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Journal of Hydrodynamics 2023年第5期35卷 942-953页

作者： Xiang-qing Zhang Xiao-fei Zhang Xu Qiu Dan Gao Yu-ning Zhang Key Laboratory of Power Station Energy Transfer Conversion and System(Ministry of Education) School of Energy Power and Mechanical EngineeringNorth China Electric Power UniversityBeijing102206China China Atomic Energy Publishing and Media Co.LTD Beijing100048China China Institute of Nuclear Industry Strategy Beijing100048China National Institute of Energy Development Strategy North China Electric Power UniversityBeijing102206China

Based on high-speed photographic experiments,this study presents a detailed qualitative and quantitative analysis of the dynamics of a single cavitation bubble near the Boundary of a rigid wall in asymmetric settings.The main findings are reported as follows:(1)The non-sphericity of the bubble interface decreases with increasing spacing between the bubble and the Boundary,and the asymmetry of the bubble becomes more significant with increasing asymmetry angle.(2)The motion mode of the bubble cluster in the second oscillation cycle can be divided into two typical modes depending on the direction of movement.(3)The angle between the oblique jet pointing towards the upper wall surface and the horizontal direction in the second oscillation cycle decreases as the dimensionless spacing decreases.

关键词： Asymmetry Boundary cavitation bubble high-speed photography jet non-sphericity

Evolution of Boundary layer ozone in Shijiazhuang,a suburban site on the North China Plain

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Journal of Environmental Sciences 2019年第9期31卷 152-160页

作者： Wei Zhao Guiqian Tang Huan Yu Yang Yang Yinghong Wang Lili Wang Junlin An Wenkang Gao Bo Hu Mengtian Cheng Xingqin An Xin Li Yuesi Wang Nanjing University of Information Science and Technology Nanjing 210044 China State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry fLAPC) Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029 China Key Laboratory of Atmospheric Chemistry China Meteorological Administration Beijing 100081 China Department of Atmospheric Science School of Environmental Studies China University of Geosciences Wuhan 430074 China Weather Modification Office of Hebei Province Shijiazhuang 050021 China Key Laboratory of Meteorological Disaster Ministry ofEducation (KLME) Joint International Research Laboratory of Climate and Environment Change (ILCEC) Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters Key Laboratory for Aerosol-Cloud- Precipitation of China Meteorological Administration Nanjing University of Information Science and Technology Nanjing 210044 China Center for Excellence in Regional Atmospheric Environment Institute of Urban Environment Chinese Academy of Sciences Xiamen 361021 China University of Chinese Academy of Sciences Beijing 100049 China

The structure of the Boundary layer affects the evolution of ozone(O3), and research into this structure will provide important insights for understanding photochemical pollution.In this study, we conducted a one-month observation(from June 15 to July 14, 2016) of the Boundary layer meteorological factors as well as O3 and its precursors in Luancheng County,Shijiazhuang(37°53′N, 114°38′E). Our research showed that photochemical pollution in Shijiazhuang is serious, and the mean hourly maximum and mean 8-hr maximum O3 concentrations are 97.9 ± 26.1 and 84.4 ± 22.4 ppbV, respectively. Meteorological factors play a significant role in the formation of O3. High temperatures and southeasterly winds lead to elevated O3 values, and at moderate relative humidity(40%–50%) and medium Boundary layer heights(1200–1500 m), O3 production sensitivity occurred in the transitional region between volatile organic compounds(VOC) and nitrogen oxides(NOx) limitations,and the O3 concentration was the highest. The vertical profiles of O3 were also measured by a tethered balloon. The results showed that a large amount of O3 was stored in the residual layer, and the concentration was positively correlated with the O3 concentration measured the previous day. During the daytime of the following day, the contribution of O3 stored in the residual layer to the Boundary layer reached 27%± 7% on average.

