Pub Date : 2024-10-18DOI: 10.1016/j.ijmultiphaseflow.2024.105032
Zhongxin Liu , Xuan Zhang , Mengjie Song , Long Zhang , Yubo Gao , Han Shi , Yonghui Liang
The anti-/de-icing capability of ships and offshore structures in the polar regions is of importance to ensure the safety of operation. The bubble anti-/de-icing method has great application potential. Here, a point-source bubbler system is developed to study the ice melting processes under point-source bubble flows, especially ice melting stage, bubble distribution, ice melting rate, and final ice morphology. The ice melting process is divided into flat, concave, and holed ice stages. With the increase of the flow rate, the duration of the ice melting process gradually decreases while that of the flat ice stage increases and that of the concave ice stage decreases. The number density of bubbles at the concave ice stage is the smallest and the average contact area of bubbles at the concave ice stag is the largest of the three stages. The average contact areas of bubbles at 1.0 L/min and 1.5 L/min are significantly larger than those at 0.5 L/min and 2.0 L/min at the concave ice stage. When the flow rate increases from 0.5 L/min to 2.0 L/min, the melting rate in the height direction increases by 95.4 % while the melting rate in the radial direction increases by 61.8 %. The cross-sectional profile of the final ice morphology gradually becomes steeper as the flow rate rises. The findings of this work provide insights into the ice melting mechanism under bubble flows and are helpful to the optimization of related applications.
{"title":"An experimental study on ice melting processes under point-source bubble flows at different flow rates","authors":"Zhongxin Liu , Xuan Zhang , Mengjie Song , Long Zhang , Yubo Gao , Han Shi , Yonghui Liang","doi":"10.1016/j.ijmultiphaseflow.2024.105032","DOIUrl":"10.1016/j.ijmultiphaseflow.2024.105032","url":null,"abstract":"<div><div>The anti-/de-icing capability of ships and offshore structures in the polar regions is of importance to ensure the safety of operation. The bubble anti-/de-icing method has great application potential. Here, a point-source bubbler system is developed to study the ice melting processes under point-source bubble flows, especially ice melting stage, bubble distribution, ice melting rate, and final ice morphology. The ice melting process is divided into flat, concave, and holed ice stages. With the increase of the flow rate, the duration of the ice melting process gradually decreases while that of the flat ice stage increases and that of the concave ice stage decreases. The number density of bubbles at the concave ice stage is the smallest and the average contact area of bubbles at the concave ice stag is the largest of the three stages. The average contact areas of bubbles at 1.0 L/min and 1.5 L/min are significantly larger than those at 0.5 L/min and 2.0 L/min at the concave ice stage. When the flow rate increases from 0.5 L/min to 2.0 L/min, the melting rate in the height direction increases by 95.4 % while the melting rate in the radial direction increases by 61.8 %. The cross-sectional profile of the final ice morphology gradually becomes steeper as the flow rate rises. The findings of this work provide insights into the ice melting mechanism under bubble flows and are helpful to the optimization of related applications.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"182 ","pages":"Article 105032"},"PeriodicalIF":3.6,"publicationDate":"2024-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142554488","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-18DOI: 10.1016/j.ijmultiphaseflow.2024.105031
Xu Yan , Yao Xiao , Xiaowen Wang , Junlong Li , Hanyang Gu
This study investigated the axial two-phase flow evolution and interfacial area transport characteristics downstream of the mixing vane spacer grid (MVSG) in a tight lattice rod bundle channel with a subchannel hydraulic diameter of Dh = 17.27 mm. The experiment was conducted under the air-water two-phase flow at room temperature and atmospheric pressure. The phase distributions of 6 positions downstream of MVSG (Z/Dh = 9.15, 14.94, 20.73, 26.52, 32.31, and 61.26) were measured utilizing a self-developed double-layer wire-mesh sensor (WMS). 42 cases were obtained, involving the bubbly flow, cap-bubbly flow, and slug flow. Void fraction, bubble velocity, interfacial area concentration (IAC), and bubble size distribution (BSD) databases were built. Under the group-1 (G-1) flow, due to the swirling flow generated by MVSG, the G-1 bubbles were drawn from the bundle surface and the gap region into the subchannel center to form a spindle core-peak distribution. BSD results demonstrate that the swirling flow promotes bubbles’ coalescence. The one-dimensional (1-D) void fraction and IAC downstream of the MVSG decrease first and then recover, which contrasts with the non-mixing vane spacer grid (N-MVSG) effect. It was attributed to the increment of the bubbles’ velocity after MVSG due to the bubbles’ migration to the channel center and coalescence. Under the group-2 (G-2) flow, MVSG intensifies the core peak distribution of void fraction, and the void fraction profile is also spindle-shaped. The obvious bubbles’ break-up occurs at Z/Dh = 14.94 attributed to the swirling decay. The 1-D void fraction and IAC transport indicate, that with the liquid-velocity increment, the MVSG effect is different from the N-MVSG effect, which is mainly achieved by affecting the G-1 bubbles’ dynamic behaviors. The model evaluation utilizing the interfacial area transport equation (IATE) closing bubble interaction source/sink terms indicates that the advection effect dominates the IAC evolution and the contribution of the pressure effect is weak. The remarkable bubbles’ coalescence occurs under the high liquid velocity. In future studies, the additional bubble break-up and coalescence source/sink term model considering the MVSG effect should be developed based on these cases to improve the IATE prediction ability.
