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Precise drag prediction of airfoil flows by a new algebraic model

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Acta Mechanica Sinica 2020年第1期36卷 35-43页

作者： Meng-Juan xiao Zhen-Su she State Key Laboratory for Turbulence and Complex Systems College of EngineeringPeking UniversityBeijing100871China

We report the results of accurate prediction of lift(C L)and drag(C d)coefficients of two typical airfoil flows(NACA0012 and RAE2822)by a new algebraic turbulence model,in which the eddy viscosity is specified by a stress length(SL)function predicted by structural ensemble dynamics(SEd)*** accuracy of the prediction of C d with error of a few counts(one count is 10−4)and of C L with error under 1%-2%are uniformly obtained for varying angles of attack(AoA),indicating an order of magnitude improvement of drag prediction accuracy compared to currently used models(typically around 20 to 30 counts).More interestingly,the SEd-SL model is distinguished with fewer parameters of clear physical meaning,which quantify underlying turbulent boundary layer(TBL)with a universal multi-layer structure,and is thus promising to be more easily generalizable to complex *** use of the new model for the calibration of flow condition in experiment and the extraction of flow physics from numerical simulation data of aeronautic flows are discussed.

关键词： Lift and drag coefficients Airfoil Flows Stress Length Structural ensemble dynamics

Fabrication and Life Prediction of SSiC Ceramic Joint Joined with Silicon Resin YR3370

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Chinese Journal of Aeronautics 2007年第1期20卷 81-85页

作者： YUAN xiao-kun xU Bing-she School of Materials Science and Engineering Beijing University of Aeronautics and Astronautics Beijing 100083 China College of Materials Science and Engineering Taiyuan University of Technology Taiyuan 030024 China

Joints between sintered silicon carbide （SSiC） were produced using a polysiloxane silicon resin YR3370 （gE Toshiba Silicones） as joining material. Samples were heat treated in a 99.99% nitrogen flux at temperatures ranging from 1 100 ℃ to 1 300 ℃. Three point bending strength of the joint reached the maximum of 179 MPa as joined at 1 200℃. The joining layer is continuous, homogeneous and densified and has a thickness of 2 μm -5μm. The joining mechanism is that the amorphous silicon oxycarbide （SixOyCz） ceramic pyrolyzed from silicon resin YR3370 acts as an inorganic adhesive to SSiC substrate, which means the formation of the continuous Si-C bond structure between SixOyCz structure and SSiC substrate. Life prediction of the ceramic joint can be realized through the measurement of the critical time of the joint after the cyclic loading test.

关键词： silicon resin YR3370 SiC ceramic ceramic joining joint life

A Modulus Variation Model of Concrete under External Sulfate Attack:New Perspective from Statistical Evolution of Microcracks

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Journal of Wuhan University of Technology(Materials Science) 2018年第6期33卷 1465-1471页

作者： ZHANg Hao she Wei School of Material Science and Engineering Southeast UniversityNanjing 211189China State Key Laboratory of High Performance Civil Engineering Material Nanjing 211100China

A numerical model was proposed to describe the modulus variation of mortar exposed to external sulfate attack and the effectivity was verified by experiments. The model joints statistical evolution of microcracks to effective elastic modulus with microcracks and is applied to predict the damage degree of mortar attacked by sulfate. The experimental results show that the model can predict the modulus variation development of the specimen and the microcraks density. The elastic modulus values calculated by the model are consistent with that measured by experiments. The model focuses on nucleation of microcracks and finds that the theoretical results of microcracks number density show a linear growth over time in mortar. Compared with other sulfate attack damage model, this model provides a more suitable damage evolution equation that can be used to analyze the chemically assisted damage.

关键词： sulfate attack effective elastic modulus microcracks number density damage evolution

A moment-based stochastic edge-based smoothed finite element method for electromagnetic forming process

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Science China(Technological Sciences) 2020年第9期63卷 1739-1750页

作者： YANg Qin WANg Bing LI she CUI xiangYang State Key Laboratory of Advanced design and Maufacturing for Vehicle Body Hunan UniversityChangsha 410082China

In this paper, a novel stochastic method named as the moment-based stochastic edge-based finite element method(MSES-FEM)is proposed to deal with the uncertain electromagnetic problems. First, electromagnetic and mechanical field are formulated by smoothed galerkin Weak Form under edge-based smoothed finite element method(ES-FEM) scheme. The moment analysis is then applied to obtain the first four moments of the responses and to observe the effects of each random variable on electromagnetic field responses. The maximum entropy theory is employed to calculate the probability density functions(PdFs) of the responses. A quasi-static electromagnetic problem and a practical electromagnetic forming problem(EMF) are performed. The proposed method successfully solves stochastic electromagnetic forming analysis under the uncertain parameters. Numerical results obtained by the proposed MSES-FEM are quite satisfactory with the ones by the Monte Carlo simulation(MCS).

