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Motion of a rigid particle in the lid-driven cavity flow

Chinese Physics B 2025年第3期34卷 448-459页

作者： Fan Yang Zhe Yan Wencan Wang Ren Shi School of Energy and Power Engineering University of Shanghai for Science and TechnologyShanghai 200093China Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering Shanghai 200093China

The motion of an elliptical rigid particle in a lid-driven cavity flow was numerically simulated using the immersed boundary lattice Boltzmann method(IB-LBM).The effects of the particle's initial orientation angle,initial position,aspect ratio,and size on the motion characteristics were *** computational results indicate that the particle's motion undergoes two distinct stages:a starting stage that involves moving from the release position to a limit cycle,and a periodic stage that involves moving on the limit *** initial orientation of the particle has a minimal impact on both stages of *** contrast,the time it takes for the particle to reach the limit cycle may vary depending on the release ***,particles with a larger aspect ratio exhibit a greater maximum velocity magnitude;an increase in particle size causes the particle trajectory to contract more toward the center of the cavity,decreasing the centrifugal force experienced by the particle.

关键词： lattice Boltzmann methods immersed boundary method elliptical rigid particle lid-driven cavity flow

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Three-dimensional numerical study on flow control of two-phase flow around a cylinder with an auxiliary miniature cylinder

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PHYSICS OF FLUIDS 2025年第4期37卷

作者： Xie, Yunqi Hu, Yu Huang, Shengxian Wang, Ying Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai Peoples R China

In ocean engineering, studying the phenomena of flow separation, vortex shedding, and particle deposition around blunt bodies is crucial, as these factors significantly affect the performance, stability, and lifespan of marine structures. This study, conducted under realistic marine conditions with a Reynolds number of Re = 2.5 x 10(5), and accounting for gravitational effects, first investigates the impact of installing auxiliary miniature cylinders at the front edge of the primary cylinder with different gap ratios, aiming to identify the optimal gap ratio. Subsequently, trailing-edge miniature cylinders are added for comparative analysis. This study also explores the effects of vibrating upstream miniature cylinders. Additionally, it examines the influence of auxiliary miniature cylinders on particle distribution in the wake region under particle-laden flow. The results indicate that miniature cylinders at specific gap ratios significantly reduce the drag and lift coefficients of the primary cylinder, suppress vortex shedding, optimize wake structures, and weaken the horseshoe vortex. While vibrating cylinders reduce vortex suppression, high-frequency vibrations contribute to greater drag reduction. Upstream miniature cylinders reduce the influence of vortex structures in the wake but increase sediment deposition. A dual-cylinder configuration is the most effective method for controlling sediment concentration distribution at the base of the primary cylinder.

关键词： Vortex flow

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Comparison of three-component co-pyrolytic char and corn straw biochar for assisting water electrolysis to achieve efficient hydrogen production

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JOURNAL OF power SOURCES 2025年 630卷

作者： Chen, Xinyue Ying, Zhi Sun, Hao Zheng, Xiaoyuan Dou, Binlin Cui, Guomin Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai 200093 Peoples R China

Biochar-assisted water electrolysis (BAWE) technology can effectively reduce the energy consumption for hydrogen production and achieve the upcycling of biochar. However, the identification of highly active and efficient biochar remains a pressing need for BAWE process. Herein, we initially employ the three primary components of cellulose, hemicellulose and lignin in corn straw and the raw corn straw to produce char and biochar, respectively, followed by a systematic comparison of the biochar oxidation reaction (BOR) of char and biochar in BAWE process. The char exhibits superior BOR kinetics compared to biochar, mostly attributed to its exposed surface and porous structure. But HCl pickling of biochar moderately removes ash and enhances hydrophilicity, thereby improving BOR kinetics. For both char and biochar-assisted water electrolysis at 150 mA cm-2, nearly 100 % of Faradaic efficiency for hydrogen production is reached;both char and biochar are enriched with oxygen-containing functional groups such as -OH, C-O, and C=O, alongside enhanced hydrophilicity. Furthermore, the presence of CO2, 2 , CO, and O22 in anodic mixed gas confirms the competition between BOR and oxygen evolution reaction. This work establishes a foundation for efficient hydrogen pro- duction and electrochemical modification of biochar in BAWE process.

