International Journal of Multiphase Flow最新文献

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Liquid evaporation from nanochannel with rough wall surface by direct simulation Monte Carlo 采用蒙特卡罗直接模拟方法对粗糙壁纳米通道中液体蒸发进行了研究
IF 3.6 2区 工程技术
International Journal of Multiphase Flow Pub Date : 2025-07-02 DOI: 10.1016/j.ijmultiphaseflow.2025.105352
Ran Li, Ziqing Yan, Xiupeng Cheng, Yinuo Wang, Guodong Xia
{"title":"Liquid evaporation from nanochannel with rough wall surface by direct simulation Monte Carlo","authors":"Ran Li,&nbsp;Ziqing Yan,&nbsp;Xiupeng Cheng,&nbsp;Yinuo Wang,&nbsp;Guodong Xia","doi":"10.1016/j.ijmultiphaseflow.2025.105352","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105352","url":null,"abstract":"<div><div>Roughness in nanoscale channels has profound influences on liquid flow and evaporation from the channel which is relevant in many cutting-edge applications. The direct simulation Monte Carlo (DSMC) method was employed to numerically study the effects of roughness shape, size and interval distance on the liquid evaporation rate from a nanochannel. It was found that the inclination angle of roughness elements plays a vital role in determining the liquid evaporation resistance of nanochannel. Under sparse roughness condition, the rectangle roughness with larger inclination angle leads to higher evaporation resistance. Under dense roughness condition, the vapor was inhibited from entering the gap between rectangle roughness and the velocity sink effect was weakened. The evaporation resistance for rectangle roughness declined as the roughness interval continued to reduce, while triangle and semicircle roughness with smaller inclination angle could retain the increase of evaporation resistance. Larger roughness size leads to higher evaporation resistance for the three roughness shapes. A phenomenological model was proposed to correlate the computed evaporation resistance; the model accounted for roughness inclination angle and had different behaviors under sparse and dense roughness conditions. The evaporation resistance was well correlated to the newly defined model with error being around ± 5 %.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"192 ","pages":"Article 105352"},"PeriodicalIF":3.6,"publicationDate":"2025-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144557316","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}
引用次数: 0
Mixing in axially rotating co-laminar flows 轴向旋转共层流中的混合
IF 3.6 2区 工程技术
International Journal of Multiphase Flow Pub Date : 2025-07-02 DOI: 10.1016/j.ijmultiphaseflow.2025.105351
Pooyan Heravi , Li-An Chu , Da-Jeng Yao
{"title":"Mixing in axially rotating co-laminar flows","authors":"Pooyan Heravi ,&nbsp;Li-An Chu ,&nbsp;Da-Jeng Yao","doi":"10.1016/j.ijmultiphaseflow.2025.105351","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105351","url":null,"abstract":"<div><div>We investigate how Diffusion-Induced Lateral Flow (DILF) alters mixing in straight microchannels, a fundamental yet under-explored microfluidic configuration. By employing a spinning disk confocal microscope and finite element numerical simulations, the study provides an in-depth analysis of mixing in co-laminar sucrose/urea streams. Results show that even in density-matched supplies, DILF generates measurable secondary vortices that broaden the interdiffusion zone and raise the cross-section-averaged mixing. Mixing enhancement is most pronounced at intermediate velocities (0.1–0.3 cm s⁻¹) and in channels with aspect ratios &gt; 1, where interface elongation amplifies diffusion. These insights refine design rules for microfluidic assays that rely on either suppressing or exploiting controlled mixing, and lay groundwork for empirical DILF-based mixer models, geometry optimization, and future sheath-flow studies.</div><div>The results presented have the potential to significantly improve the accuracy of spatially resolved surface chemistry and biology in microfluidics, thereby advancing microfluidic technology and its applications across various industries.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"192 ","pages":"Article 105351"},"PeriodicalIF":3.6,"publicationDate":"2025-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144656719","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}
引用次数: 0
Slug-to-churn or churn-to-slug: revisiting the flow patterns transition debate 段塞到搅动或搅动到段塞:重新审视流动模式转换的争论
IF 3.6 2区 工程技术
