检索结果-南通市图书馆

Simulation of aerodynamic performance affected by vortex generators on blunt trailing-edge airfoils

在线全文

学校读者我要写书评

暂无评论

Science china(Technological sciences) 2010年第1期53卷 1-7页

作者： YANG Ke1,2,ZHANG Lei1,3 & XU JianZhong1,2 1 institute of engineering Thermophysics,chinese academy of sciences,beijing 100190,china 2 Key Laboratory of Wind Energy Utilization,chinese academy of sciences,beijing 100190,china 3 Graduate School of chinese academy of sciences,beijing 100190,china 1. institute of engineering Thermophysics Chinese Academy of Sciences Beijing 100190 China2. Key Laboratory of Wind Energy Utilization Chinese Academy of Sciences Beijing 100190 China3. Graduate School of Chinese Academy of Sciences Beijing 100190 China

An investigation was carried out by numerical simulation on a wind turbine airfoil and a blunt trailing-edge airfoil with and without vortex generators (VGs), and the performance of the airfoils was analyzed. By the simulation of airfoil DU 91-W2-250 it was verified that the numerical method and model were credible. Based on this airfoil, a new one with a blunt trailing edge of 6% chord was blended by symmetrically adding thickness, and its characteristics curves were obtained through computing at key angles of attack. Additionally, the pressure distribution on blended airfoil was analyzed by comparing to the airfoil without blend. The interaction of streamwise vortices induced by VGs with trailing vortex or separation vortex was considered, followed by the uncovery of how VGs can suppress the boundary layer separation.

关键词： vortex generators airfoil blunt trailing-edge

On the contact width in generalized plain strain JKR model for isotropic solids

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica Sinica 2009年第4期25卷 491-497页

作者： Cong Yan Shaohua Chen LNM, institute of Mechanics, chinese academy of sciences,100190 beijing. china LNM Institute of Mechanics Chinese Academy of Sciences 100190 Beijing China

Adhesive contact model between an elastic cylinder and an elastic half space is studied in the present paper, in which an external pulling force is acted on the above cylinder with an arbitrary direction and the contact width is assumed to be asymmetric with respect to the structure. Solutions to the asymmetric model are obtained and the effect of the asymmetric contact width on the whole pulling process is mainly discussed. It is found that the smaller the absolute value of Dundurs＇ parameter 13 or the larger the pulling angle O, the more reasonable the symmetric model would be to approximate the asymmetric one.

关键词： Contact mechanics Generalized JKRmodel Asymmetric contact width Oscillatory solution Non-oscillatory solution

Synthesis,characterization,and thermostability of bis(2,2,6,6-tetramethyl-3,5-heptanedionato)copper(Ⅱ)

在线全文

学校读者我要写书评

暂无评论

Rare Metals 2012年第4期31卷 343-349页

作者： ZHANG Teng,GU Hongwei,DING Fazhu,QU Fei,and DAI Shaotao Key Laboratory of Applied Superconductivity,institute of electrical engineering,chinese academy of sciences,beijing 100190,china Key Laboratory of Applied Superconductivity Institute of Electrical Engineering Chinese Academy of Sciences Beijing China

Owing to the adaptability to large scale processing,excellent composition control and film uniformity,the metal-organic chemical vapor deposition（MOCVD） technique is a promising process for high-temperature superconductor YBa;Cu;O;（YBCO） *** this technique,the evaporation characteristics and thermostability of adopted precursors in whole process will decide the quality and reproducible results of YBCO *** the present report,bis（2,2,6,6-tetramethyl-3,5-heptanedionato）copper（II）(Cu（TMHD）;) was synthesized by the interaction of copper acetate hydrate with TMHD in methanol solution,and its structure was identified by FTIR,1 H NMR,and EI-MS ***,thermal property and the kinetics of decomposition were systematically investigated by nonisothermal thermogravimetric analysis methods（TGA） at different heating rates in streams of N;,and the average apparent activation energy of evaporation process was evaluated by the Ozawa,Kissinger,and Friedman *** possible conversion function was estimated through the Coats-Redfern method to characterize the evaporation patterns and followed a phase boundary reaction mechanism by the contracting area equation with average activation energy of 85.1 kJ·mol;.