关键词： MSES-FEM electromagnetic forming problem the moment analysis the maximum entropy theory probability density function

The application of C–H bond functionalization in the total syntheses of indole natural products

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Organic Chemistry Frontiers 2022年第4期9卷 1195-1210页

作者： dong-xing Tan Fu-she Han CAS Key Lab of High-Performance Synthetic Rubber and its Composite Materials Changchun Institute of Applied ChemistryChinese Academy of Sciences5625 Renmin StreetChangchunJilin 130022China

The direct functionalization of unactivated C–H bonds has been a rapidly growing field in organic chem-istry in recent years because of its indisputable advantages in bond forming reactions in terms of step and atom-... 详细信息

关键词： functionalization bonds bond

Effects of the width and thickness of slabs on broadening in continuous casting

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International Journal of Minerals,Metallurgy and Materials 2010年第6期17卷 723-728页

作者： Jian-xun Fu Jing-she Li Hui Zhang School of Metallurgical and Ecological Engineering University of Science and Technology Beijing Beijing 100083 China National Engineering Research Center of Continuous Casting Technology Central Iron and Steel Research Institute Beijing 100081 China

A 3d viscoelastic-plastic thermal-mechanical coupled finite element model was built on the basis of the secondary development of the commercial software ***. Numerical simulations were performed to study slab broadening in the secondary cooling zone. The effects of slab width and thickness on slab broadening were considered. The obtained results reveal that the width broadening is noticeable, and the ratio of ultimate broadening slightly increases with the increase of slab width. This agrees well with the measured data in practice. There is no obvious increase in ultimate broadening when the thickness of slabs increases.

关键词： continuous casting slabs broadening finite element method

Three dimensional K-Tz stress fields around the embedded center elliptical crack front in elastic plates

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Acta Mechanica Sinica 2006年第2期22卷 148-155页

作者： Junhua Zhao Wanlin guo Chongmin she Bo Meng eng Institute of Nano Science Nanjing University of Aeronautics Astronautics Nanjing 210016 China

Through detailed three-dimensional （3d） finite element （FE） calculations, the out-of-plane constraints Tz along embedded center-elliptical cracks in mode I elastic plates are studied. The distributions of Tz are obtained near the crack front with aspect ratios （a/c） of 0.2, 0.4, 0.5, 0.6, 0.8 and 1.0. Tz decreases from an approximate value of Poisson ratio v at the crack tip to zero with increasing normalized radial distances （r/a） in the normal plane of the crack front line, and increases gradually when the elliptical parameter angle φ changes from 0° to 90°at the same r/a. With a/c rising to 1.0, Tz is getting nearly independent of φ and is only related to r/a. Based on the present FE calculations for Tz, empirical formulas for Tz are obtained to describe the 3d distribution of Tz for embedded center-elliptical cracks using the least squares method in the range of 0.2 ≤ a/c ≤ 1.0. These Tz results together with the corresponding stress intensity factor K are well suitable for the analysis of the 3d embedded centerelliptical crack from field, and a two-parameter K-Tz principle is proposed.

关键词： Three-dimensional finite element Out-of-plane constraint Tz Embedded elliptical crack Stress intensity factor T-Stress Stress field

Estimation and compensation of periodic disturbance using internal-model-based equivalent-input-disturbance approach

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Science China(Information Sciences) 2022年第8期65卷 150-163页

作者： Qicheng MEI Jinhua she Zhentao LIU Min WU School of Automation China University of Geosciences Hubei Key Laboratory of Advanced Control and Intelligent Automation for Complex Systems School of Engineering Tokyo University of Technology

This paper presents an improved equivalent-input-disturbance(EId) approach to deal with periodic disturbances. The approach has two degrees of freedom. One is an improved EId compensator, in which a repetitive controller is inserted in this study. The other is a conventional servo system for a reference *** improved EId compensator estimates and compensates for periodic disturbances without steady-state error, and the servo system ensures a satisfactory tracking performance. The improved EId compensator is designed using the linear-matrix-inequality(LMI) method. Three parameters in an LMI are selected using the particle-swarm-optimization(PSO) algorithm. The state-feedback gain of the conventional servo system is designed using the linear-quadratic-regulator(LQR) method. Simulation results of a rotational control system demonstrate the validity of the approach and its advantage over others.

关键词： equivalent input disturbance (EId) linear matrix inequality (LMI) linear quadratic regulator (LQR) particle swarm optimization (PSO) periodic disturbance repetitive control

design of a discrete-time Output-feedback Based Repetitive-control System

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International Journal of Automation and computing 2013年第4期10卷 343-349页

作者： Lan Zhou Jin-Hua she Min Wu School of Information and Electrical Engineering Hunan University of Science and Technology School of Computer Science Tokyo University of Technology School of Information Science and Engineering Central South University

This paper deals with the problem of designing a robust discrete output-feedback based repetitive-control system for a class of linear plants with periodic uncertainties. The periodicity of the repetitive-control system is exploited to establish a two-dimensional （2d） model that converts the design problem into a robust stabilization problem for a discrete 2d system. By employing Lyapunov stability theory and the singular-value decomposition of the output matrix, a linear-matrix-inequality （LMI） based stability condition is derived. The condition can be used directly to design the gains of the repetitive controller. Two tuning parameters in the LMI enable the preferential adjustment of control and learning. A numerical example illustrates the design procedure and demonstrates the validity of the method.

关键词： Repetitive control discrete two-dimensional system singular-value decomposition output feedback linear matrix in- equality (LMI).