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Investigation on subsurface vortices within a closed pump intake under different pressure conditions

Journal of Hydrodynamics 2020年第5期32卷 914-928页

作者： Miao Guo xue-lin tang Xiao-qin Li Fu-jun Wang Xiao-yan Shi College of Water Resources and Civil Engineering China Agricultural UniversityBeijing 100083China Beijing Engineering Research Centre of Safety and Energy Saving Technology for Water Supply Network System China Agricultural UniversityBeijing 100083China

An experimental study to investigate various features of subsurface vortices and their evolutions inside a closed pump intake under different pressure conditions at free surface,and to analyze the influence of a pipe bell with different mean axial velocities at the same water level on flow patterns is *** all cases,three different flow regimes are closely observed:various side-wall attached,back-wall attached and submerged vortices structures,and their evolutions are subject to the free-surface pressure for a critical flow rate,the number and strength of all these vortex rise as the absolute value of the pressure increases for a higher flow rate,for a lower flow rate,whether the side-wall vortices occur or not is related closely to the pressure magnitude,and there are no vortices for lower absolute pressure values,the number and the strength of the side-wall vortices increase as the absolute pressure values ***,based on statistical analyses,the side-wall vortex probability on the right side along the stream-wise direction is much higher than that on the opposite side for all operation cases,particularly single vortex probability,and the back-wall vortex probabilities are quite higher with values of more than 90%,meanwhile,the multi-vortices probability is much higher than that of the *** captured vortices have been qualitatively classified into different“vortex zones”:no vortex zones and vortex zones including transition,single-and *** Reynolds number and the absolute value pressure are the most important parameters which influence the existence and the number of these vortices,and the increase of the two parameters reduces the no vortex transition zone and causes bigger difference in the back-wall and side-wall vortex zones.

关键词： Evolution of subsurface vortices particle-image velocimetry(PIV) vortex probability closed pump intake

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Pressure fluctuation characteristics in the pressurization unit of a multiphase pump

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Journal of Hydrodynamics 2021年第6期33卷 1230-1241页

作者： Guang-tai Shi Zong-ku Liu Ye-xiang Xiao xue-lin tang Xiao-bing Liu Key Laboratory of Fluid and Power Machinery Ministry of EducationXihua UniversityChengdu 610039China College of Water Resources and Civil Engineering China Agricultural UniversityBeijing 100083China State Key Laboratory of Hydroscience and Engineering and Department of Energy and Power Engineering Tsinghua UniversityBeijing 100084China Beijing Engineering Research Centre of Safety and Energy Saving Technology for Water Supply Network System China Agricultural UniversityBeijing 100083China

The tip clearance induces the tip leakage vortex(TLV),which has a great impact on the pressure fluctuation characteristics of the multiphase *** investigate the effect of the tip clearance on the pressure fluctuations,based on the Reynolds time-averaged Navier-Stokes equation and the shear stress transfer(SST)k-ωturbulence model,the three-dimensional turbulent flow in the pump is numerically simulated for different tip clearances in the water and gas-liquid two-phase cases by using the ANSYS CFX software and the results are verified with experimental *** is shown the greater pressure fluctuation intensity corresponds with the TLV both in the water and gas-liquid two-phase *** the meantime,the location of the maximum pressure fluctuation intensity is related to the tip clearance *** addition,for different tip clearances,the pressure fluctuation intensity with the rotor and stator interaction(RSI)is relatively *** difference is that when R_(tc)=1.5 mm,the pressure fluctuation intensity near the impeller middle point is also relatively *** the whole,the pressure fluctuation intensity in the gas-liquid two-phase case is larger than that in the water ***,the gas causes the frequency of the high-amplitude pressure fluctuation in the impeller and the diffuser to be shifted from 7 f_(n)(f_(n) denotes impeller rotational frequency)and 3 f_(n) to the low-frequency region,*** pressure fluctuations at the blade-passing frequency(BPF)and the multiple BPFs gradually ***,the amplitude at the dominant frequency in the gas-liquid two-phase case is at least one order of magnitude smaller than that in the water case,and the peak-to-peak value of the pressure fluctuation is also much smaller.