关键词： Cu(TMHD)_2 metal-organic chemical vapor deposition(MOCVD) synthesis thermostability

Euler solution using adaptive Cartesian grid with a gridless boundary treatment

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica Sinica 2009年第2期25卷 187-196页

作者： L. Xiang G. Yang LHD of institute of Mechanics, chinese academy of sciences, 100190 beijing, china LHD of institute of Mechanics Chinese Academy of Sciences 100190 Beijing China

A quadtree-based adaptive Cartesian grid generator and flow solver were developed. The grid adaptation based on pressure or density gradient was performed and a gridless method based on the least-square fashion was used to treat the wall surface boundary condition, which is generally difficult to be handled for the common Cartesian grid. First, to validate the technique of grid adaptation, the benchmarks over a forward-facing step and double Mach reflection were computed. Second, the flows over the NACA 0012 airfoil and a two-element airfoil were calculated to validate the developed gridless method. The computational results indi- cate the developed method is reasonable for complex flows.

关键词： Cartesian grid Gridless method Adaptation technique Euler solution

Onset of cavitation by the strong tension spike from a tube-arrest apparatus

在线全文

学校读者我要写书评

暂无评论

Science china(Physics,Mechanics & Astronomy) 2010年第2期53卷 301-305页

作者： YING ChongFu & LI Chao institute of Acoustics,chinese academy of sciences,beijing 100190,china 1. institute of Acoustics Chinese Academy of Sciences Beijing 100190 China

Our earlier paper has identified a wave of Type 1 that is the pressure wave generated in the liquid-filled glass tube through the tube-arrest method by pulling and arresting the tube,when cavitation is prohibited. If cavitation is produced,a wave of Type 2 generally appears. The present paper takes the transition between wave types as indication of cavitation onset,and looks for a liquid parameter which controls the onset. One such an attempt shows the concentration of a dissolved gas in the liquid is the controlling factor with the result that the threshold of cavitation onset decreases with the increase of the concentration. Then a specially designed experiment reveals that possibly the mobility of the gas molecules (and also that of the liquid molecules) transiently affects the threshold so as to induce a large rise and fall in time of hours. The threshold finally settles down to some stable value under atmospheric pressure.

关键词： tube-arrest method cavitation onset controlling parameter concentration of dissolved gas mobile gas molecules liq-uid tensile strength

Research of the Gas-solid Flow Character Based on the DEM Method

在线全文

学校读者我要写书评

暂无评论

Journal of Thermal Science 2011年第6期20卷 521-526页

作者： Xueyao Wang and Yunhan Xiao Research Center for Clean Energy and Power,chinese academy of sciences Key Laboratory of Advanced Energy and Power,chinese academy of sciences (institute of engineering Thermophysics),beijing,100190,china Research Center for Clean Energy and Power Chinese Academy of Sciences Beijing China Key Laboratory of Advanced Energy and Power Chinese Academy of Sciences (Institute of Engineering Thermophysics) Beijing China

Numerical simulation of gas-solid flow behaviors in a rectangular fluidized bed is carried out three dimensionally by the discrete element method (DEM).Euler method and Lagrange method are employed to deal with the gas phase and solid phase *** collided force among particles,striking force between particle and wall,drag force,gravity,Magnus lift force and Saffman lift force are considered when establishing the mathematic ***-sphere model is used to describe the collision of *** addition,the Euler method is also used for modeling the solid phase to compare with the results of *** flow patterns,particle mean velocities,particles' diffusion and pressure drop of the bed under typical operating conditions are *** results show that the DEM method can describe the detailed information among particles,while the Euler-Euler method cannot capture the micro-scale *** matter which method is used,the diffusion of particles increases with the increase of gas *** the gathering and crushing of particles cannot be simulated,so the energy loss of particles' collision cannot be calculated and the diffusion by using the Euler-Euler method is *** addition,it is shown by DEM method,with strengthening of the carrying capacity,more and more particles can be schlepped upward and the dense suspension upflow pattern can be ***,the results given by the Euler-Euler method are not consistent with the real situation.