关键词： Biochar-assisted water electrolysis (BAWE) Hydrogen Biochar oxidation reaction (BOR) Kinetics

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Meniscus-guided 3D printing with material supplied by the intrinsic capillary replenishment flow: Printing success rate, printed structure size adjustment, and microscale functional device fabrication

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JOURNAL OF MATERIALS PROCESSING TECHNOLOGY 2025年 339卷

作者： Cai, Rongze Wang, Haiyang Han, Xueqing Wang, Dongmin Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai 200093 Peoples R China

Meniscus-guided 3D printing is a microscale ink-based 3D printing technique, which features ease of operation and can print micro/nano functional devices of multiple types of materials at a low cost. However, the customized microscale functional device fabrication challenge remains, because the critical printing conditions for successful printing are complex. Whether the printed device efficiency depends on printing conditions is unclear. Our study shows that there exist clogging and terminated critical pulling speeds in meniscus-guided 3D printing with material supplied by the evaporation-induced capillary replenishment flow, where only the pulling speed is within this range 3D printing could be successfully implemented. The printable ink viscosity can be higher than the previously reported if the pulling speed criterion is satisfied. The critical pulling speeds and the interval between them decrease with the micropipette diameter or ambient humidity. A more comprehensive formulation than the literature reported ones describing the dependence of the 3D-printed micropillar diameter on the micropipette pulling velocity and diameter is derived, which agrees well with the experimentally printed micropillar diameters under different conditions and indicates that 3D-printed micropillar diameter adjustment is governed by the meniscus shape and its evaporation rate. Based on the improved 3D-printed structure adjustment technology, the 3D microbridge humidity sensors and 3D micropillar capacitor electrodes can be fabricated with high repeatability and efficiency. The 3D-printed microscale devices' efficiencies in this study are superior to most previously reported microscale devices, with their efficiencies adjustable by the relative humidity during the printing process. Furthermore, the 3D-printed humidity sensor is demonstrated to be used as a contactless finger sensor, which shows potential application in preventing disease cross-infection in public facilities. Improveme

关键词： Meniscus-guided 3D printing Capillary replenishment flow Evaporation Nanoparticle deposition Micro humidity sensor Micro capacitor

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Effects of pretreatment on biochar oxidation reaction and hydrogen production in lignocellulosic biochar-assisted water electrolysis

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INTERNATIONAL JOURNAL OF HYDROGEN ENERGY 2025年 99卷 752-760页

作者： Sun, Hao Ying, Zhi Chen, Xinyue Zheng, Xiaoyuan Dou, Binlin Cui, Guomin Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai 200093 Peoples R China

Substituting the oxygen evolution reaction in water electrolysis with the thermodynamically more favorable biochar oxidation reaction (BOR) constitutes biochar-assisted water electrolysis (BAWE), presenting a promising strategy for energy-efficient hydrogen production and high-value utilization biochar. Nevertheless, the BOR suffers from the sluggish kinetics and ambiguous selectivity with respect to ungraded biochar. Herein, we demonstrate the effects of elution treatment on pyrolytic lignocellulosic biochar concerning BOR kinetics and hydrogen production, as well as the efficiency of electrooxidized biochar in Cr(VI) removal. The original lignocellulosic biochar washed by alkali, acid, and water exhibited an improved BOR kinetics. Notably, the moderate water washing favored the removal of ash and soluble substances, thereby exposing more easily oxidizable functional groups such as C-OH and COOH, which substantially enhanced BOR kinetics. The waterwashed biochar-assisted water electrolysis achieved a Faradaic efficiency of 99.5% for hydrogen production at 50 mA cm-2, necessitating lower cell voltages compared to unwashed biochar. Water elution pretreatment also promoted the sufficient oxidation of biochar during electrolysis, with enriched oxygen-containing functional groups like C-O contributing to an increase in Cr(VI) removal rate from 20.81% to 65.10%. This work offers strategies for achieving efficient biochar upgrading and hydrogen production in the BAWE process.