关键词： Ozone Boundary layer Residual layer Vertical evolution Sensitivity

Effects of surface shapes on properties of turbulent/non-turbulent interface in turbulent Boundary layers

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Science China(Technological Sciences) 2020年第2期63卷 214-222页

作者： WU Di WANG JinJun CUI GuangYao PAN Chong Fluid Mechanics Key Laboratory of Education Ministry Beijing University of Aeronautics and AstronauticsBeijing 100191China

The effects of directional riblets surfaces on the turbulent/non-turbulent(T/NT) interface in turbulent Boundary layers are experimentally investigated using two-dimensional time-resolved particle image velocimetry(PIV). The velocity field of streamwise-wall-normal plane for the smooth surface, converging and diverging riblets surfaces are measured. The interface is detected using the criterion of local kinetic energy. The statistical properties of interface height and conditional averaged velocity for different surfaces are analyzed. It is shown that, the converging and diverging riblets surfaces have little effect on the fractal dimension of the T/NT interface, but they cause the intermittency profile deviate from error function and the probability distribution of interface height deviate from Gaussian function. To be specific, the distribution of interface height for the converging riblets surface shows a positive skewness while it shows a negative skewness for the diverging riblets surface.Moreover, the conditional averaged streamwise velocity and spanwise vorticity across the interface are analyzed, and it is found that their self-similarities are preserved for different surfaces when normalized with respective friction velocity. The correlation analysis reveals that near-wall streamwise velocity fluctuation and interface height show a negative correlation.

关键词： riblets surface turbulent Boundary layers turbulent/non-turbulent(T/NT)interface conditional averaging

A new solution to estimate the time delay on the topographic site using time domain 3D Boundary element method

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Earthquake Engineering and Engineering Vibration 2020年第3期19卷 611-623页

作者： Reza Tarinejad Mohsen Isari Abdollah Sohrabi-Bidar Faculty of Civil Engineering University of TabrizTabrizIran School of Geology College of ScienceUniversity of TehranTehranIran

This study focuses on investigating spatial variation of ground motion that has great influence on the dynamic behavior of the large structures located on the surface topography.One of the most effective parameters on the spatial variation of ground motion is the difference between the arrival time of seismic waves in different points located on the abutments.In this research,a three-dimensional model of the Pacoima Dam site is prepared.The time domain 3 D Boundary element method is used to apply non-uniform excitation at the dam supports.This model is subjected to vertically propagating incident SH and P waves.The time delay can be characterized by calculating the value of the time delay for which the cross-correlation between two records is maximized.Finally,to obtain the time delay in a topographic site,a function considering effective parameters such as the height from the canyon base,wave velocity and predominant frequency,is presented.Furthermore,a code was developed for generating the spatially variation of seismic ground motions.The results show that the proposed functions have an acceptable accuracy in estimating the time delay to generate non-uniform ground motion.

关键词： delay Boundary element

Controlling the strength of Zr(10 1 2) grain Boundary by nonmetallic impurities doping: A DFT study

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Journal of Materials Science & Technology 2020年第1期36卷 140-148页

作者： Zhe Xue Xinyu Zhang Jiaqian Qin Mingzhen Ma Riping Liu State Key Laboratory of Metastable Materials Science and Technology Yanshan UniversityQinhuangdao 066004China Metallurgy and Materials Science Research Institute Chulalongkorn UniversityBangkok 10330Thailand

Impurity segregation even small amounts,can drastically change the cohesive properties of the grain boundaries(GB),eventually leading to intergranular embrittlement and failure of the materials,thereby effectively controlling the types and the concentrations of the impurity is very important.In this work,the nonmetallic impurities(C,H,O,N) segregation and their effects on the strength of Zr(10 1 2) GB were thoroughly investigated using first-principles calculations based on density functional theory.A comprehensive analysis of the interstitial configurations and the relative site energies indicating that C,N and O overwhelmingly prefer the octahedral sites,only H,prefers to reside in the tetrahedral sites.Moreover,the strengthening/embrittlement potency of impurity atoms on the GB was estimated using both the Rice-Wang model and first-principles tensile test calculations.The results show that all impurities,exhibit a strong segregation tendency near the GB region.The segregation of C,N and O has a remarkable strengthening effect on strength of the GB,whereas the presence of impurity H weaken the GB.Most importantly,the underlying mechanism of the strength change of the GBs due to the segregation of impurities was profoundly discussed by charge density and the bond lengths analyses,revealing that the strengthening effect especially for C-doped GB,mainly comes from an enhancement of the charge density across the GB plane.In the end,we expect that our results will be certainly useful for future theoretical and experimental investigations on Zr and its alloys.