关键词： DEM gas-solid flow numerical simulation

Challenges and innovations in green process intensification

在线全文

学校读者我要写书评

暂无评论

Science china Chemistry 2010年第7期53卷 1470-1475页

作者： LIU HuiZhou,LIANG XiangFeng,YANG LiangRong & CHEN JiaYong institute of Process engineering,chinese academy of sciences,beijing 100190,china 1. institute of Process engineering Chinese Academy of Sciences Beijing 100190 China

Process intensification is one of the most significant trends in current chemical engineering and process *** recent years,the desire to become more "green" in processing has always been tied to the requirement of being *** review discusses the challenges of process engineering and summarizes the key role of fundamentals for green process intensification.

关键词： green chemistry process intensification

Interface delamination of the thermal barrier coating subjected to local heating

在线全文

学校读者我要写书评

暂无评论

Science china(Technological sciences) 2010年第12期53卷 3168-3174页

作者： WU ChenWu, HUANG ChenGuang & CHEN GuangNan institute of Mechanics, chinese academy of sciences, beijing 100190, china 1. institute of Mechanics Chinese Academy of Sciences Beijing 100190 China

To investigate the possible failure modes of the thermal barrier coating (TBC) used to protect the scramjet combustion chamber, the local heating via laser beam irradiation was utilized to simulate the service condition of high thermal flux and high temperature gradient. Firstly, the experimental method and process were described and the typical fracture morphology of the TBC under test were provided. Then, the theoretical and finite element modeling were carried out to study the temperature, deformation and stresses of the specimen when the top ceramic coat was subjected to local heating, and to demonstrate the mechanism on the failure of the TBC. It is revealed that the interface delamination shall appear and ultimately lead to the failure of the TBC under such thermal loading of local quick heating. According to the outcome of this study, the driving force of the interface delamination is influenced greatly by the key structural parameters and performance matching. Moreover, by utilizing the rules of the effects of these parameters on the fracture driving force, there is some possibility for the designer to optimize the performances of the TBC.

关键词： TBC local heating interface delamination FE modeling

Anti-saturation block adaptive quantization algorithm for SAR raw data compression over the whole set of saturation degrees

在线全文

学校读者我要写书评

暂无评论

Progress in Natural Science:Materials International 2009年第8期19卷 1003-1009页

作者： Haiming Qi , Weidong Yu institute of Electronics, chinese academy of sciences, beijing 100190, china [a]institute of Electronics Chinese Academy of Sciences Beijing 100190 China

In order to improve the performance of block adaptive quantization (BAQ) when the output of the analog to digital converter (ADC) is saturated, this paper proposes an anti-saturation BAQ algorithm. First, the concept of the standard deviation of the output signal (SDOS) of the ADC is proposed. Also, unlike traditional normalization processing, SDOS is used and the mapping between SDOS and the average signal magnitude is deduced. Second, the saturation term is introduced to the Lloyd–Max quantizer and an optimal non-uniform scalar quantizer for saturated SAR raw data quantization is proposed. After this, the implementation scheme for the proposed algorithm using an FPGA is analyzed in detail. Third, the relationships among the saturation degree of the signal, the peak-topeak value of the ADC, standard deviation of the input and output signal of the ADC and the average signal magnitude are deduced. Based on these relationships, a power compensation decoder is designed for encoding. Numerical experiment results based on ERS-1 and the simulated data show that the performance of the proposed algorithm is better than that of BAQ.

关键词： Synthetic aperture radar (SAR) Raw data compression Block adaptive quantization (BAQ) Anti-saturation