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Numerical simulation of ski-jump jet motion using lattice Boltzmann method

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Science China(Technological Sciences) 2011年第S1期54卷 72-75页

作者： zhang Hua 1 &zhang XiaoDong 2 1 School of Renewable Energy,north China {3. power university,beijing 102206,China 2 School of Energy power and Mechanical engineering,north China {3. power university,beijing 102206,China 1. School of Renewable Energy North China Electric Power University Beijing 102206 China 2. School of Energy power and Mechanical engineering North China Electric Power University Beijing 102206 China

Based on the lattice Boltzmann method,a lattice Boltzmann(LB) model of the ski-jump jet two-phase flow is developed first and the corresponding boundary conditions are studied.A simple case study of a droplet horizontal movement calculation is carried out to test and verify the model,where level set method is used to track and reconstruct the moving droplet free surface. Then,we numerically simulate a two dimensional flow field of the ski-jump jet with the LB model,derive the moving surface and velocity vector field of the jet *** simulation results are very consistent with the physical *** effectiveness and reliability of the model are demonstrated by the numerical examples.

关键词： ski-jump jet droplet lattice Boltzmann method interface numerical simulation

Reduced analysis and confirmatory research on co-adaptability theoretical solution to conflicting events in construction engineering projects

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Science China(Technological Sciences) 2010年第2期53卷 480-485页

作者： HOU XueLiang1 , LU Mei2 & WANG Kai3.1 School of Business Administration, north China electric power {3., beijing 102206, China 2 department of Construction Management, Tsinghua {3., beijing 100084, China 3.College of Management, beijing Jiaotong {3., beijing 100084, China 1. School of Business Administration North China Electric Power University Beijing 102206 China2. Department of Construction Management Tsinghua University Beijing 100084 China3. College of Management Beijing Jiaotong University Beijing 100084 China

The co-adaptability theoretical solution to conflicting events in construction engineering projects has three problems. First, the transformation of constraint conditions of theoretical solution is very difficult in practical engineering applications; second, some coefficients are difficult to be determined; third, there are overfull circular arithmetic operations involved in it. To resolve these problems, a new method to reduce the theoretical solution complications is proposed. By analyzing the operating mechanism of theoretical solution model, redundancies in the theoretical solution can be eliminated, and the ISM mapping with the co-adaptability solution can be set up. Based on this approach, a procedure to solve practical conflicting events in construction projects is established by replacing characteristic variables with mathematic variables. The research results show that the procedure can replace the co-adaptability theoretical solution effectively and solve practical conflicting events in construction projects.

关键词： construction project conflict theoretical solution reduced analysis ISM confirmatory research

Current distribution and stability of LTS/HTS hybrid superconducting conductors

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Science China(Technological Sciences) 2010年第7期53卷 2000-2007页

作者： GUAN XiaoJin1,2, WANG YinShun1 & ZHOU WeiWei3.1 Key Laboratory of HV and EMC beijing, north China electric {3. university, beijing 102206, China 2 department of Physics, Baoding university, Baoding 071000, China 3.Institute of electrical engineering, Chinese Academy of Sciences, beijing 100190, China 1. Key Laboratory of HV and EMC beijing North China Electric Power University Beijing 102206 China2. Department of Physics Baoding University Baoding 071000 China3. Institute of Electrical Engineering Chinese Academy of Sciences Beijing 100190 China

Current distribution and stability of a hybrid LTS/HTS superconductor, consisting of multifilamentary NbTi/Cu and Bi2223.Ag tapes, were numerically analyzed according to power-law models. The results showed that most of current passed through the LTS and the current increased in the HTS with temperature rise when the transport current was below the critical current of the hybrid conductor. The quench propagation velocity of the hybrid conductor was smaller but its minimum quench energy was larger than those of LTS conductors, indicating that the stability of the hybrid superconducting conductor was effectively improved and a high engineering current density was simultaneously achieved. Finally, a hybrid sample, made by soldering Bi2223.Ag tape onto NbTi/Cu conductor, was prepared and tested successfully at helium temperature. The experimental results qualitatively agreed with the simulated ones.

关键词： distribution hybrid conductor minimum quench energy quench propagation velocity n value stability

Some invariant properties of ordered information systems under homomorphism

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Science China(Information Sciences) 2010年第9期53卷 1816-1825页

作者： WANG ChangZhong1*,CHEN DeGang2 & HU QingHua3.1department of Mathematics,Bohai university,Jinzhou 121000,China 2department of Mathematics and Physics,{3. China electric power university,beijing 102206,China 3.5} engineering,Harbin Institute of Technology,Harbin 150001,China 1. department of Mathematics Bohai University Jinzhou 121000 China2. Department of Mathematics and Physics North China Electric Power University Beijing 102206 China3. Power Engineering Harbin Institute of Technology Harbin 150001 China

In this paper,some properties of ordered information systems under homomorphism are *** concept of a consistent function with respect to dominance relations is first introduced and its properties are ***,some main invariant properties of dominance relations under relation mappings are *** is proven that attribute reductions in the original ordered information system and its image system are equivalent under the condition of *** means of the results,we can get the smaller image system that has the same reducts as a given massive ordered information system.