{"title":"Two-phase flow evolution and interfacial area transport downstream of the mixing-vane spacer grid in rod bundle channels","authors":"Xu Yan , Yao Xiao , Xiaowen Wang , Junlong Li , Hanyang Gu","doi":"10.1016/j.ijmultiphaseflow.2024.105031","DOIUrl":"10.1016/j.ijmultiphaseflow.2024.105031","url":null,"abstract":"<div><div>This study investigated the axial two-phase flow evolution and interfacial area transport characteristics downstream of the mixing vane spacer grid (MVSG) in a tight lattice rod bundle channel with a subchannel hydraulic diameter of <em>D</em><sub>h</sub> = 17.27 mm. The experiment was conducted under the air-water two-phase flow at room temperature and atmospheric pressure. The phase distributions of 6 positions downstream of MVSG (<em>Z</em>/<em>D</em><sub>h</sub> = 9.15, 14.94, 20.73, 26.52, 32.31, and 61.26) were measured utilizing a self-developed double-layer wire-mesh sensor (WMS). 42 cases were obtained, involving the bubbly flow, cap-bubbly flow, and slug flow. Void fraction, bubble velocity, interfacial area concentration (IAC), and bubble size distribution (BSD) databases were built. Under the group-1 (G-1) flow, due to the swirling flow generated by MVSG, the G-1 bubbles were drawn from the bundle surface and the gap region into the subchannel center to form a spindle core-peak distribution. BSD results demonstrate that the swirling flow promotes bubbles’ coalescence. The one-dimensional (1-D) void fraction and IAC downstream of the MVSG decrease first and then recover, which contrasts with the non-mixing vane spacer grid (N-MVSG) effect. It was attributed to the increment of the bubbles’ velocity after MVSG due to the bubbles’ migration to the channel center and coalescence. Under the group-2 (G-2) flow, MVSG intensifies the core peak distribution of void fraction, and the void fraction profile is also spindle-shaped. The obvious bubbles’ break-up occurs at <em>Z</em>/<em>D</em><sub>h</sub> = 14.94 attributed to the swirling decay. The 1-D void fraction and IAC transport indicate, that with the liquid-velocity increment, the MVSG effect is different from the N-MVSG effect, which is mainly achieved by affecting the G-1 bubbles’ dynamic behaviors. The model evaluation utilizing the interfacial area transport equation (IATE) closing bubble interaction source/sink terms indicates that the advection effect dominates the IAC evolution and the contribution of the pressure effect is weak. The remarkable bubbles’ coalescence occurs under the high liquid velocity. In future studies, the additional bubble break-up and coalescence source/sink term model considering the MVSG effect should be developed based on these cases to improve the IATE prediction ability.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"182 ","pages":"Article 105031"},"PeriodicalIF":3.6,"publicationDate":"2024-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142572452","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-18DOI: 10.1016/j.ijmultiphaseflow.2024.105033
S.J. Neethling, J.E. Avalos-Patiño, P.R. Brito-Parada, D. Mesa
Particle–laden flows occur in many natural and industrial systems and simulating them can be particularly challenging. The coupling of smoothed particle hydrodynamics (SPH) with the discrete element method (DEM) can effectively simulate particle-laden multiphase fluid dynamical systems, due to the shared Lagrangian nature of both methods. However, this approach has some inherent shortcomings, including a prohibitively small time step when dealing with small particles. An alternative approach is to use an Eulerian-Eulerian reference frame, usually using finite element or finite volume discretisations. In this approach, momentum and continuity equations are solved for each discrete phase as well as the continuous phase, and particles are modelled by means of concentration and velocity fields. This approach can suffer from strong numerical diffusion in the advection of the concentrations when absolute velocities of the phases are high, whilst their relative velocities are small. This numerical diffusion can obscure important aspects of the behaviour as it can smooth out details, especially in the particle concentration fields. In order to mitigate the shortcomings of these existing techniques, we present a new SPH-based semi-Lagrangian framework for solving the momentum and continuity equations for all phases in particle-laden flows. In this framework, the discrete and continuous phases move relative to a reference frame that moves at a momentum-averaged velocity. By focusing on velocities relative to the reference frame our method substantially reduces numerical diffusion compared to traditional Eulerian-Eulerian approaches, at a lower computational cost compared to Lagrangian-Lagrangian approaches. The simulation approach is validated by means of comparisons to both computational and experimental results for a number of relevant systems including particle-liquid separation in an inclined channel, particle sedimentation in a liquid, and gas-particle fluidised beds. This new method is shown to compare very favourably in terms of both the accuracy of the results and the computational cost required to achieve them.