关键词： Multiphase pump gas void faction pressure fluctuation intensity tip leakage vortex(TLV) numerical simulation

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Optimization of the co-closing law of guide vanes and blades for bulb turbines based on CFD

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Journal of Hydrodynamics 2024年第2期36卷 363-377页

作者： Hui Liu Yun-fa lin Yong-guang Cheng Song xue Mao-jia tang Jian Zhang Jia-yi Fan State Key Laboratory of Water Resources Engineering and Management Wuhan UniversityWuhan430072China Dongfang Electric Machinery Co. Ltd.Deyang618000China

The load rejection transient process of bulb turbine units is critical to safety of hydropower stations,and determining appropriate closing laws of guide vanes(GVs)and runner blades(RBs)for this process is of *** this study,we proposed a procedure to optimize the co-closing law of GVs and RBs by using computational fluid dynamics(CFD),combined with the design of experiment(DOE)method,approximation model,and genetic optimization *** sensitivity of closing law parameters on the histories of head,speed,and thrust was analyzed,and a two-stage GVs’closing law associating with a linear RBs’closing law was *** results show that GVs dominate the transient characteristics by controlling the change of *** GVs’first-stage closing speed while shortening first-stage closing time can not only significantly reduce the maximum rotational speed but also suppress the water hammer pressure;slowing GVs’second-stage closing speed is conducive to controlling the maximum reverse axial *** directly affect the runner *** RBs’closing speed can further reduce the rotational speed and the maximum reverse axial *** safety margin of each control parameter,flow patterns,and pressure pulsations of a practical hydropower station were all improved after optimization,demonstrating the effectiveness of this method.

关键词： Bulb turbine load rejection transient process double regulation closing law optimization computational fluid dynamics(CFD)

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Granular collapse in fluids:Dynamics and flow regime identification

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Particuology 2024年第9期92卷 30-41页

作者： Hu tang Bisong lin Dengming Wang Department of Mechanics and Engineering Science School of Civil Engineering and MechanicsKey Laboratory of Mechanics on Disaster and Environment in Western China of Ministry of EducationLanzhou UniversityLanzhou730000China

The collapse of granular material in fluids is a prevalent phenomenon in both natural and industrial processes,displaying a notable sensitivity to initial configuration of the *** study is specifically oriented towards falling process of collapsing material under various fluid conditions,employing the computational fluid dynamics-discrete element method(CFD-DEM)to primarily investigate the dynamics and scaling laws of deposit morphology of collapsed *** a comprehensive analysis of particle sedimentation in fluids,we introduce a refined inertial characteristic time for granular collapse within the inertial ***,we propose modifications to conventional fluid-particle density ratio and Reynolds number,aiming to enhance the accuracy of depicting collapse dynamics and identifying flow regimes across diverse column heights and fluid ***,we construct a phase diagram of flow regimes using modified dimensionless numbers,emphasizing the role of column height in transition between viscous and inertial *** parameters demonstrate enhanced relevance in governing the collapse of immersed granular columns,thereby contributing to a more nuanced understanding of fluid-particle interations in dense granular flows under different regimes.

关键词： Immersed granular material Collapse Dynamic Flow regime Computational fluid dynamics-discrete element method

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Improved catalytic performance of CO_(2) electrochemical reduction reaction towards ethanol on chlorine-modified Cu-based electrocatalyst

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Nano Research 2024年第5期17卷 3761-3768页

作者： Yifan Liu Hehua tang Yitian Zhou Bo-lin lin School of Physical Science and Technology ShanghaiTech UniversityShanghai 201210China

Effective electrochemical conversion of CO_(2) to value-added liquid multi-carbon products driven by renewable energy is a promising approach to alleviate excessive CO_(2) emission and achieve large-scale renewable energy ***,the selectivity and catalytic activity towards liquid multi-carbon products of CO_(2) electroreduction reaction are still unsatisfactory due to the sluggish C-C coupling process and the formation of complex oxygen-containing ***,designing and fabricating highly effective electrocatalysts is crucial for practical applications in this ***,we developed Cl-modified Cu catalyst(Cu-Cl)for efficient electrochemical reduction of CO_(2) to *** optimal Faradaic efficiency and partial current density of ethanol on the Cu-Cl sample reached 26.2%and 343.2 mA·cm^(-2) at-0.74 V(*** hydrogen electrode(RHE)),which were 1.66 and 1.76 times higher than those of the catalyst without Cl decoration,outperforming those in most previously reported *** functional theory(DFT)calculations revealed that the Cl-modified Cu surface suppressed the parasitic hydrogen evolution reaction(HER)and reduced the energy barrier for the C-C coupling process,making the formation of key intermediates favorable for ethanol ***,the decoration of Cl on the Cu surface facilitated ethanol formation.