关键词： consistent function dominance relation ordered information system homomorphism reduction

Analysis of leakage current in GaAs micro-solar cell arrays

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Science China(Technological Sciences) 2010年第5期53卷 1240-1246页

作者： WANG YanShuo1,CHEN NuoFu1,2,3.zhang XingWang1,BAI YiMing1,WANG Yu1,HUANG TianMao1,zhang Han1 & SHI HuiWei1 1 Key Laboratory of Semiconductor Materials Science,Institute of Semiconductors,Chinese Academy of Sciences,PO Box 912,beijing 100083.China 2 School of Renewable Energy {3.,north China electric power university,beijing 102206,China 3.National Laboratory of Micro-Gravity,Institute of Mechanics,Chinese Academy of Sciences,beijing 100080,China 1. Key Laboratory of Semiconductor Materials Science Institute of Semiconductors Chinese Academy of Sciences PO Box 912 Beijing 100083 China2. School of Renewable Energy Engineering North China Electric Power University Beijing 102206 China3. National Laboratory of Micro-Gravity Institute of Mechanics Chinese Academy of Sciences Beijing 100080 China

The output characteristics of micro-solar cell arrays are analyzed on the basis of a modified model in which the shunt resistance between cell lines results in current *** modification mainly consists of adding a shunt resistor network to the traditional *** obtained results agree well with the reported experimental *** calculation results demonstrate that leakage current in substrate affects seriously the performance of GaAs micro-solar cell *** performance of arrays can be improved by reducing the number of cells per *** addition,at a certain level of integration,an appropriate space occupancy rate of the single cell is recommended for ensuring high open circuit voltages,and it is more appropriate to set the rates at 80%-90% through the calculation.

关键词： micro-solar cell MEMS(micro-electromechanical systems) leakage current

An ecological hydraulic radius approach to estimate the instream ecological water requirement

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Progress in Natural Science:Materials International 2007年第3期17卷 320-327页

作者： LIU Changming and MEN Baohui ( Key Laboratory of Water Cycle and Related Land Surface Process, Institute of Geographical Sciences and Natural Resources Research, Chinese Academy of Sciences, beijing 100101, China Key Laboratory of Water and Sediment Sciences, Ministry of Education & Water Sciences College, beijing Normal university, beijing 100875, China department of Hydraulic and Hydropower engineering, north China electric power university, beijing 102206, China) [a]Key Laboratory of Water Cycle and Related Land Surface Process Institute of Geographical Sciences and Natural Resources Research Chinese Academy of Sciences Beijing China [b]Key Laboratory of Water and Sediment Sciences Ministry of Education & Water Sciences Gllege Beijing Noirnal University Beijing China [c]Departhent of Hydraulic and Hydropower engineering North China Elecfric Power University Beijing China

This essay defines the concepts of ecological flow velocity as well as ecological hydraulic radius (EHR) and proposes an ecological hydraulic radius approach (EHRA) which considers both the watercourse information (including hydraulic radius, roughness coefficient and hydraulic gradient) and the required stream velocity necessary for maintenance of certain ecological functions all together. The key parameter of EHRA is to fix the watercourse cross-sectional flow area corresponding to EHR, by which the relation between parabola shaped cross-sectional flow area and hydraulic radius is deduced. The EHRA not only meets the requirement of flow velocity for adequate fish spawning migration, but also is applicable to the ecological flows in regard with other ecological issues (such as the calculation of the instream flow requirements for transporting sediment and for pollution self-purification, etc.). This essay has illuminated the computational process taking the estimation of ecological water requirement of Zhuba Hydrologyical Station watercourse in Niqu branch of the Yalong River as an example. Additionally, we compare EHRA with Tennant approach. The result shows that the Zhuba Hydrological Station ecological water requirement calculated by EHRA lies between the minimum and favorable ecological water requirement calculated by the Tennant approach. This is due to the fact that the ecological flow velocity (such as the fish spawning migration flow velocity) was taken into consideration, producing results applicable to the practical situation.

关键词： ecological flow flow velocity cross-sectional flow area ecological hydraulic radius (HER) instreamecological water requirement.