{"title":"Semi-Lagrangian simulation of particle laden flows using an SPH framework","authors":"S.J. Neethling, J.E. Avalos-Patiño, P.R. Brito-Parada, D. Mesa","doi":"10.1016/j.ijmultiphaseflow.2024.105033","DOIUrl":"10.1016/j.ijmultiphaseflow.2024.105033","url":null,"abstract":"<div><div>Particle–laden flows occur in many natural and industrial systems and simulating them can be particularly challenging. The coupling of smoothed particle hydrodynamics (SPH) with the discrete element method (DEM) can effectively simulate particle-laden multiphase fluid dynamical systems, due to the shared Lagrangian nature of both methods. However, this approach has some inherent shortcomings, including a prohibitively small time step when dealing with small particles. An alternative approach is to use an Eulerian-Eulerian reference frame, usually using finite element or finite volume discretisations. In this approach, momentum and continuity equations are solved for each discrete phase as well as the continuous phase, and particles are modelled by means of concentration and velocity fields. This approach can suffer from strong numerical diffusion in the advection of the concentrations when absolute velocities of the phases are high, whilst their relative velocities are small. This numerical diffusion can obscure important aspects of the behaviour as it can smooth out details, especially in the particle concentration fields. In order to mitigate the shortcomings of these existing techniques, we present a new SPH-based semi-Lagrangian framework for solving the momentum and continuity equations for all phases in particle-laden flows. In this framework, the discrete and continuous phases move relative to a reference frame that moves at a momentum-averaged velocity. By focusing on velocities relative to the reference frame our method substantially reduces numerical diffusion compared to traditional Eulerian-Eulerian approaches, at a lower computational cost compared to Lagrangian-Lagrangian approaches. The simulation approach is validated by means of comparisons to both computational and experimental results for a number of relevant systems including particle-liquid separation in an inclined channel, particle sedimentation in a liquid, and gas-particle fluidised beds. This new method is shown to compare very favourably in terms of both the accuracy of the results and the computational cost required to achieve them.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"182 ","pages":"Article 105033"},"PeriodicalIF":3.6,"publicationDate":"2024-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142578646","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}
Pub Date : 2024-10-18DOI: 10.1016/j.ijmultiphaseflow.2024.105026
Tanjina Azad, Yue Ling
The interfacial instability in a two-phase mixing layers between parallel gas and liquid streams is important to two-phase atomization. Depending on the inflow conditions and fluid properties, interfacial instability can be convective or absolute. The goal of the present study is to investigate the impact of gas viscosity on the interfacial instability. Both interface-resolved simulations and linear stability analysis (LSA) have been conducted. In LSA, the Orr–Sommerfeld equation is solved to analyze the spatio-temporal viscous modes. When the gas viscosity decreases, the Reynold number () increases accordingly. The LSA demonstrates that when is higher than a critical threshold, the instability transitions from the absolute to the convective (A/C) regimes. Such a -induced A/C transition is also observed in the numerical simulations, though the critical Re observed in simulations is significantly lower than that predicted by LSA. The LSA results indicate that the temporal growth rate decreases with Re. When the growth rate reaches zero, the A/C transition will occur. The -induced A/C transition is observed in both confined and unconfined mixing layers and also in cases with low and high gas-to-liquid density ratios. In the transition from typical absolute and convective regimes, a weak absolute regime is identified in the simulations, for which the spectrograms show both the absolute and convective modes. The dominant frequency in the weak absolute regime can be influenced by the perturbation introduced at the inlet. The simulation results also show that the wave propagation speed can vary in space. In the absolute instability regime, the wave propagation speed agrees well with the absolute mode celerity near the inlet and increases to the Dimotakis speed further downstream.
