predominated. Under WF conditions, straight upward flow was observed for all evaluated bubbles. Furthermore, the flow field in the WF condition was contained within fibers, forming a like subchannel flow, and showed closed wake characteristics, while the NF condition shows an expanding wake. This reveals a reduction in bubble wake size for the WF condition. Intensity of velocity fluctuation was observed contained within the subchannels for WF conditions, while the affected area for NF was always larger for the tested cases.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"188 ","pages":"Article 105197"},"PeriodicalIF":3.6,"publicationDate":"2025-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143562435","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 simulation of tip vortex cavitation using a multiscale method","authors":"Xinzhen Qin ,&nbsp;Ben Zhang ,&nbsp;Yang Li ,&nbsp;Yuqi Huang ,&nbsp;Xueming Shao ,&nbsp;Jian Deng","doi":"10.1016/j.ijmultiphaseflow.2025.105183","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105183","url":null,"abstract":"<div><div>We propose a multiscale Euler–Lagrange method to simulate tip vortex cavitation (TVC), accurately modelling bubble dynamics at the macroscopic Eulerian scale. The method employs mapping strategies using a Gaussian kernel function and topological relationships to represent momentum and mass transfer between the Eulerian and Lagrangian frames. We investigate the effects of nuclei content and spatial distribution on TVC inception induced by an elliptical foil, comparing the predicted cavitation inception indices with experimental data, wetted flow simulations, and conventional Euler cavitation simulations. Our results demonstrate that the model yields cavitation inception indices that closely align with experimental observations. Additionally, our simulations reveal a direct correlation between the index and location of TVC inception with both the content and spatial distribution of nuclei. We also examine the temporal evolution of a single nucleus injected at the same position under different cavitation numbers to elucidate the mechanism of TVC inception. We observe two distinct outcomes for nucleus evolution. At higher ambient pressures, only localised elongated cavities move downstream and eventually collapse, a phenomenon not captured by traditional Euler simulations or hybrid Euler–Lagrange methods. When pressure is sufficiently low, a nucleus captured downstream of the minimum pressure location can progress upstream and trigger sustained TVC by connecting to the downstream cavity. This research offers a promising methodology for a deeper understanding of TVC inception and highlights the significant role of nuclei in this process.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"188 ","pages":"Article 105183"},"PeriodicalIF":3.6,"publicationDate":"2025-02-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143520804","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":"Single-plume and multi-plume atomisation of ethanol with different levels of water content at hot fuel conditions","authors":"P.G. Aleiferis ,&nbsp;J. Shukla ,&nbsp;M. Brewer ,&nbsp;R.F. Cracknell","doi":"10.1016/j.ijmultiphaseflow.2025.105199","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105199","url":null,"abstract":"<div><div>Producing anhydrous ethanol involves separation of ethanol and water in an energy intensive process. It is possible to use ethanol (without any gasoline) as a fuel in countries where the ambient temperature is high enough that the low vapour pressure of pure ethanol does not give rise to significant cold weather driveability issues. From a cost and carbon footprint perspective, it is highly desirable to use hydrous ethanol, but there is a clear need to understand the effect of water content in ethanol on the spray formation process and hence mixture formation. The present paper presents results from an optical experimental investigation into the effects of 0–15 % water content per volume in ethanol on spray formation, using high-speed imaging and droplet sizing. Experiments were carried out with fuel temperatures in the range 20–110 °C at 1.0 bar and 0.5 bar gas pressure. <em>Iso</em>-octane and water were also tested for comparison. Multi-hole and isolated single-hole injections were studied to decouple effects from plume-to-plume interactions. Single-plume hydrous ethanol fuels showed initial delay out of the nozzle with shorter penetration but gradually achieved or surpassed the liquid penetration of the anhydrous fuel. Increased water content was generally associated with reduced single plume cone angle between 20 and 90 °C, but at 110 °C the order was reversed, with the hydrous ethanol blends having greater cone angle than the anhydrous which has implications for spray collapse upon multi-plume operation. At 20 °C, 1.0 bar, anhydrous ethanol showed larger droplets than <em>iso</em>-octane by ∼5 %, with the addition of 10 % water increasing the SMD by about a further 5 %. Water showed larger SMD than the fuels by 30–40 %. At 110 °C, 0.5 bar, all fuels showed smaller droplets by 20–30 % than at the subcooled condition. When comparing the isolated single-plume spray with the respective plume pair of the multi-hole experiment for anhydrous ethanol and <em>iso</em>-octane at subcooled conditions, it was observed that the plume pair had higher penetration. This could be attributed to near-nozzle effects from interacting adjacent plumes, differences in gas entrainment and drag. At superheated conditions, the penetration of the multi-hole plume pair for <em>iso</em>-octane was similar to that of the isolated single-hole plume spray. However, for ethanol it was clearly shorter due to presence of plume merging and initiation of spray collapse, effects that were absent for the single-plume configuration. The fact that increasing water content was associated with wider near-nozzle plume angle at superheated conditions and stronger propensity for plume merging and spray collapse, despite the slightly lower vapour pressure, suggests that other effects, <em>e.</em>g<em>.</em> related to the higher heat capacity of water and potential temperature saturation upon phase change, could dominate the process.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"188 ","pages":"Article 105199"},"PeriodicalIF":3.6,"publicationDate":"2025-02-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143549567","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}