关键词： CO_(2)electrochemical reduction halogen chlorine Cu-based catalysts ethanol multi-carbon products

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Relationships between Terrain Features and Forecasting Errors of Surface Wind Speeds in a Mesoscale Numerical Weather Prediction Model

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Advances in Atmospheric Sciences 2024年第6期41卷 1161-1170页

作者： Wenbo xue Hui YU Shengming tang Wei HUANG Chinese Academy of Meteorological Sciences Beijing 100081China University of Chinese Academy of Sciences Beijing 101408China Shanghai Typhoon Institute/CMA Shanghai 200030China Key Laboratory of Numerical Modeling for Tropical Cyclone/CMA Shanghai 200030China

Numerical weather prediction(NWP)models have always presented large forecasting errors of surface wind speeds over regions with complex *** this study,surface wind forecasts from an operational NWP model,the SMS-WARR(Shanghai Meteorological Service-WRF ADAS Rapid Refresh System),are analyzed to quantitatively reveal the relationships between the forecasted surface wind speed errors and terrain features,with the intent of providing clues to better apply the NWP model to complex terrain *** terrain features are described by three parameters:the standard deviation of the model grid-scale orography,terrain height error of the model,and slope *** results show that the forecast bias has a unimodal distribution with a change in the standard deviation of *** minimum ME(the mean value of bias)is 1.2 m s^(-1) when the standard deviation is between 60 and 70 m.A positive correlation exists between bias and terrain height error,with the ME increasing by 10%−30%for every 200 m increase in terrain height *** ME decreases by 65.6%when slope angle increases from(0.5°−1.5°)to larger than 3.5°for uphill winds but increases by 35.4%when the absolute value of slope angle increases from(0.5°−1.5°)to(2.5°−3.5°)for downhill *** sensitivity experiments are carried out with a model output statistical(MOS)calibration model for surface wind speeds and ME(RMSE)has been reduced by 90%(30%)by introducing terrain parameters,demonstrating the value of this study.

关键词： surface wind speed terrain features error analysis MOS calibration model

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Manipulating d-d orbital hybridization induced by Mo-doped Co_(9)S_(8) nanorod arrays for high-efficiency water electrolysis

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Journal of Energy Chemistry 2024年第6期93卷 592-600,I0015页

作者： xue Zhou Jing Li Guangyao Zhou Weiran Huang Yucan Zhang Jun Yang Huan Pang Mingyi Zhang Dongmei Sun Yawen tang lin Xu Jiangsu Key Laboratory of New Power Batteries Jiangsu Collaborative Innovation Centre of Biomedical Functional MaterialsSchool of Chemistry and Materials ScienceNanjing Normal UniversityNanjing 210023JiangsuChina 'College of Science Jinling Institute of TechnologyNanjing 211169JiangsuChina State Key Laboratory of Multiphase Complex Systems Institute of Process EngineeringChinese Academy of SciencesBeijing 100190China Nanjing IPE Institute of Green Manufacturing Industry Nanjing 211100JiangsuChina School of Chemistry and Chemical Engineering Yangzhou UniversityYangzhou 225009JiangsuChina Key Laboratory for Photonic and Electronic Bandgap Materials Ministry of EducationSchool of Physics and Electronic EngineeringHarbin Normal UniversityHarbin 150025HeilongjiangChina

Precisely refining the electronic structure of electrocatalysts represents a powerful approach to further optimize the electrocatalytic ***,we demonstrate an ingenious d-d orbital hybridization concept to construct Mo-doped Co_(9)S_(8) nanorod arrays aligned on carbon cloth(CC)substrate(abbreviated as Mo-Co_(9)S_(8)@CC hereafter)as a high-efficiency bifunctional electrocatalyst toward water *** has experimentally and theoretically validated that the 4d-3d orbital coupling between Mo dopant and Co site can effectively optimize the H_(2)O activation energy and lower H^(*)adsorption energy barrier,thereby leading to enhanced hydrogen evolution reaction(HER)and oxygen evolution reaction(OER)*** to the unique electronic and geometrical advantages,the optimized Mo-Co_(9)S_(8)@CC with appropriate Mo content exhibits outstanding bifunctional performance in alkaline solution,with the overpotentials of 75 and 234 mV for the delivery of a current density of 10 mA cm^(-2),small Tafel slopes of 53.8 and 39.9 mV dec~(-1)and long-term stabilities for at least 32 and 30 h for HER and OER,*** impressively,a water splitting electrolylzer assembled by the self-supported Mo-Co_(9)S_(8)@CC electrode requires a low cell voltage of 1.53 V at 10 mA cm^(-2)and shows excellent stability and splendid reversibility,demonstrating a huge potential for affordable and scalable electrochemical H_(2) *** innovational orbital hybridization strategy for electronic regulation herein provides an inspirable avenue for developing progressive electrocatalysts toward new energy systems.