Constructing super Gabor frames:the rational time-frequency lattice case

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Science China Mathematics 2010年第12期53卷 3179-3186页

作者： LI ZhongYan 1 & HAN DeGuang 2, 1 department of Mathematics and Physics, north China electric {3. university, beijing 102206, China 2 department of Mathematics, university of Central Florida, Orlando, FL 3.816, USA 1. department of Mathematics and Physics North China Electric Power University Beijing 102206 China2. Department of Mathematics University of Central Florida Orlando FL 32816 USA

For a time-frequency lattice Λ = A Z d × B Z d , it is known that an orthonormal super Gabor frame of length L exists with respect to this lattice if and only if |det( AB) | = 1 L . The proof of this result involves various techniques from multi-lattice tiling and operator algebra theory, and it is far from constructive. In this paper we present a very general scheme for constructing super Gabor frames for the rational lattice case. Our method is based on partitioning an arbitrary fundamental domain of the lattice in the frequency domain such that each subset in the partition tiles R d by the lattice in the time domain. This approach not only provides us a simple algorithm of constructing various kinds of orthonormal super Gabor frames with flexible length and multiplicity, but also allows us to construct super Gabor (non-Riesz) frames with high order smoothness and regularity. Several examples are also presented.

关键词： super Gabor frame orthonormal super frame full rank lattice tiles

CFD simulation of pressure fluctuation characteristics in the gas-solid fluidized bed:Comparisons with experiments

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Petroleum Science 2011年第2期8卷 211-218页

作者： Wang Qingcheng zhang Kai Gu Hongyan beijing Shenwu Thermal Energy Technology Co. LTD Beijing 102200 China State Key Laboratory of Heavy Oil Processing China University of Petroleum Beijing 102249 China National engineering Lab for Biomass power Generation Equipment North China Electric Power University Beijing 102206 China electrical engineering College Guizhou University Guiyang 550025 China

A simple hydrodynamic model based on two-fluid theory, taking into account the effect of discrete particles on both the gas- and solid-phase momentum equations, was used to numerically investigate the pressure fluctuation characteristics in a gas-solid fluidized bed with the aid of CFX 4.4, a commercial CFD software package, by adding user-defined Fortran subroutines. Numerical simulations together with typical experimental measurements show that pressure fluctuations originate above the distributor when a gas pulse is injected into the fluidized bed. The pressure above the bubble gradually increases due to the presence of a rising bubble. When the bubble passes through the bed surface, the pressure near the bed surface gradually decreases to a lower value. Moreover, the pressure signals in the bubbling fluidized beds show obviously periodic characteristics. The major frequency of pressure fluctuations at the same vertical position is affected slightly by the operating gas velocity, and the amplitude of pressure fluctuations is related to both the operating gas velocity and the vertical height. In this study, the influence of the operating gas velocity on the pressure wave propagation velocity can be ignored, and only two peak frequencies in the power spectrum of the pressure fluctuations are observed which are associated with the bubble formation above the distributor and its eruption at the bed surface.

关键词： Gas-solid fluidized bed CFD simulation experimental measurements propagation ofpressure fluctuations pressure wave velocity pressure fluctuation frequency

Application of polynomial chaos on numerical simulation of stochastic cavity flow

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Science China(Technological Sciences) 2010年第10期53卷 2853-2861页

作者： WANG XiaoDong1,2 & KANG Shun1 1 Key Laboratory of Condition Monitoring and Control for power Plant Equipment, Ministry of Education, School of Energy power and Mechanical engineering, {3. China electric power university, beijing 102206, China 2 department of Mechanical engineering, Vrije Universiteit Brussel, Brussels 1050, Belgium 1. Key Laboratory of Condition Monitoring and Control for power Plant Equipment Ministry of Education School of Energy Power and Mechanical Engineering North China Electric Power University Beijing 102206 China2. Department of Mechanical Engineering Vrije Universiteit Brussel Brussels 1050 Belgium

In present paper,the mathematic background of intrusive polynomial chaos (IPC) method and coupling process with one dimension Euler equation were introduced. The IPC method was implemented for the 2D compressible stochastic Navier-Stokes equations to simulate the non-deterministic behavior of a lid driven cavity flow under the influence of uncertainties. The driven velocity and fluid viscosity were supposed respectively to be the uncertain variable which has Gaussian probability distribution. Based on the validation with benchmark results,discussions were mainly focused on the statistic properties of velocity distribution. The results indicated the effect of IPC method on the simulation of propagation of uncertainty in the flow field. For the simulated results of 2D cavity flow,influence of the driven velocity uncertainty is larger than that of viscosity.

关键词： non-deterministic polynomial chaos numerical simulation lid driven cavity flow