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Numerical simulation of flow field deposition and erosion characteristics around bridge-road transition section

Journal of Mountain Science 2024年第5期21卷 1491-1508页

作者： ZHANG Kai WANG Zhenghui WANG Tao TIAN Jianjin ZHANG Hailong LIU Yonghe College of Civil Engineering Lanzhou Jiaotong UniversityLanzhou 730000China Key Laboratory of Desert and Desertification Northwest Institute of Eco-Environment and ResourcesChinese Academy of SciencesLanzhou 730000China

Wind-sand flow generates erosion and deposition around obstacles such as bridges and roadbeds, resulting in sand damage and endangering railway systems in sandy regions. Previous studies have mainly focused on the flow field around roadbeds, overlooking detailed examinations of sand particle erosion and deposition patterns near bridges and roadbeds. This study employs numerical simulations to analyze the influence of varying heights and wind speeds on sand deposition and erosion characteristics at different locations: the bridge-road transition section(side piers), middle piers, and roadbeds. The results show that the side piers, experience greater accumulation than the middle piers. Similarly, the leeward side of the roadbed witnesses more deposition compared to the windward side. Another finding reveals a reduced sand deposition length as the vertical profile, in alignment with the wind direction, moves further from the bridge abutments at the same clearance height. As wind speeds rise, there’s a decline in sand deposition and a marked increase in erosion around the side piers, middle piers and roadbeds. In conclusion, a bridge clearance that’s too low can cause intense sand damage near the side piers, while an extremely high roadbed may lead to extensive surface sand deposition. Hence, railway bridges in areas prone to sandy winds should strike a balance in clearance height. This research provides valuable guidelines for determining the most suitable bridge and roadbed heights in regions affected by wind and sand.

关键词： Sandstorm flow field Bridge-road transition section Sedimentation erosion Numerical simulation

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flow field, heat transfer and inclusion behavior in a round bloom mold under effect of a swirling flow submerged entry nozzle

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Journal of Iron and Steel Research(International) 2023年第6期30卷 1211-1221页

作者： Qing-hua Xie Pei-yuan Ni Toshihiro Tanaka Mikael Ersson Ying Li Key Laboratory of Ecological Metallurgy of Multi-metal Intergrown Ores of Ministry of Education School of MetallurgyNortheastern UniversityShenyang 110819LiaoningChina Liaoning Key Laboratory of Metallurgical Sensor Materials and Technology School of MetallurgyNortheastern UniversityShenyang 110819LiaoningChina Graduate School of Engineering Osaka UniversityOsaka 565-0871Japan Department of Materials Science and Engineering KTH Royal Institute of TechnologyStockholm 10044Sweden

flow field,heat transfer and inclusion behavior in a 700 mm round bloom mold under the effect of a swirling flow submerged entry nozzle(SEN)were investigated with the aim to enhance the casting process.The results indicate that the impinging flow phenomenon,which is commonly observed in conventional single-port SEN casting,was completely suppressed by the swirling flow SEN coming from a novel swirling flow generator design in tundish.Steel from the SEN port moved towards the mold wall in 360 direction,leading to a uniform temperature distribution in the mold.Compared to a conventional single-port SEN casting,the steel super-heat was decreased by about 5 K at the mold center,and the temperature was increased by around 3.5 K near the meniscus.In addition,the removal ratio of inclusions to the mold top surface in the swirling flow SEN casting was found to be increased.Specifically,the removal ratio of spherical inclusions with diameters of 1,10,50 and 100μm was increased by 18.2%,18.5%,22.6% and 42.7%,respectively.Furthermore,the ratio was raised by 18.2%,20.8%,21.5% and 44.1%for non-spherical inclusions,respectively.