International Journal of Multiphase Flow Pub Date : 2025-07-01 DOI: 10.1016/j.ijmultiphaseflow.2025.105350
Shahriyar G. Holagh, Wael H. Ahmed
{"title":"Slug-to-churn or churn-to-slug: revisiting the flow patterns transition debate","authors":"Shahriyar G. Holagh,&nbsp;Wael H. Ahmed","doi":"10.1016/j.ijmultiphaseflow.2025.105350","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105350","url":null,"abstract":"<div><div>Perhaps one of the most contentious yet long-lasting debates in slug and churn flow literature revolves around the directional nature of the transition between these two flow patterns. Which terminology truly captures its nature—slug-to-churn or churn-to-slug transition? The present study is tackling this debate through an experimental investigation by leveraging high-speed flow visualization and a synergistic combination of advanced signal processing techniques. The analysis is performed for void fraction waves recorded at Z/<em>D</em> = 10, 25, 40, and 60 in an air-water flow along a vertical pipe under gravity-driven conditions at an elevated inlet superficial gas velocity. Visual insights from high-speed imaging conducted at the same spatial positions, combined with statistical analysis and a spatiotemporal-spectral framework incorporating Recurrence Quantification Analysis (RQA), Power Spectral Density (PSD), and Direct and Continuous Wavelet Transforms (DWT and CWT), provided a multidimensional, cross-validated approach—both qualitative and quantitative—to conclusively determine the transition mechanisms and direction. The findings establish churn flow as a spatial precursor to slug flow, unfolding through four distinct regimes: semi-annular, churn, churn-slug transition, and unstable slug flow at Z/<em>D</em> = 10, 25, 40, and 60, correspondingly. The churn-slug transition emerged as a gradual process, wherein diminishing phase interaction-induced instabilities allow slug flow characteristics to take hold. A previously unnoticed mechanism, termed liquid phase penetration, was uncovered as a fundamental driver of churn flow. Propelled by momentum transfer from incoming gas plugs, this mechanism destabilizes leading gas plugs, amplifies huge wave formation, and reinforces flooding dynamics, propagating churning behaviour in upward direction. Its role is pivotal, making its incorporation into slug/churn transition models—especially those based on the entrance effect theory—imperative. Moreover, the study confirmed the exceptional performance (∼99.85 % accuracy) of a novel AI-based diagnostic tool, integrating the CWT framework with a CNN, offering a real-time, scale-independent data-driven solution for axial flow pattern identification (i.e., static instability diagnosis), promising enhanced operational reliability and safety in systems of varying dimensions operating under developing two-phase flow conditions. Nonetheless, this study offers a preliminary contribution, aiming to ignite discussion, encourage future endeavours, and shape the trajectory of future investigations into the slug/churn transition. To solidify the present findings, further experimentation in long pipes and across a broad range of inlet superficial gas velocities is essential.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"192 ","pages":"Article 105350"},"PeriodicalIF":3.6,"publicationDate":"2025-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144548404","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}
引用次数: 0
Numerical investigation of particle transport and deposition mechanisms driven by multiphase explosion coupling with buffer gas stream 多相爆炸耦合缓冲气流驱动下颗粒输运沉积机理的数值研究
IF 3.6 2区 工程技术
International Journal of Multiphase Flow Pub Date : 2025-06-30 DOI: 10.1016/j.ijmultiphaseflow.2025.105336
Leqi Liu , Baoqing Meng , Honghui Teng , Baolin Tian