平行气流和液流两相混合层中的界面不稳定性对两相雾化非常重要。根据流入条件和流体特性的不同，界面不稳定性可以是对流的，也可以是绝对的。本研究的目的是探讨气体粘度对界面不稳定性的影响。我们进行了界面分辨模拟和线性稳定性分析（LSA）。在线性稳定性分析中，通过求解 Orr-Sommerfeld 方程来分析时空粘性模式。当气体粘度降低时，雷诺数（Re）会相应增加。LSA 证明，当 Re 高于临界阈值时，不稳定性会从绝对状态过渡到对流状态（A/C）。在数值模拟中也观察到了这种由 Re 引发的 A/C 过渡，尽管模拟中观察到的临界 Re 远远低于 LSA 预测的临界 Re。LSA 结果表明，时间增长率随 Re 值减小。当增长率为零时，将发生空调过渡。在密闭和非密闭混合层中，以及在低气液密度比和高气液密度比的情况下，都可以观察到再诱导的 A/C 过渡。在从典型的绝对和对流状态过渡的过程中，模拟确定了一个弱绝对状态，其频谱图显示了绝对和对流模式。弱绝对状态下的主导频率会受到入口处引入的扰动的影响。模拟结果还表明，波的传播速度可以在空间中变化。在绝对不稳定系统中，波的传播速度与入口附近的绝对模式速度非常一致，并在下游增加到迪莫塔基斯速度。
{"title":"Effect of gas viscosity on the interfacial instability development in a two-phase mixing layer","authors":"Tanjina Azad, Yue Ling","doi":"10.1016/j.ijmultiphaseflow.2024.105026","DOIUrl":"10.1016/j.ijmultiphaseflow.2024.105026","url":null,"abstract":"<div><div>The interfacial instability in a two-phase mixing layers between parallel gas and liquid streams is important to two-phase atomization. Depending on the inflow conditions and fluid properties, interfacial instability can be convective or absolute. The goal of the present study is to investigate the impact of gas viscosity on the interfacial instability. Both interface-resolved simulations and linear stability analysis (LSA) have been conducted. In LSA, the Orr–Sommerfeld equation is solved to analyze the spatio-temporal viscous modes. When the gas viscosity decreases, the Reynold number (<span><math><mtext>Re</mtext></math></span>) increases accordingly. The LSA demonstrates that when <span><math><mtext>Re</mtext></math></span> is higher than a critical threshold, the instability transitions from the absolute to the convective (A/C) regimes. Such a <span><math><mtext>Re</mtext></math></span>-induced A/C transition is also observed in the numerical simulations, though the critical Re observed in simulations is significantly lower than that predicted by LSA. The LSA results indicate that the temporal growth rate decreases with Re. When the growth rate reaches zero, the A/C transition will occur. The <span><math><mtext>Re</mtext></math></span>-induced A/C transition is observed in both confined and unconfined mixing layers and also in cases with low and high gas-to-liquid density ratios. In the transition from typical absolute and convective regimes, a weak absolute regime is identified in the simulations, for which the spectrograms show both the absolute and convective modes. The dominant frequency in the weak absolute regime can be influenced by the perturbation introduced at the inlet. The simulation results also show that the wave propagation speed can vary in space. In the absolute instability regime, the wave propagation speed agrees well with the absolute mode celerity near the inlet and increases to the Dimotakis speed further downstream.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"181 ","pages":"Article 105026"},"PeriodicalIF":3.6,"publicationDate":"2024-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142526836","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}
Forced imbibition dynamics are critical for enhancing recovery rates in reservoirs, as efficient fluid displacement directly impacts resource extraction. This study employs the Zou-He velocity boundary condition and a modified convective boundary condition (mCBC) within the multi-component Shan-Chen lattice Boltzmann method (LBM), thus facilitating unobstructed flow of multi-component fluids at the outlet while maintaining constant outlet pressure. The model's validity was established through outflow tests of immiscible droplets in channels. Its accuracy was further confirmed by comparing results from forced imbibition dynamics tests in dual-wetted pores with theoretical predictions. A symmetrical porous medium was constructed using the stacking method, achieving dual wettability by fixing the contact angle in the upper region and varying it in the lower region. We performed 20 simulation sets under unfavorable viscosity ratios and varying capillary numbers, focusing on overall displacement efficiency before and after breakthrough, and employing energy balance equations to evaluate the dominant forces. Results reveal that capillary forces predominantly dictate forced imbibition dynamics in low capillary number scenarios. In strongly wetted regions, the invading fluid fully occupies pore spaces; however, in weakly wetted regions, displacement efficiency significantly declines as wettability approaches neutrality, even nearing zero. As capillary numbers increase, viscous forces become more prominent, controlling dynamics and leading to fingering and trapping of defending fluids. In weakly wetted areas, the increasing influence of viscous forces enhances fluid displacement, resulting in significant improvements in overall displacement efficiency compared to conditions dominated by capillary forces.