关键词： Large round bloom Swirling flow submerged entry nozzle casting flow field Heat transfer Inclusion behavior

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flow field design and experimental investigation of electrochemical machining on blisk

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Chinese Journal of Aeronautics 2022年第8期35卷 295-303页

作者： Jianwei GUO Dong ZHU Di ZHU College of Mechanical and Electrical Engineering Nanjing University of Aeronautics and AstronauticsNanjing 210016China

flow field is a crucial factor to influence the stability and surface quality in the electrochemical machining(ECM)of blisks.A four-way flow mode was proposed to eliminate mixing regions of electrolyte at the leading and tailing edges.Two flow field models were described separately in this report:a W-shaped flow mode and a four-way flow mode.The flow field was analyzed through a finite element method.The results showed that,in comparison with the W-shaped flow mode,the distribution of electrolyte flow was more uniformed and the mixed region in the flow channel was improved.The pressure of the leading and tailing edges inlets was optimized,and optimal pressure of 0.6 MPa was determined.In addition,verification experiments were performed,and the results showed that the stability,efficiency,and quality of the profiles of the blisk blade manufactured by ECM were enhanced in the new flow mode.

关键词： Blisk Electrochemical machining Electrolyte flow field Surface quality

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Optimization of flow field in electrochemical trepanning of integral cascades(Ti6Al4V)

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Chinese Journal of Aeronautics 2022年第10期35卷 354-364页

作者： Gaopan LEI Dong ZHU Jiabao LI College of Mechanical&Electrical Engineering Nanjing University of Aeronautics and AstronauticsNanjing 210016China

Ti6Al4V is widely applied in the integral cascades of aero engines.As an effective machining method,electrochemical trepanning(ECTr)has unique advantages in processing surface parts made of hard-to-cut materials.In ECTr,the state of the flow field has a significant effect on processing stability and machining quality.To improve the uniformity of the flow field when ECTr is applied to Ti6Al4V,two different flow modes are designed,namely full-profile electrolyte supply(FPES)and edges electrolyte supply(EES).Different from the traditional forward flow mode,the flow directions of the electrolyte in the proposed modes are controlled by inlet channels.Simulations show that the flow field under EES is more uniform than that under FPES.To further enhance the uniformity of the flow field,the structure of EES is optimized by modifying the insulating sleeve.In the optimized configuration,the longitudinal distance between the center of the inlet hole and the center of the blade is 6.0 mm,the lateral distance between the centers of the inlet holes on both sides is 16.5 mm,the length to which the electrolyte enters the machining area is 1.5 mm,and the height of the insulating sleeve is 13.5 mm.A series of ECTr experiments are performed under the two flow modes.Compared with EES,the blade machined by FPES is less accurate and has poorer surface quality,with a surface roughness(R_(a))of 3.346μm.Under the optimized EES,the machining quality is effectively enhanced,with the surface quality improved from R_(a)=2.621μm to R_(a)=1.815μm,thus confirming the efficacy of the proposed methods.

关键词： Edges electrolyte supply Electrochemical trepanning flow field Structure optimization Surface quality

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A generative deep learning framework for airfoil flow field prediction with sparse data

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Chinese Journal of Aeronautics 2022年第1期35卷 470-484页

作者： Haizhou WU Xuejun LIU Wei AN Hongqiang LYU MIIT Key Laboratory of Pattern Analysis and Machine Intelligence College of Computer Science and TechnologyNanjing University of Aeronautics and AstronauticsNanjing 211106China Key Laboratory of Aerodynamic Noise Control Mianyang 621000China State Key Laboratory of Aerodynamics Mianyang 621000China Collaborative Innovation Center of Novel Software Technology and Industrialization Nanjing 210023China College of Aerospace Engineering Nanjing University of Aeronautics and AstronauticsNanjing 211106China

Deep learning has been probed for the airfoil performance prediction in recent years.Compared with the expensive CFD simulations and wind tunnel experiments,deep learning models can be leveraged to somewhat mitigate such expenses with proper means.Nevertheless,effective training of the data-driven models in deep learning severely hinges on the data in diversity and quantity.In this paper,we present a novel data augmented Generative Adversarial Network(GAN),daGAN,for rapid and accurate flow filed prediction,allowing the adaption to the task with sparse data.The presented approach consists of two modules,pre-training module and fine-tuning module.The pre-training module utilizes a conditional GAN(cGAN)to preliminarily estimate the distribution of the training data.In the fine-tuning module,we propose a novel adversarial architecture with two generators one of which fulfils a promising data augmentation operation,so that the complement data is adequately incorporated to boost the generalization of the model.We use numerical simulation data to verify the generalization of daGAN on airfoils and flow conditions with sparse training data.The results show that daGAN is a promising tool for rapid and accurate evaluation of detailed flow field without the requirement for big training data.