{"title":"Numerical investigation of particle transport and deposition mechanisms driven by multiphase explosion coupling with buffer gas stream","authors":"Leqi Liu ,&nbsp;Baoqing Meng ,&nbsp;Honghui Teng ,&nbsp;Baolin Tian","doi":"10.1016/j.ijmultiphaseflow.2025.105336","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105336","url":null,"abstract":"<div><div>Debris suppression and expulsion are among the key challenges in designing and optimizing the light source system of extreme ultraviolet lithography (EUVL). The mechanisms of debris transport and deposition still require further investigation. The study of this problem involves compressible gas-particle multiphase fluid dynamics. In this study, the transport, spatial distribution characteristics of debris particles, and the wall deposition mechanism within a rectangular cavity are investigated from the multiphase flow perspective by employing the compressible multiphase particle-in-cell (CMP-PIC) method. Our analysis reveals that particle transport encompasses the following processes: Firstly, multiple particle jets are induced due to shock-driven multiphase instability. Subsequently, the bending and coalescing process of particle jets are observed under the influence of vortex and buffer gas stream. Simultaneously, particles aggregate near the explosion center and are transported by the buffer gas stream. Furthermore, three distinct deposition mechanisms are identified for the first time, namely: (1) velocity-induced separation within the particle-buffer gas stream, (2) high-velocity particle jet impact, and (3) particle cluster transport driven by the buffer gas stream. Additionally, parametric study was conducted to evaluate the effect of particle diameter on the debris transport and deposition mechanism. Owing to variations of inertia and relaxation time, significant differences in the evolution, position distribution, and coalescing process are observed, which subsequently affect the deposition momentum of each wall and the emission ratio. Results indicate that smaller particles (<em>d<sub>p</sub></em>=0.2 μm and <em>d<sub>p</sub></em>=0.6 μm) exhibit shorter relaxation times, leading to enhanced expulsion by the buffer gas stream and reduced wall deposition momentum. Whereas larger particles (<em>d<sub>p</sub></em>=1.0 μm and <em>d<sub>p</sub></em>=2.0 μm) lag in evolution, weaken particle jet coalescing process, and increase wall deposition momentum due to its large inertia. Three-dimensional simulation results show that particle-buffer gas stream velocity separation and high-velocity particle impact mechanisms dominate particle distribution, while the influence of particle cluster formation and transport is significantly diminished. These findings on transport characteristics and deposition mechanism of particles provide valuable insights for optimizing EUVL source system.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"192 ","pages":"Article 105336"},"PeriodicalIF":3.6,"publicationDate":"2025-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144563887","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}
引用次数: 0
Inhibition of cloud cavitation with actively controlled flexible surface driven by piezoelectric actuator 压电驱动器主动控制柔性表面对云空化的抑制
IF 3.6 2区 工程技术
International Journal of Multiphase Flow Pub Date : 2025-06-30 DOI: 10.1016/j.ijmultiphaseflow.2025.105347
Wei Wang, Shuai Liu, Yegao Qu, Penglin Gao, Zhike Peng
{"title":"Inhibition of cloud cavitation with actively controlled flexible surface driven by piezoelectric actuator","authors":"Wei Wang,&nbsp;Shuai Liu,&nbsp;Yegao Qu,&nbsp;Penglin Gao,&nbsp;Zhike Peng","doi":"10.1016/j.ijmultiphaseflow.2025.105347","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105347","url":null,"abstract":"<div><div>Cloud cavitation in hydraulic machines can lead to severe vibration, noise, and surface damage, ultimately degrading performance. To address this issue, this study investigates the mitigation effects of an actively controlled flexible surface on typical cloud cavitating flow over a hydrofoil. A two-way fluid-structure interaction computational model is developed by coupling the unsteady Reynolds-averaged Navier–Stokes equations with structural dynamic equations. Flexible surfaces driven by piezoelectric actuators with different actuation frequencies and amplitudes are strategically arranged at three representative regions along the hydrofoil. Results demonstrate that high-frequency and high-amplitude actuation effectively mitigates cloud cavitation phenomena. Notably, large-scale cavity shedding from the upstream region transitions into small-scale cavity shedding in the closure region. The presence of flexible surfaces enhances the thickness of the re-entrant jet while reducing its velocity, thereby diminishing its ability to pinch off the cavity. Fourier analysis reveals that fluctuations in vapor fraction at the actuation frequency predominate in the shear layer, propagating from the leading edge of the cavity to its wake. Furthermore, a one-dimensional model indicates that pressure fluctuations throughout the domain arise from the volume changes induced by the flexible surface, positively correlating with the second time derivative of the resultant volume. Consequently, it is concluded that flexible surfaces actuated by piezoelectric patches serve as an effective method for mitigating cloud cavitation.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"192 ","pages":"Article 105347"},"PeriodicalIF":3.6,"publicationDate":"2025-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144588183","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}