{"title":"Lattice Boltzmann modeling of forced imbibition dynamics in dual-wetted porous media","authors":"Shengting Zhang , Jing Li , Rodrigo C.V. Coelho , Keliu Wu , Qingyuan Zhu , Shiqiang Guo , Zhangxin Chen","doi":"10.1016/j.ijmultiphaseflow.2024.105035","DOIUrl":"10.1016/j.ijmultiphaseflow.2024.105035","url":null,"abstract":"<div><div>Forced imbibition dynamics are critical for enhancing recovery rates in reservoirs, as efficient fluid displacement directly impacts resource extraction. This study employs the Zou-He velocity boundary condition and a modified convective boundary condition (mCBC) within the multi-component Shan-Chen lattice Boltzmann method (LBM), thus facilitating unobstructed flow of multi-component fluids at the outlet while maintaining constant outlet pressure. The model's validity was established through outflow tests of immiscible droplets in channels. Its accuracy was further confirmed by comparing results from forced imbibition dynamics tests in dual-wetted pores with theoretical predictions. A symmetrical porous medium was constructed using the stacking method, achieving dual wettability by fixing the contact angle in the upper region and varying it in the lower region. We performed 20 simulation sets under unfavorable viscosity ratios and varying capillary numbers, focusing on overall displacement efficiency before and after breakthrough, and employing energy balance equations to evaluate the dominant forces. Results reveal that capillary forces predominantly dictate forced imbibition dynamics in low capillary number scenarios. In strongly wetted regions, the invading fluid fully occupies pore spaces; however, in weakly wetted regions, displacement efficiency significantly declines as wettability approaches neutrality, even nearing zero. As capillary numbers increase, viscous forces become more prominent, controlling dynamics and leading to fingering and trapping of defending fluids. In weakly wetted areas, the increasing influence of viscous forces enhances fluid displacement, resulting in significant improvements in overall displacement efficiency compared to conditions dominated by capillary forces.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"182 ","pages":"Article 105035"},"PeriodicalIF":3.6,"publicationDate":"2024-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142554489","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-15DOI: 10.1016/j.ijmultiphaseflow.2024.105021
Vlad Giurgiu , Leonel Beckedorff , Giuseppe C.A. Caridi , Christian Lagemann , Alfredo Soldati
A machine learning-based approach, RAFT-PIV, is used to measure with single-pixel resolution the flow field around a microplastic fiber in a turbulent channel flow at a Shear Reynolds number of 1000. The results reveal the interaction of the fiber with a hairpin vortex. The fiber rotation rate is correlated with slip velocity distributions along the fiber length, demonstrating higher rotation rates with increased slip velocity gradients. The fiber’s alignment with the spanwise direction during its trajectory is explained through its progressive alignment with the head of a hairpin vortex, characterized by the swirling strength, shear strain rate, and local flow velocity. Higher fiber rotation rates were found likelier in the presence of a vortical structure. These findings highlight the potential of machine learning-enhanced PIV techniques to deepen our understanding of fiber-turbulence interactions, essential for applications such as microplastic pollution mitigation.
{"title":"Machine learning-enhanced PIV for analyzing microfiber-wall turbulence interactions","authors":"Vlad Giurgiu , Leonel Beckedorff , Giuseppe C.A. Caridi , Christian Lagemann , Alfredo Soldati","doi":"10.1016/j.ijmultiphaseflow.2024.105021","DOIUrl":"10.1016/j.ijmultiphaseflow.2024.105021","url":null,"abstract":"<div><div>A machine learning-based approach, RAFT-PIV, is used to measure with single-pixel resolution the flow field around a microplastic fiber in a turbulent channel flow at a Shear Reynolds number of 1000. The results reveal the interaction of the fiber with a hairpin vortex. The fiber rotation rate is correlated with slip velocity distributions along the fiber length, demonstrating higher rotation rates with increased slip velocity gradients. The fiber’s alignment with the spanwise direction during its trajectory is explained through its progressive alignment with the head of a hairpin vortex, characterized by the swirling strength, shear strain rate, and local flow velocity. Higher fiber rotation rates were found likelier in the presence of a vortical structure. These findings highlight the potential of machine learning-enhanced PIV techniques to deepen our understanding of fiber-turbulence interactions, essential for applications such as microplastic pollution mitigation.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"181 ","pages":"Article 105021"},"PeriodicalIF":3.6,"publicationDate":"2024-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142526772","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}
Pub Date : 2024-10-12DOI: 10.1016/j.ijmultiphaseflow.2024.105025
Simone Borneto, Carlo Cravero, Alessandro Lamberti, Davide Marsano
The usage of air bubblers plays an important role in the glass-making industrial process because it enhances the global heat transfer efficiency and especially the uniformity and quality of the finished products. However, glass manufacturers rely on field practice to run their plants, due to the extreme difficulty of conducting experimental investigations in melting tanks. CFD analysis represents a powerful tool to optimize operating parameters and positioning of bubblers and other components, not only in existing plants, but also in the design of new furnaces.
