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Application and Comparison of Two SGS Models in Large Eddy Simulation of FreeTurbulent Jet Flow

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Communications in Nonlinear science and Numerical Simulation 1999年第1期4卷 12-19页

作者： Hong YAN and Mingde SU (Department of Engineering Mechanics, tsinghua university, beijing 100084, china) Department of Engineering Mechanics Tsinghua University Beijing 100084 China

Large eddy simulations of spatially evolved turbulent round jets were presented. The two SGS models called the standard Smagorinsky’s eddy viscosity model and the non-eddy viscosity stimulated small scale(SSS) model developed by Shah & Ferziger were applied. The Reynolds number of the flow was taken as 10000 based on the orifice diameter and the axial velocity in the orifice. The comparison between these two models showed that the standard Smagorinsky’s viscosity model with Smagorinsky’s constant of 0.1 underestimated the turbulent intensity, while the SSS model showed a better agreement with the experiment. Also the SSS model was used to investigate the development of vortex. The convective boundary condition at the outflow boundary was adopted to ensure less effect of noise on the upstream.

关键词： stimulated small scale model smagorinsky’s eddy viscosity model Round jet, Large eddy simulation

ENTROPY,information,NOISE-STUDIES ON SYSTEM EVOLUTION

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Systems science and Systems Engineering 2003年第1期12卷 2-12页

作者： Weimin ZHENGSchool of Economics and Management tsinghua university. beijing 100084, china School of Economics and Management Tsinghua University

Universe, ecosystem, social system, etc. are evolving systems. The evolving processes of these systems have gradual small changes and rapid drastic changes with uncertainties under the constraints of environment. Systems, as a whole, are evolving toward complexity, diversity and variety with fluctuations and jumps. New order emerges from 'mutations'. The evolution is both chance-dependent and path-dependent. In this paper three basics: entropy, information and noise are emphasized with regard to system evolution which is a field that can give people wisdom to solve system problems with domain knowledge.

关键词： Entropy information noise

Orthogonal linear polarized lasers (Ⅲ)——Applications in self-sensing

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Progress in Natural science:Materials International 2005年第11期15卷 961-971页

作者： ZHANG Shulian, DU Wenhua and LIU Gang (The State Key laboratory of Precision Measurement technology and Instruments, Department of Precision Instruments, tsinghua university, {3., china) The State Key laboratory of Precision Measurement technology and Instruments Department of Precision Instruments Tsinghua University Beijing 100084 China

In this paper, the applications of orthogonal linear polarized lasers in self-sensing are reviewed. The properties for such a laser include the production of a new frequency in one longitudinal mode spacing, the tuning of frequency difference, the change of polarization states as cavity tuning, the control of mode competition intensity, the optical feedback, and so on. The orthogonal polarized lasers have been used as a laser nanometer ruler based on competition between two polarized lights in a HeNe laser and as a displacement measurement tool based on the optical feedback in the orthogonal polarized lasers. They are also used in the phase retardation measurement of a waveplate, the angle measurement, the vibration measurement, the pressure/force measurement, the weak magnetic field measurement, and so on. The structures of these new devices are simple and compact with the great advantages of high resolution and high accuracy. Some of these devices can trace to the source of the laser wavelength. The nanometer laser ruler is an example whose measurement range is 12 mm, resolution is 79 nm and linearity is less than 5×10-5. The repeatability of the phase retardation measuring system of waveplate can reach 3..

关键词： orthogonal polarized laser frequency splitting optical feedback vibration measurement displacement measurement waveplate measurement angle measurement.

Effect of Carbon on Dynamic Recrystallization Behavior of Vanadium Microalloy Steels

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Journal of Iron and Steel Research International 2011年第S1期18卷 129-134页

作者： LIU Guo-quan 1,2,ZHAO Hai-tao 1,WU Jin-bin 1,WANG Cheng-yang 1,XU Lei 1,3.(1.School of Materials science and Engineering,university of science and {3. beijing,beijing 100083.china 2.State Key laboratory for Advanced Metals and Materials,university of science and {3. beijing,beijing 100083.china 3.Department of Materials science and Engineering,tsinghua university,beijing 100084,china) Univ Sci & Technol beijing Sch Mat Sci & Engn Beijing 100083 Peoples R China Univ Sci & Technol beijing State Key Lab Adv Met & Mat Beijing 100083 Peoples R China tsinghua Univ Dept Mat Sci & Engn Beijing 100084 Peoples R China