引用次数: 0
Enhanced modeling for resolved morphologies in co-current stratified wavy pipe flows 加强了共流分层波浪管流中分解形态的建模
IF 3.6 2区 工程技术
International Journal of Multiphase Flow Pub Date : 2025-06-29 DOI: 10.1016/j.ijmultiphaseflow.2025.105333
Michele Cristina Pedroso , Josiane Weise , Richard Meller , Fabian Schlegel , Rafael Franklin Lázaro de Cerqueira , Emilio Ernesto Paladino
{"title":"Enhanced modeling for resolved morphologies in co-current stratified wavy pipe flows","authors":"Michele Cristina Pedroso ,&nbsp;Josiane Weise ,&nbsp;Richard Meller ,&nbsp;Fabian Schlegel ,&nbsp;Rafael Franklin Lázaro de Cerqueira ,&nbsp;Emilio Ernesto Paladino","doi":"10.1016/j.ijmultiphaseflow.2025.105333","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105333","url":null,"abstract":"<div><div>This paper presents the development and validation of a model for simulating stratified flows with wavy interfaces within the two-fluid framework. A key focus is the interfacial momentum transfer closure for large-scale interfaces (LSIs), which is critical for Euler–Euler multiphase flow simulations involving distinct phase morphologies. A systematic evaluation of existing momentum transfer models for resolved morphologies, including those by Strubelj &amp; Tiselj, Marschall, and a blended approach, is conducted alongside the proposition of a new Modified Mixture Model (MMM) for LSIs. The numerical simulations are compared against experimental data from the literature, revealing the limitations of traditional closure models for wavy flows and the impact of limited volume fraction on interfacial momentum transfer and wave growth. A novel diffusive stabilization approach is proposed, removing the inconsistencies introduced by limited phase-volume fraction in the momentum transfer modeling. The MMM model demonstrates robustness across mesh refinements, effectively capturing wave dynamics, mean water height, pressure drop, and key wave characteristics. The study also highlights the importance of turbulence damping, which increases the velocity gradients at the interface, contributing to phase decoupling and facilitating wave growth. These findings establish the MMM model as a reasonable approach for simulating stratified wavy flows.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"192 ","pages":"Article 105333"},"PeriodicalIF":3.6,"publicationDate":"2025-06-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144597311","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}
引用次数: 0
Dynamic characteristics of thin vapor layers at substrate temperatures below the Leidenfrost point 衬底温度低于莱顿弗罗斯特点时薄气相层的动态特性
IF 3.6 2区 工程技术
International Journal of Multiphase Flow Pub Date : 2025-06-28 DOI: 10.1016/j.ijmultiphaseflow.2025.105332
Ken Yamamoto , Keigo Katayama , Yutaku Kita
{"title":"Dynamic characteristics of thin vapor layers at substrate temperatures below the Leidenfrost point","authors":"Ken Yamamoto ,&nbsp;Keigo Katayama ,&nbsp;Yutaku Kita","doi":"10.1016/j.ijmultiphaseflow.2025.105332","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105332","url":null,"abstract":"<div><div>Volatile drops can levitate on hot substrates by forming a thin vapor layer beneath them. The minimum temperature for stable vapor layer formation is called the Leidenfrost point, but the transition mechanism remains unclear. To investigate this, we studied the liquid–solid contact of Leidenfrost drops below the Leidenfrost point. Steady-state, pancake-like water drops were generated by sandwiching water between a hot substrate and a glass capillary, forming nearly flat vapor films while maintaining constant volume. Vapor film shapes (with thicknesses on the order of <span><math><mrow><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mn>0</mn></mrow></msup></mrow></math></span> <span><math><mrow><mi>μ</mi><mi>m</mi></mrow></math></span>, confirmed