In the present paper, the behaviour of bubble columns in highly viscous liquids at high temperature was analysed using the Eulerian multiphase model. The macroscopic effect of the column on the surrounding fluid was translated in a locally momentum source term that was introduced in the single-phase CFD model developed in this study. This solution approximates the multiphase nature of the problem in a reliable way and it is of fast integration in comprehensive models of furnaces.
A clear methodology to determine the diameter of the bubbles and the velocity of the bubble chain in the buoyancy source term calculus are presented and analysed in detail. In addition, a validation process based on the comparison with other theoretical and empirical studies on the subject was carried out in detail: it includes the evaluation of the bubble chains properties and effects by varying the liquid viscosity and the inlet gas flow, that is the real operational parameter in industry. Moreover, the effects of the variable height of the bubblers were investigated using the results of a single-phase model of a real industrial glass tank.
The analysis of the obtained results shows that the model and the calculation methodologies followed in this work can be effectively applied in the dimensioning process of industrial glass tanks or to optimize existing plants.
{"title":"Simulation and modelling approach for bubblers effect into molten glass tank","authors":"Simone Borneto, Carlo Cravero, Alessandro Lamberti, Davide Marsano","doi":"10.1016/j.ijmultiphaseflow.2024.105025","DOIUrl":"10.1016/j.ijmultiphaseflow.2024.105025","url":null,"abstract":"<div><div>The usage of air bubblers plays an important role in the glass-making industrial process because it enhances the global heat transfer efficiency and especially the uniformity and quality of the finished products. However, glass manufacturers rely on field practice to run their plants, due to the extreme difficulty of conducting experimental investigations in melting tanks. CFD analysis represents a powerful tool to optimize operating parameters and positioning of bubblers and other components, not only in existing plants, but also in the design of new furnaces.</div><div>In the present paper, the behaviour of bubble columns in highly viscous liquids at high temperature was analysed using the Eulerian multiphase model. The macroscopic effect of the column on the surrounding fluid was translated in a locally momentum source term that was introduced in the single-phase CFD model developed in this study. This solution approximates the multiphase nature of the problem in a reliable way and it is of fast integration in comprehensive models of furnaces.</div><div>A clear methodology to determine the diameter of the bubbles and the velocity of the bubble chain in the buoyancy source term calculus are presented and analysed in detail. In addition, a validation process based on the comparison with other theoretical and empirical studies on the subject was carried out in detail: it includes the evaluation of the bubble chains properties and effects by varying the liquid viscosity and the inlet gas flow, that is the real operational parameter in industry. Moreover, the effects of the variable height of the bubblers were investigated using the results of a single-phase model of a real industrial glass tank.</div><div>The analysis of the obtained results shows that the model and the calculation methodologies followed in this work can be effectively applied in the dimensioning process of industrial glass tanks or to optimize existing plants.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"181 ","pages":"Article 105025"},"PeriodicalIF":3.6,"publicationDate":"2024-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142526834","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}
Twin-fluid atomizers, valued for handling viscous fluids and high operating loads, are extensively used in combustion processes and oil refineries. In the latter scenario, internal mixing nozzles are employed in fluid catalytic cracking units for oil dispersion using steam as the dispersing medium. While steam-assisted atomization studies often focus on flue gas analysis, the associated steam/oil internal mixing process and the spray droplet dynamics lack proper investigation. Accordingly, this work explores the Y-jet nozzle performance for oil atomization using steam, aiming to determine favorable conditions for obtaining a stable spray with fine droplet distribution. This analysis is accomplished by characterizing the mixing chamber pressure, investigating the spray boundary instabilities using high-speed images, and exploring the spray droplet size using the shadowgraphy technique. Work relevance relies on performing experiments at industrially representative conditions, characterized by the similarity of important dimensionless numbers. Additionally, the nozzle design is optimized by varying key geometric parameters. The nozzle geometry and the operating condition impacts on the steam-assisted atomization performance and spray behavior constitute the main findings of this work. The outcomes highlight the relevance of the fluid dynamics investigation for optimized nozzle performance, involving a balance between spray stability and fine droplet distribution generation.