The hot working behavior especially dynamic recrystallization of low-carbon and medium-carbon vanadium microalloy steels has been studied by performing isothermally compression tests and Avrami *** Avrami plots of the two experiment steels have been constructed based on flow stress curves following a new approach (Jonas,et *** Mater.,2009,57(2):2748-2756;Wu et al,Acta ***.,2010,46(7):83.-843..It is experimentally found that the carbon effect on dynamic recrystallization is opposite to each other in lower and higher strain ranges:Carbon causes a softening effect at low strain rates (0.01,0.1,and 1.0 s-1),and a hardening effect at high strain rates (10.0 and 3..0 s-1).Correspondingly,carbon promotes the dynamic recrystallization at low strain rates and retards the dynamic recrystallization at high strain rates in the experimental *** phenomenon is then tentatively explained based on the possible mechanisms of dynamic process at different strain rates.

关键词： vanadium microalloy steels hot working dynamic recrystallization carbon strain rate Avrami modeling

Cloning and characterization of cotton heteromeric acetyl-CoA carboxylase genes

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Progress in Natural science:Materials International 2007年第12期17卷 1412-1418页

作者： Qiao Zhixin and Liu Jinyuan(laboratory of Molecular Biology and Protein science laboratory of the Ministry of Education, Department of Biological sciences and Biotechnology, tsinghua university, beijing 100084, china) laboratory of Molecular Biology and Protein science laboratory of the Ministry of Education Department of Biological Sciences and Biotechnology Tsinghua University Beijing 100084 China

Heteromeric acetyl-coenzyme A (CoA) carboxylase (ACCase) catalyzes the formation of malonyl-CoA from acetyl-CoA. It plays an essential role in fatty acid synthesis in prokaryotes and most of plants. The heteromeric ACCase is composed of four subunits: biotin carboxylase (BC), biotin carboxyl carrier protein (BCCP), and α- and β-subunits of carboxyltransferase (α- and β-CT). In this study, we cloned five novel genes encoding the subunits of heteromeric ACCase (one BC, BCCP and β-CT, and two α-CTs) from cotton (Gossypium hirsutum cv. zhongmian 3.) by RACE-PCR. The deduced amino acid sequence of these cDNAs shares high similarity with other reported heteromeric ACCase subunits. The phylogenetic analysis indicated that the different subunits of heteromeric ACCase were grouped in a similar pattern. Southern blot analysis revealed the milti-copy patterns of these heteromeric ACCase genes in cotton genome. Semi-quantitative RT-PCR demonstrated that heteromeric ACCase genes were constitutively expressed in all of the cotton tissues, but the transcripts accumulated at a relatively low level in roots. To our knowledge, this is the first report about characterization of the heteromeric ACCase genes in cotton.

关键词： heteromeric ACCase cotton gene cloning fatty acid synthesis.

Sediment transport capacity of hyperconcentrated flow

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science china(Physics,Mechanics & Astronomy) 2008年第8期51卷 961-975页

作者： SHU AnPing1,2 & FEI XiangJun2 1 School of Environment & Key laboratory of Water and Sediment sciences,Ministry of Education,beijing Normal {3.,beijing 100875,china 2 State Key laboratory of Hydroscience and Engineering,tsinghua university,beijing 100084,china School of Environment & Key laboratory of Water and Sediment sciences Ministry of Education Beijing Normal University Beijing 100875 China State Key laboratory of Hydroscience and Engineering Tsinghua University Beijing 100084 China

As one of the most important components of river mechanics,sediment transport capacity of sediment-laden flows has attracted much attention from many researchers working on river mechanics and hydraulic engineering. Based on the time-averaged equation for a turbulent energy equilibrium in solid and liquid two-phase flow,an expression for the efficiency coefficient of suspended load movement was derived for the two-dimensional,steady,uniform,fully-developed turbulent flow. A new structural expression of sediment transport capacity was achieved. Using 115 runs of flume experimental data,which were obtained through two kinds of sediment transport experiments in the state of equilibrium,in combination with the basic rheological and sediment transporting characteristics of hyperconcentrated flow,the main parameters in the structural expression of sediment transport capacity were calibrated,and a new formula of sediment transport capacity for hyperconcentrated flow was developed. A large amount of field data from the Yellow River,Wuding River,and Yangtze River,etc. were adopted to verify the new formula and good agreement was obtained. These results above contribute to an improved theoretical system of river mechanics and a reliable tool for management of rivers carrying high concentration of sediments.