关键词： Biochar-assisted water electrolysis Elution treatment Electrooxidation Hydrogen production Cr(VI) adsorption

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Theoretical study of bubble departure and lift-off diameters model for evaporation based on microlayer in flow boiling

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INTERNATIONAL JOURNAL OF THERMAL SCIENCES 2025年 214卷

作者： Dong, Wu-han Gao, Ming Shen, Zhong-xiang Dang, Meng-yuan Zhang, Li-xin Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai 200093 Peoples R China

This study was devoted to the theory of microlayer evaporation and bubble dynamics. In subcooled flowing boiling, a theoretical study of the mechanism of heat and mass transfer in vapor bubbles during boiling heat transfer has been carried out. The forces on mononuclear boiling bubbles during subcooled flow boiling are analyzed. In addition, the effect of microlayer evaporation was considered, and microlayer evaporation force has been introduced. Evaporation of the microlayers as between the bottom of a bubble and the heated wall, evaporation of the layer of superheated liquid around the bubble, the condensation of the vapors at the top of a bubble are taken into account on the basis of the bubble dynamics. The prediction models for bubble forces, departure and lift-off diameters were improved. The influence of force on the bubble under the same working conditions was also investigated. Compared with previous experimental results, it was found that the improved model could forecast the diameters of the bubble departure and bubble lift-off well.

关键词： Bubble Microlayer flow boiling Wall temperature Theoretical model Nomenclature

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Dynamics of post-impact merged droplets under different droplet-droplet interaction modes upon successive impingement on the substrate of different wettabilities

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PHYSICS OF FLUIDS 2025年第1期37卷

作者： Zhou, Junjie Wang, Dongmin Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai 200093 Peoples R China

Successive impingement of multiple droplets onto a substrate is common in applications. However, the effects of the substrate properties and droplet-droplet interaction modes on the dynamics of the post-impact merged droplet remain unclear. In this study, we simulate the successive impingement of two droplets and the dynamics of the merged droplet on a superhydrophobic surface and a hydrophilic-hydrophobic patterned surface under different droplet-droplet interaction modes, based on a two-dimensional single-component pseudopotential multiphase lattice Boltzmann model. On the superhydrophobic surface, if the leading droplet is at spreading stages upon successive impingement, the merged droplet's maximum spreading factor, rebounding height, and merged droplet-substrate contact time decrease with the spreading of the leading droplet. Conversely, if the leading droplet is at recoiling stages upon successive impingement, the merged droplet's maximum spreading factor and rebounding height remain a small constant, while the merged droplet-substrate contact time increases with recoiling of the leading droplet. The dynamics of the merged droplet on a superhydrophobic surface under different droplet-droplet interaction modes are attributed to amplifying or suppressing the leading droplet kinetic energy upon successive impingement. However, on the hydrophilic-hydrophobic patterned surface, it is found that the hydrophilic stripes enhance the merged droplet spreading. The relatively large viscous force of the hydrophilic stripes and the energy barrier at the boundary of the pattern stripes significantly dissipate the kinetic energy of the merged droplet. The merged droplet does not rebound on the hydrophilic-hydrophobic patterned surface and has a small oscillation amplitude and fast energy decay rate.

关键词： Kinetic energy

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Performance comparison investigation on different pulse tube position heat pumps with power recovery displacer

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International Journal of Refrigeration 2025年 176卷 1-16页

作者： Zhu, Shenglin Chen, Xi Zhu, Yifan Qi, Yingxia School of Energy and Power Engineering University of Shanghai for Science and Technology 516 Jungong Road Shanghai200093 China Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering University of Shanghai for Science and Technology 516 Jungong Road Shanghai200093 China