关键词： d-d orbital hybridization Transition metal sulfides Nanorods arrays Water electrolysis

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A Numerical Calculation Algorithm of the Inclination Function Based on the Representation of SO(3) Group

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Acta Mathematicae Applicatae Sinica 2024年第1期40卷 137-148页

作者： Yu-xiao Wei Wen-lin tang Department of Geophysics School of Geology Engineering and GeomaticsChang’An UniversityXi’an710064China Key Laboratory of Electronics and Information Technology for Space Systems National Space Science CenterChinese Academy of SciencesBeijing100190China

In the determination of the Earth gravity field in satellite geodesy, the inclination functions represent the projection of data observed along the orbital plane of a satellite orbit into the sphere in the terrestial reference frame. The inclination functions in this work is studied from a group theoretical perspective. The inclination functions are proved to generate a representation of the SO(3) group. An orthogonal relation of the inclination functions is derived and some recurrence relations for the inclination functions are given, based on which an algorithm to calculate the inclination functions is proposed.

关键词： SO(3)group inclination function satellite geodesy representation of SO(3)

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Flexible and Robust Functionalized Boron Nitride/Poly(p‑Phenylene Benzobisoxazole)Nanocomposite Paper with High Thermal Conductivity and Outstanding Electrical Insulation

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Nano-Micro Letters 2024年第2期16卷 423-437页

作者： lin tang Kunpeng Ruan Xi Liu Yusheng tang Yali Zhang Junwei Gu Chongqing Key Laboratory of Green Synthesis and Applications College of ChemistryChongqing Normal UniversityChongqing 401331People’s Republic of China Shaanxi Key Laboratory of Macromolecular Science and Technology School of Chemistry and Chemical EngineeringNorthwestern Polytechnical UniversityXi’an 710072People’s Republic of China

With the rapid development of 5G information technology,thermal conductivity/dissipation problems of highly integrated electronic devices and electrical equipment are becoming *** this work,“high-temperature solid-phase&diazonium salt decomposition”method is carried out to prepare benzidine-functionalized boron nitride(m-BN).Subsequently,m-BN/poly(pphenylene benzobisoxazole)nanofiber(PNF)nanocomposite paper with nacremimetic layered structures is prepared via sol–gel film transformation *** obtained m-BN/PNF nanocomposite paper with 50 wt%m-BN presents excellent thermal conductivity,incredible electrical insulation,outstanding mechanical properties and thermal stability,due to the construction of extensive hydrogen bonds andπ–πinteractions between m-BN and PNF,and stable nacre-mimetic layered ***λ∥andλ_(⊥)are 9.68 and 0.84 W m^(-1)K^(-1),and the volume resistivity and breakdown strength are as high as 2.3×10^(15)Ωcm and 324.2 kV mm^(-1),***,it also presents extremely high tensile strength of 193.6 MPa and thermal decomposition temperature of 640°C,showing a broad application prospect in high-end thermal management fields such as electronic devices and electrical equipment.

关键词： Poly(p-phenylene-2,6-benzobisoxazole)nanofiber Boron nitride Thermal conductivity Electrical insulation

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Environment-adaptive phase-separation-porous fluorofilm for highperformance passive radiation cooling

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Nano Research 2024年第6期17卷 5636-5644页

作者： Weiming tang Yong Li xue Meng Shutao Wang Ziguang Zhao School of Future Technology University of Chinese Academy of SciencesBeijing 100049China CAS Key Laboratory of Bio-inspired Materials and Interfacial Science Technical Institute of Physics and ChemistryChinese Academy of SciencesBeijing 100190China CAS Key Laboratory of Cryogenics Technical Institute of Physics and ChemistryChinese Academy of SciencesBeijing 100190China

Passive radiative cooling is widely recognized as an environmentally sustainable method for achieving significant cooling ***,the mechanical properties and environmental adaptability of current radiative cooling materials are not sufficient to maintain high cooling performance in external *** we reported an environment-adaptive phase-separation-porous fluorofilm for high-performance passive radiation *** to the homogenous fluoro-porous network with limited scattering efficiencies,we modulated the porous structure of the fluorofilm to achieve a strong emissivity of 95.2%(8-13μm)and a high reflectivity of 97.1%(0.3-2.5μm).The fluorofilm demonstrates a temperature drop of 10.5°C and an average cooling power of 81 W·m^(−2)under a sunlight power of 770 W·m^(−2).The high mechanical performance and environmental adaptability of fluorofilms are also *** its significant radiative cooling capability and robust environmental adaptability,the fluorofilm is expected to have a promising future in radiative temperature regulation.

关键词： fluorofilm passive radiation cooling porous optimization thermal regulation

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