关键词： hyperconcentrated flow turbulent energy equilibrium efficiency coefficient sediment transport capacity

Research and development on transonic compressor of high pressure ratio turbocharger for vehicle internal combustion engines

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science china(Technological sciences) 2010年第7期53卷 1817-1823页

作者： ZHENG XinQian, ZHANG YangJun & YANG MingYang State Key laboratory of Automotive Safety and Energy, tsinghua university, beijing 100084, {3. 1. State Key laboratory of Automotive Safety and Energy Tsinghua University Beijing 100084 China

The pressure ratio required for a turbocharger centrifugal compressor increases with internal combustion engine power density. High pressure ratio causes a transonic flow field at the impeller inducer. Transonic flow narrows the stable flow range and de-teriorates stage efficiency. In this work, an advanced high pressure ratio transonic compressor was designed. The experimental results show that the maximum pressure ratio of this turbocharger is about 4.2, the maximum efficiency is above 80% and the stable flow range at the designed rotating speed is up to 3.%. A turbocharger with this transonic compressor has been applied to some vehicle research actually, and improved power density by 40%.

关键词： turbocharger internal combustion (IC) engine compressor high pressure ratio transonic

Simulation of dam breach development for emergency treatment of the Tangjiashan Quake Lake in china

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science china(Technological sciences) 2008年第S2期51卷 82-94页

作者： WANG GuangQian,LIU Fan,FU XuDong & LI TieJian State Key laboratory of Hydroscience and Engineering,tsinghua university,{3.,china State Key laboratory of Hydroscience and Engineering Tsinghua University Beijing 100084 China

The Tangjiashan Quake Lake is the largest quake lake triggered by the 5.12 Wenchuan Earthquake that happened on May 12,2008 in china,posing high risk of catastrophic flash flood hazards to downstream human life and properties.A physics-based numerical simulation approach is proposed for real-time prediction of dam breach development of the Tangjiashan Quake Lake in the case of emergency *** erosion and lateral development of the dam breach are represented through accounting for the underlying physics including selective sediment transport and gravitational *** breach erosion model that involves few parameters enables quick calibration based on the monitored hydrological data in emergency analysis where fully geotechnical information about the barrier dam is not *** process of dam breach development is found to be nonlinear in cascades due to the combined effects of headcutting and bank *** agreement between the simulation results and the observed data shows the applicability of the present approach for emergency analysis of quake *** will arise in the situation where the soil composition of barrier dam is significantly *** of circular arc failure for cohesive soil and lateral seepage in bank slope will also enhance its applicability to complex situations.

关键词： quake lake earthquake dam breach simulation numerical model erosion collapse headcutting

Gas kinetic algorithm for flows in Poiseuille-like microchannels using Boltzmann model equation

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science china(Physics,Mechanics & Astronomy) 2005年第4期48卷 496-512页

作者： LI Zhihui1,2, ZHANG Hanxin1 & FU Song2 ⒈ National laboratory for CFD, Hypervelocity Aerodynamics Institute,china Aerodynamics Research and Development Center,Mianyang 621000,china 2.Department of Engineering Mechanics,{3.,beijing 100084,china 1. National laboratory for CFD Hypervelocity Aerodynamics Institute China Aerodynamics Research and Development Center 621000 Mianyang China 2. Department of Engineering Mechanics Tsinghua University 100084 Beijing China

The gas-kinetic unified algorithm using Boltzmann model equation have been extended and developed to solve the micro-scale gas flows in Poiseuille-like micro-channels from Micro-Electro-Mechanical Systems (MEMS). The numerical modeling of the gas kinetic boundary conditions suitable for micro-scale gas flows is presented. To test the present method, the classical Couette flows with various Knudsen numbers, the gas flows from short microchannels like plane Poiseuille and the pressure-driven gas flows in two-dimensional short microchannels have been simulated and compared with the approximate solutions of the Boltzmann equation, the related DSMC results, the modified N-S solutions with slip-flow boundary theory, the gas-kinetic BGK-Burnett solutions and the experimental data. The comparisons show that the present gas-kinetic numerical algorithm using the mesoscopic Boltzmann simplified velocity distribution function equation can effectively simulate and reveal the gas flows in microchannels. The numerical experience indicates that this method may be a powerful tool in the numerical simulation of micro-scale gas flows from MEMS.

关键词： Boltzmann model equation, discrete velocity ordinate method, finite-difference scheme, Couette flow, Poiseuille flow, gas flow in short-microchannel.