关键词： Grain Boundary Impurity segregation Strengthening Embrittlement First-principles calculations

Interaction mechanisms of shock waves with the Boundary layer and wakes in a highly-loaded NGV using hybrid RANS/LES

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Chinese Journal of Aeronautics 2020年第1期33卷 149-160页

作者： Xiutao BIAN Qingsong WANG Xinrong SU Xin YUAN Key Laboratory for Thermal Science and Power Engineering of Ministry of Education Tsinghua UniversityBeijing 100084China

Accurate predictions of Shock Waves and Boundary Layer Interaction(SWBLI)and strong Shock Waves and Wake Vortices Interaction(SWWVI)in a highly-loaded turbine propose challenges to the currently widely used Reynolds-Averaged Navier-Stokes(RANS)model.In this work,the SWBLI and the SWWVI in a highly-loaded Nozzle Guide Vane(NGV)are studied using a hybrid RANS/LES strategy.The Turbulence Kinetic Energy(TKE)budget and the Proper Orthogonal Decomposition(POD)method are used to analyze flow mechanisms.Results show that this hybrid RANS/LES method can obtain detailed flow structures for flow mechanisms analysis.Strong shock waves induce Boundary layer separation,while the presence of a separation bubble can in turn lead to a Mach reflection phenomenon.The shock waves cause trailing-edge vortices to break clearly,and the wakes,in turn,can change the shocks intensity and direction.Furthermore,the Entropy Generation Rate(EGR)is used to analyze the irreversible loss.It turns out that the SWWVI can reduce the flow field loss.There are several weak shock waves in the NGV flow field,which can increase the irreversible loss.This work offers flow mechanisms analysis and presents the EGR distribution in SWBLI and SWWVI areas in a transonic turbine blade.

关键词： Boundary layer Hybrid RANS/LES NGV Shock waves Wakes

A study on periodic Boundary condition in direct numerical simulation for gas–solid flow

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Chinese Journal of Chemical Engineering 2020年第1期28卷 236-241页

作者： Shiwen Liu Xiaowen Liu Feiguo Chen Limin Wang Wei Ge State Key Laboratory of Multiphase Complex Systems Institute of Process EngineeringChinese Academy of SciencesBeijing 100190China School of Chemical Engineering University of Chinese Academy of SciencesBeijing 100049China

Direct numerical simulation(DNS) of gas–solid flow at high resolution has been carried out by coupling the lattice Boltzmann method(LBM) for gas flow and the discrete element method(DEM) for solid particles. However,the body force periodic Boundary condition(FPBC) commonly used to cut down the huge computational cost of such simulation has faced accuracy concerns. In this study, a novel two-region periodic Boundary condition(TPBC) is presented to remedy this problem, with the flow driven in the region with body force and freely evolving in the other region. With simulation cases for simple circulating fluidized bed risers, the validity and advantages of TPBC are demonstrated with more reasonable heterogeneity of the particle distribution as compared to the corresponding case with FPBC.