关键词： CFD flow field Generative adversarial networks(GANs) Sparse data Supercritical airfoil

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Mathematical modeling of flow field in slab continuous casting mold considering mold powder and solidified shell with high temperature quantitative measurement

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Journal of Iron and Steel Research(International) 2022年第3期29卷 445-461页

作者： Yi-bo Liu Jian Yang Chao Ma Tao Zhang Fu-bin Gao Tai-quan Li Jun-li Chen State Key Laboratory of Advanced Special Steel School of Materials Science and EngineeringShanghai UniversityShanghai200444China Technology Center HBIS Handan Iron and Steel Group Co.Ltd.Handan56015HebeiChina

Optimization of mathematical model of flow field in slab continuous casting mold was performed by means of industrial measurement and mathematical modeling.The rod deflection method was used to quantitatively measure the velocities near the mold surface at high temperature.The measurement results were compared with the simulation results of three mathematical models at different argon gas flow rates of 6,10 and 14 L min^(−1).The model 1 neglects the mold powder layer,thermal effect and solidified shell.The model 2 only considers the influence of mold powder layer.The model 3 considers the influence of mold powder layer,thermal effect and solidified shell on the flow field.In all three models,the diameter of argon bubbles obeys Rosin-Rammler distribution fitted according to the experimental data of others’previous work.With increasing the argon gas flow rate,the velocity of liquid steel near the mold surface decreases.The model 1 seriously underestimates the shear stress of liquid steel near the mold surface,and its calculation results show higher velocity near the mold surface,lower turbulent kinetic energy and wider distribution of argon gas bubbles in the mold.The simulation results of model 2 only considering the viscous resistance of the mold powder layer to liquid steel makes the velocity near the surface lower than the measurement results obviously.The calculated velocities near the mold surface with model 3 are in best agreement with the measured results,showing the reasonable spatial distribution range of argon bubbles in the mold and the moderate turbulent kinetic energy.In the present conditions,the best argon gas flow rate is 10 L min^(−1) due to the moderate velocity near the mold surface,the appropriate distribution of argon gas bubbles in the mold and the smallest fluctuation amplitude on the mold surface.

关键词： flow field Mold powder layer Solidified shell Rosin-Rammler distribution Mathematical modeling Rod deflection method

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Numerical Simulation of 3D flow field and flow-Induced Noise Characteristics in a T-Shaped Reducing Tee Junction

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Fluid Dynamics & Materials Processing 2023年第6期19卷 1463-1478页

作者： Feiran Lv Min Wang Chuntian Zhe Chang Guo Ming Gao Shandong Engineering Laboratory for High-Efficiency Energy Conservation and Energy Storage Technology&Equipment School of Energy and Power EngineeringShandong UniversityJinan250061China Jinan Motor Vehicle Pollution Control Center Jinan250099China School of Energy and Power Engineering Qilu University of TechnologyJinan250306China

The so-called T-shaped reducing tees are typically used to divide,change and control(to a certain extent)the flow direction in pipe networks.In this study,the Ffowcs Williams–Hawkings(FW-H)equation and the Large Eddy Simulation(LES)methods are used to simulate the flow-induced noise related to T-shaped reducing tees under different inlet flow velocities and for different pipe diameter ratios.The results show that the maximum flow velocity,average flow velocity,and vorticity in the branch pipe increase gradually as the related diameter decreases.Strong vorticity and secondary flows are also observed in the branch pipe,and the associated violent pressure fluctuations are found to be the main sources of flow-induced noise.In particular,as the pipe diameter ratio decreases from 1 to 0.45,the Total Sound Pressure Level(TSPL)increases by 6.8,6.26,and 7.43 dB for values of the inlet flow velocity of 1,2,and 3 m/s,respectively.The distribution characteristics of the flow-induced noise in the frequency domain follow similar trends for different pipe diameter ratios.