双流体雾化器具有处理粘性流体和高工作负荷的特点，被广泛应用于燃烧过程和炼油厂。在后一种情况下，流体催化裂化装置中使用内部混合喷嘴，以蒸汽为分散介质进行油分散。蒸汽辅助雾化研究通常侧重于烟气分析，而对相关的蒸汽/油内部混合过程和喷雾液滴动力学缺乏适当的研究。因此，本研究探讨了使用蒸汽雾化油类的 Y 型喷嘴性能，旨在确定获得稳定喷雾和精细雾滴分布的有利条件。这项分析是通过确定混合室压力、使用高速图像研究喷雾边界不稳定性以及使用阴影成像技术探索喷雾液滴大小来完成的。工作的相关性依赖于在具有工业代表性的条件下进行实验，这些条件的特点是重要的无量纲数字相似。此外，还通过改变关键几何参数来优化喷嘴设计。喷嘴几何形状和工作条件对蒸汽辅助雾化性能和喷雾行为的影响构成了这项工作的主要发现。研究结果凸显了流体动力学研究对优化喷嘴性能的意义，其中涉及喷雾稳定性和细微液滴分布生成之间的平衡。
{"title":"Spray characteristics of steam-assisted oil atomization in Y-jet nozzles","authors":"Matheus Rover Barbieri , Lydia Achelis , Udo Fritsching","doi":"10.1016/j.ijmultiphaseflow.2024.105028","DOIUrl":"10.1016/j.ijmultiphaseflow.2024.105028","url":null,"abstract":"<div><div>Twin-fluid atomizers, valued for handling viscous fluids and high operating loads, are extensively used in combustion processes and oil refineries. In the latter scenario, internal mixing nozzles are employed in fluid catalytic cracking units for oil dispersion using steam as the dispersing medium. While steam-assisted atomization studies often focus on flue gas analysis, the associated steam/oil internal mixing process and the spray droplet dynamics lack proper investigation. Accordingly, this work explores the Y-jet nozzle performance for oil atomization using steam, aiming to determine favorable conditions for obtaining a stable spray with fine droplet distribution. This analysis is accomplished by characterizing the mixing chamber pressure, investigating the spray boundary instabilities using high-speed images, and exploring the spray droplet size using the shadowgraphy technique. Work relevance relies on performing experiments at industrially representative conditions, characterized by the similarity of important dimensionless numbers. Additionally, the nozzle design is optimized by varying key geometric parameters. The nozzle geometry and the operating condition impacts on the steam-assisted atomization performance and spray behavior constitute the main findings of this work. The outcomes highlight the relevance of the fluid dynamics investigation for optimized nozzle performance, involving a balance between spray stability and fine droplet distribution generation.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"181 ","pages":"Article 105028"},"PeriodicalIF":3.6,"publicationDate":"2024-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142526838","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}
Pub Date : 2024-10-11DOI: 10.1016/j.ijmultiphaseflow.2024.105014
Ehsan Amani, Saeid Abdi-Sij
The accurate prediction of the drop–wall impact dynamics and regime are of interest in many engineering applications. Considerable progress has been made in different elements of Direct Numerical Simulation (DNS) approaches. However, identifying the optimal combination of improved submodels that perform well under a wide range of operating conditions, covering low to high Weber numbers with varying surface wettabilities and wall motions, still requires further investigation. Here, we conduct a comparative study on the performance of key DNS elements, including the Interface Tracking (IT) algorithm for the widely-used volume-of-fluid approach, Contact Angle (CA), Contact-Line Velocity (CLV), Instability Actuation (IA), and numerical discretization. The study spans a broad range of Weber numbers, encompassing various impact phenomena such as drop oscillation, partial rebound, fingering, and splash. It is concluded that the Kistler CA model provides the most accurate predictions among the models considered here. In terms of IT, the Multidimensional Universal Limiter with Explicit Solution (MULES) algorithm is the most efficient one, especially for moderate to high Weber numbers. For high Weber numbers, involving the fingering instability and splash events, while applying the IA mechanism slightly improves the results, using a high-quality fine-enough grid and appropriate numerical discretization scheme to control the dispersion and dissipation errors are more important ingredients. It is shown that the recommended model combination is also able to predict the important features of drop impact on moving walls with reasonable accuracy.