关键词： Direct numerical simulation Periodic Boundary condition Two-region periodic Boundary condition Gas–solid flow Heterogeneity

Numerical and experimental investigation into hypersonic Boundary layer transition induced by roughness elements

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Chinese Journal of Aeronautics 2019年第3期32卷 559-567页

作者： Hao DONG Shicheng LIU Xi GENG Song LIU Liming YANG Keming CHENG Department of Aerodynamics Nanjing University of Aeronautics and Aeronautics Department of Mechanical Engineering National University of Singapore

In this work, the Direct Numerical Simulation(DNS) and Oil-Film Interferometry(OFI)technique are used to investigate the hypersonic Boundary layer transition induced by single and double roughness elements at Mach number 5. For single roughness, the DNS results showed that both horseshoe vortices and hairpin vortices caused by shear layer instability can affect the Boundary layer instability. The generation of the near-wall unstable structure is the key point of Boundary layer transition behind the roughness element. At the downstream of the roughness element, the interaction between horseshoe vortices and hairpin vortices will spread in the spanwise direction.For double roughness elements, the effect of the spacing between roughness elements on the transition is studied. It is found that the case of higher spacing between roughness elements is more effective for inducing transition than the lower one. The interaction between two adjacent roughness elements can suppress the evolution of horseshoe vortices in the downstream and trigger the instability of shear layer. Thus, the transition will be suppressed accordingly.

关键词： Boundary layer transition Hypersonic Direct numerical simulation (DNS) Oil-film interferometry Roughness elements

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反映南海U形海疆线的《南洋群岛新地图》

科学通报 2019年第23期64卷 2390-2394页

作者：骆遥李敬敏张文志刘诗华中国自然资源航空物探遥感中心北京100083

唐丹玲等人[1]发现1951年光华舆地学社编制的《中华人民共和国新地图》(第二版)以连续国界线方式绘制南海诸岛地图,明确了南海的管辖权,并建议以'南海U形海疆线'表征我国南海的海疆线.为了深化对南海U形海疆线的认识,在此特补充文献中... 详细信息

唐丹玲等人[1]发现1951年光华舆地学社编制的《中华人民共和国新地图》(第二版)以连续国界线方式绘制南海诸岛地图,明确了南海的管辖权,并建议以'南海U形海疆线'表征我国南海的海疆线.为了深化对南海U形海疆线的认识,在此特补充文献中极少提及的《南洋群岛新地图》(Map of East Indies)[2]并附讨论.

关键词： South China Sea Islands Map of East Indies U-Boundary international Boundary

CmBES1 is a regulator of Boundary formation in chrysanthemum ray florets

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Horticulture Research 2020年第1期7卷 1097-1108页

作者： Peilei Cheng Yanan Liu Yiman Yang Hong Chen Hua Cheng Qian Hu Zixin Zhang Jiaojiao Gao Jiaxin Zhang Lian Ding Weimin Fang Sumei Chen Fadi Chen Jiafu Jiang State Key Laboratory of Crop Genetics and Germplasm Enhancement Key Laboratory of LandscapingMinistry of Agriculture and Rural AffairsCollege of HorticultureNanjing Agricultural University210095 NanjingChina

Chrysanthemum(Chrysanthemum morifolium)is an ideal model species for studying petal morphogenesis because of the diversity in the flower form across varieties;however,the molecular mechanisms underlying petal development are poorly understood.Here,we show that the brassinosteroid transcription factor BRI1-EMS-SUPPRESSOR 1(CmBES1)in chrysanthemum(C.morifolium cv.Jinba)is important for organ Boundary formation because it represses organ Boundary identity genes.Chrysanthemum plants overexpressing CmBES1 displayed increased fusion of the outermost ray florets due to the loss of differentiation of the two dorsal petals,which developed simultaneously with the ventral petals.RNA-seq analysis of the overexpression lines revealed potential genes and pathways involved in petal development,such as CUP-SHAPED COTYLEDON(CUC2),CYCLOIDEA 4(CYC4),genes encoding MADS-box transcription factors and homeodomain-leucine zippers(HD-Zips)and auxin pathway-related genes.This study characterizes the role of CmBES1 in ray floret development by its modulation of flower development and Boundary identity genes in chrysanthemum.

关键词： genes Boundary expressing