experimentally and by a heat conduction model) were observed by interferometry. Although the films were generally stable for several minutes, microscopic perturbations consistently appeared and stochastic, sudden liquid–solid contacts, likely induced by van der Waals interactions, occurred at a peak of the perturbations. The selection rules for the wavelength and amplitude of the perturbation (measured as <span><math><mo>∼</mo></math></span>300–400 <span><math><mrow><mi>μ</mi><mi>m</mi></mrow></math></span> and <span><math><mo>∼</mo></math></span>2 <span><math><mrow><mi>μ</mi><mi>m</mi></mrow></math></span>, respectively) were revealed by scaling analysis, derived from the balance between the vapor flow pressure drop and local Laplace pressure. Because the wavelength and amplitude were nearly insensitive to substrate temperature for a given drop radius, liquid–solid contact likely occurs when the vapor thickness approaches the perturbation amplitude. The liquid–solid contact is then driven by the natural resonance of the drops, which induces van der Waals interactions. Additionally, the effects of high (sapphire) and low (quartz) conductivity substrates were examined using an unsteady heat-conduction model, revealing that low-conductivity substrates exhibit larger local cooling, potentially promoting contact events.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"191 ","pages":"Article 105332"},"PeriodicalIF":3.6,"publicationDate":"2025-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144522081","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}
引用次数: 0
An experimental and numerical investigation to study slug characteristics in miniature geometries 微型几何形状中段塞特性的实验与数值研究
IF 3.6 2区 工程技术
International Journal of Multiphase Flow Pub Date : 2025-06-28 DOI: 10.1016/j.ijmultiphaseflow.2025.105342
Pushpender Chaudhary, Sumana Ghosh
{"title":"An experimental and numerical investigation to study slug characteristics in miniature geometries","authors":"Pushpender Chaudhary,&nbsp;Sumana Ghosh","doi":"10.1016/j.ijmultiphaseflow.2025.105342","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105342","url":null,"abstract":"<div><div>This research presents the prediction of slug length in liquid-liquid two-phase flow using a straight mini capillary of an inner diameter of 2 mm. The study focused on understanding the effects of flow dynamics and thermophysical properties on slug characteristics. Three different combinations of glycerol in distilled water (v/v%) are used to vary the thermophysical properties of the continuous phase. While toluene is used as the dispersed phase. Droplet flow and slug flow are observed as the main flow patterns. The slug length is found to have a proportional relationship with the Reynolds number of the disperse phase while inversed relationship with the Reynolds number of the continuous phase. At a constant Reynolds number of the disperse phase, the specific interfacial area steadily declined with the Reynolds number of the continuous phase. A criterion is proposed for the transition of flow patterns in the form of dimensionless numbers. Further, numerical simulations are performed to understand flow physics at different thermophysical properties using the open software OpenFoam. The inner circulation inside the slug is observed to increase with a decrease in the glycerol content in the continuous phase. Based on experimental data, an artificial neural network model is developed to predict slug length. The results showed that the model successfully establishes the relation between the thermophysical properties of fluids, wall wettability of channel, and slug length. Further, the model is validated with the previously published data and present simulation, showing high accuracy.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"191 ","pages":"Article 105342"},"PeriodicalIF":3.6,"publicationDate":"2025-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144522082","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}
引用次数: 0
Impact of wall-normal external force on particle collision dynamics in turbulent channel flow 紊流通道中壁法向外力对颗粒碰撞动力学的影响
IF 3.6 2区 工程技术
International Journal of Multiphase Flow Pub Date : 2025-06-27 DOI: 10.1016/j.ijmultiphaseflow.2025.105344
Pinzhuo Chen, Sheng Chen, Jianhong Fu, Mingyu Liu