关键词： flow field flow-induced noise FW-H equation large-eddy simulation

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Numerical simulation on flow field,wind erosion and sand sedimentation patterns over railway subgrades

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Journal of Mountain Science 2022年第10期19卷 2968-2986页

作者： ZHANG Kai ZHAO Li-ming ZHANG Hai-long GUO Ao-jun YANG Bo LI Sheng College of Civil Engineering Lanzhou Jiaotong UniversityLanzhou 730000China Key Laboratory of Desert and Desertification Northwest Institute of Eco-Environment and ResourcesChinese Academy of SciencesLanzhou 730000China

The railway subgrades in the sandy areas act as an obstacle interfering wind-blown sand,causing sand erosion and sedimentation,which can disrupt the safe and stable operation of the railway system.Most previous studies mainly focus on the flow field around railway subgrades,however,the real erosion and sedimentation patterns are rarely studied.This study aims to analyze the erosion and sand sedimentation patterns of wind-blown sand over the subgrades with different heights and steel rails using the ratio of the wall shear stress to the critical value of erosion shear stress.Results show that wind erosion near the top of the upwind slope of the embankment and the shoulder on the upwind side are more severe,and the severity increases with an increase in the height of the embankment.With the increase of wind velocity,sand sedimentation both on the windward and leeside of the subgrade decreases and wind erosion by reverse flow occur.This study indicates that railways in sandy areas should be constructed with a moderate subgrade height(4 m).

关键词： Numerical simulation flow field Wind erosion Sand sedimentation Railway subgrades Subgrade height

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flow field and dissolved oxygen distributions in the outer channel of the Orbal oxidation ditch by monitor and CFD simulation

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Journal of Environmental Sciences 2013年第4期25卷 645-651页

作者： Xuesong Guo Xin Zhou Qiuwen Chen Junxin Liu Research Center for Eco-Environmental Sciences Chinese Academy of Sciences

In the Orbal oxidation ditch, denitrification is primarily accomplished in the outer channel. However, the detailed characteristics of the flow field and dissolved oxygen （DO） distribution in the outer channel are not well understood. Therefore, in this study, the flow velocity and DO concentration in the outer channel of an Orbal oxidation ditch system in a wastewater treatment plant in Beijing （China） were monitored under actual operation conditions. The flow field and DO concentration distributions were analyzed by computed fluid dynamic modeling. In situ monitoring and modeling both showed that the flow velocity was heterogeneous in the outer channel. As a result, the DO was also heterogeneously distributed in the outer channel, with concentration gradients occurring along the flow direction as well as in the cross-section. This heterogeneous DO distribution created many anoxic and aerobic zones, which may have facilitated simultaneous nitrificafion-denitrification in the channel. These findings may provide supporting information for rational optimization of the performance of the Orbal oxidation ditch.

关键词： computed fluid dynamic dissolved oxygen distribution flow field Orbal oxidation ditch

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A large-scale cold plasma jet: generation mechanism and application effect

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Plasma Science and Technology 2024年第4期26卷 1-8页

作者：崔伟胜张若兵 Shenzhen International Graduate School Tsinghua UniversityShenzhen 518055People’s Republic of China

Atmospheric pressure cold plasma jets(APCPJs) typically exhibit a slender, conical structure,which imposes limitations on their application for surface modification due to the restricted treatment area. In this paper, we introduce a novel plasma jet morphology known as the large-scale cold plasma jet(LSCPJ), characterized by the presence of both a central conical plasma jet and a peripheral trumpet-like diffuse plasma jet. The experimental investigations have identified the factors influencing the conical and the trumpet-like diffuse plasma jet, and theoretical simulations have shed light on the role of the flow field and the electric field in shaping the formation of the LSCPJ. It is proved that, under conditions of elevated helium concentration, the distributions of impurity gas particles and the electric field jointly determine the plasma jet’s morphology. High-speed ICCD camera images confirm the dynamic behavior of plasma bullets in LSCPJ, which is consistent with the theoretical analysis. Finally, it is demonstrated that when applied to the surface treatment of silicone rubber, LSCPJ can achieve a treatment area over 28 times larger than that of APCPJ under equivalent conditions. This paper uncovers the crucial role of impurity gases and electric fields in shaping plasma jet morphology and opens up the possibility of efficiently diversifying plasma jet generation effects through external electromagnetic fields. These insights hold the promise of reducing the generation cost of plasma jets and expanding their applications across various industrial sectors.

关键词： diffuse plasma jet flow field electric field surface treatment

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