在许多工程应用中，对落壁式冲击动力学和机制的精确预测都很重要。直接数值模拟（DNS）方法的不同要素已经取得了长足的进步。然而，如何确定改进子模型的最佳组合，使其在从低到高韦伯数、不同表面润湿性和壁面运动的各种操作条件下都能表现良好，仍需要进一步研究。在此，我们对关键 DNS 元素的性能进行了比较研究，包括广泛使用的流体容积方法的界面跟踪 (IT) 算法、接触角 (CA)、接触线速度 (CLV)、不稳定性作用 (IA) 和数值离散化。研究跨越了韦伯数字的广泛范围，涵盖了各种冲击现象，如水滴振荡、部分反弹、指压和飞溅。结论是，在本文所考虑的模型中，Kistler CA 模型的预测结果最为准确。在信息技术方面，具有显式求解的多维通用限幅器（MULES）算法是最有效的算法，特别是对于中高韦伯数。对于涉及指状不稳定性和飞溅事件的高韦伯数，虽然采用 IA 机制能略微改善结果，但使用足够精细的高质量网格和适当的数值离散化方案来控制分散和耗散误差更为重要。结果表明，推荐的模型组合也能以合理的精度预测水滴撞击运动壁面的重要特征。
{"title":"Direct numerical simulation of droplet impact onto dry stationary and moving walls at low to high Weber numbers","authors":"Ehsan Amani, Saeid Abdi-Sij","doi":"10.1016/j.ijmultiphaseflow.2024.105014","DOIUrl":"10.1016/j.ijmultiphaseflow.2024.105014","url":null,"abstract":"<div><div>The accurate prediction of the drop–wall impact dynamics and regime are of interest in many engineering applications. Considerable progress has been made in different elements of Direct Numerical Simulation (DNS) approaches. However, identifying the optimal combination of improved submodels that perform well under a wide range of operating conditions, covering low to high Weber numbers with varying surface wettabilities and wall motions, still requires further investigation. Here, we conduct a comparative study on the performance of key DNS elements, including the Interface Tracking (IT) algorithm for the widely-used volume-of-fluid approach, Contact Angle (CA), Contact-Line Velocity (CLV), Instability Actuation (IA), and numerical discretization. The study spans a broad range of Weber numbers, encompassing various impact phenomena such as drop oscillation, partial rebound, fingering, and splash. It is concluded that the Kistler CA model provides the most accurate predictions among the models considered here. In terms of IT, the Multidimensional Universal Limiter with Explicit Solution (MULES) algorithm is the most efficient one, especially for moderate to high Weber numbers. For high Weber numbers, involving the fingering instability and splash events, while applying the IA mechanism slightly improves the results, using a high-quality fine-enough grid and appropriate numerical discretization scheme to control the dispersion and dissipation errors are more important ingredients. It is shown that the recommended model combination is also able to predict the important features of drop impact on moving walls with reasonable accuracy.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"181 ","pages":"Article 105014"},"PeriodicalIF":3.6,"publicationDate":"2024-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142441134","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-11DOI: 10.1016/j.ijmultiphaseflow.2024.105024
Dag Chun Standnes, Einar Ebeltoft, Åsmund Haugen, Anders Kristoffersen
This work presents a governing equation (GE) for two-phase flow in porous media connecting capillary pressure to frictional pressure loss and external chemical potential supplied to a system in either stationary or diffusive equilibrium. It is based on the difference between non-wetting and wetting phase chemical potential (physically, pressure or energy density), which leads to a generalization of the capillary pressure concept. The difference in phase internal chemical potentials is characterized by changes in both interfacial areas and entropy densities due to variation in fluid saturations and is balanced by the system external chemical potential supplied. A definition of the capillary pressure concept is formulated based on the diffusive equilibrium criterion. The GE can explain the origin of the dynamic capillary pressure term, hysteresis, and connect the shift in the capillary pressure curve upon injecting water phases with varying salinities to all the other chemical potentials acting. It can connect, constrain, and potentially quantify all effects which can be formulated in terms of chemical potentials since it is based on a balance equation all two-phase flow systems must obey when either in stationary or diffusive equilibrium.
{"title":"Using the total chemical potential to generalize the capillary pressure concept and therefrom derive a governing equation for two-phase flow in porous media","authors":"Dag Chun Standnes, Einar Ebeltoft, Åsmund Haugen, Anders Kristoffersen","doi":"10.1016/j.ijmultiphaseflow.2024.105024","DOIUrl":"10.1016/j.ijmultiphaseflow.2024.105024","url":null,"abstract":"<div><div>This work presents a governing equation (GE) for two-phase flow in porous media connecting capillary pressure to frictional pressure loss and external chemical potential supplied to a system in either stationary or diffusive equilibrium. It is based on the difference between non-wetting and wetting phase chemical potential (physically, pressure or energy density), which leads to a generalization of the capillary pressure concept. The difference in phase internal chemical potentials is characterized by changes in both interfacial areas and entropy densities due to variation in fluid saturations and is balanced by the system external chemical potential supplied. A definition of the capillary pressure concept is formulated based on the diffusive equilibrium criterion. The GE can explain the origin of the dynamic capillary pressure term, hysteresis, and connect the shift in the capillary pressure curve upon injecting water phases with varying salinities to all the other chemical potentials acting. It can connect, constrain, and potentially quantify all effects which can be formulated in terms of chemical potentials since it is based on a balance equation all two-phase flow systems must obey when either in stationary or diffusive equilibrium.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"181 ","pages":"Article 105024"},"PeriodicalIF":3.6,"publicationDate":"2024-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142526835","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}
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