Spacecraft waste heat is dissipated into space primarily by radiation. To improve the heat dissipation efficiency of spacecraft radiators in high-temperature environments and reduce heat wastage in spaceflight thermal control systems, thermoacoustic heat pumps (TAHP) are considered a viable method for increasing radiator cooling temperatures and recovering waste heat. In this study, one-dimensional simulations are used to optimize the geometrical parameters of the 100-watt work recovery thermoacoustic heat pump (WRTAHP) for various pulse tube positions. The performances of the two systems are compared at a cold-end temperature of 293 K and a hot-end temperature of 353 K. The results reveal that a heating capacity of 256 W with a relative Carnot efficiency of 35.01 % is achieved for the pulse tube front-type thermoacoustic heat pump (FTTAHP), whereas the pulse tube back-type thermoacoustic heat pump (BTTAHP) obtains a heating capacity of 225 W with a relative Carnot efficiency of 30.59 %. As the cold-end temperature decreases, the coefficient of performance is reduced for FTTAHP, while the performance of BTTAHP shows a substantial improvement. At a cold end temperature of 233 K and a hot-cold end temperature difference of 60 K, a heating capacity of 268 W with a relative Carnot efficiency of 50.57 % is achieved for BTTAHP. Furthermore, the heating capacity of the BTTAHP is not significantly increased by adopting the active phase adjustment structure. In summary, the FTTAHP is suitable for spacecraft radiator applications and avoids high temperatures affecting compressor operation, whereas the BTTAHP is better suited for low-temperature heating. © 2025 Elsevier Ltd and IIR

关键词： Waste heat utilization

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Study on Particle Sedimentation in a Cavity Containing Obstacles

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PROCESSES 2025年第4期13卷 980-980页

作者： Yang, Fan Shi, Ren Yan, Zhe Wang, Wencan Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai 200093 Peoples R China Shanghai Key Lab Multiphase Flow & Heat Transfer Shanghai 200093 Peoples R China

The sedimentation of particles has a wide range of application scenarios in industry. In this paper, the sedimentation of a single particle in a cavity containing obstacles is simulated using the immersed boundary-lattice Boltzmann method. The computational results show that the presence of obstacles will alter the sedimentation of the particle, and the particle will undergo a change in the direction of rotation during the period when it tumbles over the surface of the obstacle and continues to sedimentation after leaving the obstacle. Increasing the particle-obstacle eccentricity or decreasing the particle-obstacle diameter ratio will shorten the particle-obstacle interaction time. When the sedimentation of a particle passes through the gap between two obstacles, it can be influenced by the far-side obstacle and interact with the near-side obstacle for a second time, and the influence of the far-side obstacle on the sedimentation of the particle disappears when the gap between the two obstacles exceeds a certain threshold. These results quantitatively elucidate the critical role of obstacle configuration in modulating particle dynamics, providing valuable insights for optimizing industrial sedimentation systems and advancing predictive models for multiphase flows in complex geometries.

关键词： particle sedimentation lattice Boltzmann method immersed boundary method

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Numerical study on the effect of rim seal slot filleting on turbine endwall cooling

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AIP ADVANCES 2025年第1期15卷

作者： Li, Xinchun Wei, Na Shi, Liuliu Chen, Eryun Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai 200093 Peoples R China Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai 200093 Peoples R China

In this study, the effect of rim seal slot filleting on turbine endwall film cooling performance is numerically investigated. For comparison with the baseline case, five different fillet radius and width (R/W) ratios are adopted, i.e., R/W = 1.25, 2.5, 3.75, 5, and 6.25. The results indicate that an improvement up to 10% in overall film cooling effectiveness can be achieved with smaller fillet radii. However, this effect diminishes as the fillet radius increases and becomes negative at R/W = 6.25. By examining the contours of the film cooling effectiveness, a prominent inclined strip can be observed across the blade passage. The analysis indicates that the pressure-side leg horseshoe vortex is the primary factor contributing to the variation in the film cooling performance. Furthermore, the film cooling effectiveness can be slightly improved near the suction side of the blade leading edge as the result of the suppression of endwall separation in this region. The rim seal slot filleting eliminates the slot leakage separation, which, in turn, expedites the endwall cooling flow. Eventually, pressure-side leg horseshoe vortex is weakened and the performance of the film cooling is improved. As the fillet radius continues to increase, the through-flow area for the cooling flow enlarges, resulting in a gradual decrease in the film cooling performance. (c) 2025 Author(s).

关键词： Vortex flow

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