{"title":"Impact of wall-normal external force on particle collision dynamics in turbulent channel flow","authors":"Pinzhuo Chen,&nbsp;Sheng Chen,&nbsp;Jianhong Fu,&nbsp;Mingyu Liu","doi":"10.1016/j.ijmultiphaseflow.2025.105344","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105344","url":null,"abstract":"<div><div>Particle collision in turbulent channel flow is systematically investigated by a direct numerical simulation coupled with Lagrangian particle tracking. For particles with low inertia (characterized by a viscous Stokes number St<sup>+</sup>≤5), the external force slightly reduces the particle clustering, while it promotes the radial relative velocity (RRV). The competition between these two mechanisms results in the collision kernel of low-inertia particles being largely unaffected by the wall-normal external force. For heavy particles with St<sup>+</sup>≥15, a significant reduction in the collision kernel was observed when subjected to the external force. This inhibitory effect increased with the magnitude of the external force <em>ψ</em> and the particle inertia. The radial distribution functions (RDF) of heavy particles display a monotonic decrease with the external force, as the force weakens the interaction between particles and the coherent flow structures. Notably, the RRV of heavy particles exhibits a novel increasing-decreasing trend with the external force. By analyzing the flow structures at the location of colliding particles, we demonstrate that the external force causes faster particles to enter ejection structures, where they collide with slower particles, resulting in an elevation of the relative colliding velocity. Finally, we quantify the contributions of RDF and RRV to the variation of the collision kernel as the external force increased for light and heavy particles.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"192 ","pages":"Article 105344"},"PeriodicalIF":3.6,"publicationDate":"2025-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144580656","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}
引用次数: 0
Numerical study on the scale effect of tip vortex cavitation with special emphasis on non-condensable nuclei 尖端涡空化尺度效应的数值研究,特别强调了不可冷凝核
IF 3.6 2区 工程技术
International Journal of Multiphase Flow Pub Date : 2025-06-27 DOI: 10.1016/j.ijmultiphaseflow.2025.105346
Mohan Xu , Huaiyu Cheng , Bin Ji , Xiaoxing Peng , Cheng Liu
{"title":"Numerical study on the scale effect of tip vortex cavitation with special emphasis on non-condensable nuclei","authors":"Mohan Xu ,&nbsp;Huaiyu Cheng ,&nbsp;Bin Ji ,&nbsp;Xiaoxing Peng ,&nbsp;Cheng Liu","doi":"10.1016/j.ijmultiphaseflow.2025.105346","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105346","url":null,"abstract":"<div><div>Tip vortex cavitation (TVC) around a family of elliptic NACA66<sub>2</sub>–415 hydrofoils with different scales (<em>λ</em>=0.5, 0.75, 1) under the same cavitation number is simulated to study its scale effect. A satisfying agreement is obtained between the numerical and experimental results. Our results suggest that although TVC varies with scales without considering the influence of non-condensable nuclei, that difference is much more significant when nuclei effect is considered in the simulations. Moreover, it indicates that nuclei influence is more significant for a larger scale. It strongly proves the important role of nuclei in TVC scale effect. By comparing the pressure gradients in various directions, it is found that the pressure gradient in the radial direction leads to the enrichment of nuclei in the tip vortex core. With the increase of scale, the radial pressure gradient increases, which further causes the increase of nuclei concentration. In addition, a practical method for predicting nuclei concentration in the tip vortex core is proposed. The theoretical derivation indicates the proportionality between the dimensionless nuclei concentration in the tip vortex core and the dimensionless circulation, which is validated by the numerical results. A fitting equation between dimensionless nuclei concentration and tip vortex circulation is then provided, by which the nuclei concentration can be forecast without the time-consuming simulation of nuclei movement.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"192 ","pages":"Article 105346"},"PeriodicalIF":3.6,"publicationDate":"2025-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144534701","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}
引用次数: 0
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