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Large-eddy simulations and vortex structures of turbulent jets in crossflow

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science china(Physics,Mechanics & Astronomy) 2007年第1期50卷 118-132页

作者： GUAN Hui1,2 & WU ChuiJie2 1 school of mechanical and power engineering,east china university of science and technology,shanghai 200237,china 2 Research Center for Fluid Dynamics,PLA university of science and technology,Nanjing 211101,china school of mechanical and power engineering East China University of Science and Technology Shanghai China Research Center for Fluid Dynamics PLA University of Science and Technology Nanjing China

Using the method of large-eddy simulation, the 3-dimensional turbulent jets in crossflow with stream-wise and transverse arrangements of nozzle are simulated, emphasizing on the dynamical process of generation and evolution of vortex structures in these flows. The results show that the basic vortex structures in literatures, such as the counter-rotating vortex pair, leading-edge vortices, lee-side vortices, hanging vortices, kidney vortices and anti-kidney vortices, are not independent physical substances, but local structures of the basic vortex structure of turbulent jets in crossflow-the 3-D stretching vortex rings originating from the orifice of the nozzle, which is discovered in this study. Therefore, the most important large-scale structures of turbulent jets in crossflow are unified to the 3-D vortex rings which stretch and twist in stream-wise and swing in transverse directions. We also found that the shedding frequencies of vortex rings are much lower than the one corresponding to the appearance of leading-edge and lee-side vortices in the turbulent jets.

关键词： turbulent jet in crossflow coherent structure large-eddy simulation

Flow Behavior and Evolution of Microstructure during Hot Deformation for a High Mo Stainless Steel

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Journal of Materials science & technology 2000年第3期16卷 341-344页

作者： Yourong xu, Liangsheng CHEN, Deying wang and Lei JIN (school of Materials science and engineering, shanghai university, shanghai 201800, china) school of Materials science and engineering Shanghai University Shanghai 201800 China

The mechanical behaviors of high Mo austenitic stainless steel OOCr20Nil8Mo6Cu[N] have been investigated using the methods of hot compression simulation test on the Thermecmaster-Z simulator. The dynamic recrystallization kinetic equation was established, Avrami coefficient n lies in between 0.9～2 depending on deformation parameters. A perfect flow stress model considering dynamic recrystallization was also established. Dynamic recrystallization tends to complete at 1050℃ and high strain rate, but at temperature below 950℃, it is hard to occur. Double-stage interrupt compression tests were carried out. Activation energy for static and metadynamic re-crystallization have been obtained respectively (QSRX=483.7, QMDEX=253.5 kJ/mol). Avrami coefficient of MDRX is about 0.5, and t.0.5-kinetics equations of SRX and MDRX have also been constructed. The evolution of microstructures during interrupt compression deformation was investigated. Static and metadynamic recrystaltlzation is essential to improve plasticity, at temperature above 1000℃ increasing interpass time has advantage for static and metadynamic recrystallization.

关键词： Stainless steel

Bifurcation of Periodic Motion of Rigid Rotor System Supported by Angular Contact Ball Bearings

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Transactions of Tianjin university 2011年第6期17卷 404-410页

作者：崔立刘长利郑建荣 Key Laboratory of Safety science of Pressurized System of Ministry of Education School of Mechanical and Power EngineeringEast China University of Science and Technology

Rotor systems supported by angular contact ball bearings are complicated due to nonlinear Hertzian contact force. In this paper, nonlinear bearing forces of ball bearing under five-dimensional loads are given, and 5-DOF dynamic equations of a rigid rotor ball bearing system are established. Continuation-shooting algorithm for periodic solutions of the nonlinear non-autonomous dynamic system and Floquet multipliers of the system are used. Furthermore, the bifurcation and stability of the periodic motion of the system in different parametric domains are also studied. Results show that the bifurcation and stability of period-1 motion vary with structural parameters and operating parameters of the rigid rotor ball bearing system. Avoidance of unbalanced force and bending moment, appropriate initial contact angle, axial load and damping factor help enhance the unstable rotating speed of period-1 motion.

关键词： angular contact ball bearing rigid rotor system bifurcation periodic motion continuation-shooting algorithm

Chimney Effect Assessment of the Double-skin Facade

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湖南大学学报（自然科学版） 2009年第S1期36卷 146-150页

作者： QIU Zhong-zhu1,LI Peng2,CHOW Tin-tai3,REN Jian-xing1,wang Wen-huan1(1.school of Energy & Environment engineering,shanghai university of Electric power,shanghai 20090,china 2.school of mechanical engineering,Tongji university,shanghai 200092,china 3.Division of Building science & technology,City university of Hong Kong,Hong Kong SAR,china) school of Energy and Environment engineering Shanghai University of Electric Power Shanghai 200090 China school of mechanical engineering Tongji University Shanghai 200092 China Division of Building science and technology City University of Hong Kong Hong Kong Hong Kong

The mathematic model of heat transfer through ventilated double glazing was verified with the measured data,which were from a test chamber equipped with glass face temperature,solar radiation,ambient temperature,and wind speed measurement *** the model validation,the double-skin facade assessment was carried out through simulation with ESP-r software integrating thermal simulation and air low net work *** air flow situation in the air gap was analyzed on the basis of the hourly air velocity simulation data within typical winter week,summer week,spring week and autumn *** differences of chimney effect in different seasons were discussed,and the thermal loads resulted from the ventilated and unventilated double skin facade were presented.

关键词： chimney effect assessment double-skin facade

Slicing Method for Reverse engineering Based on Image Mosaic

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Computer Aided Drafting,Design and Manufacturing 2008年第2期18卷 33-38页

作者： ZHAN Yi-bin,LIN Da-jun,AN Qi (school of mechanical and power engineering, east china university of science and technology, shanghai 200237, china)

Reverse engineering dealing with images is traditionally based on image processing and contour recognition. A new method is presented based on the combination of sectional slicing with image mosaic. Sectional contours of the target object are generated by colorful liquid or laser scanning, these images from different views are fused into a set of complete cross-sectional images, thereby the whole practical model is reconstructed in 3D space.

关键词： reverse engineering image mosaic slicing contour 3D reconstruction

Nanostructural evolution of Zn by dry roller vibration milling at room temperature

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Progress in Natural science:Materials International 2006年第4期16卷 441-444页

作者： wang Shulin, LI Shengjuan, DU Yanchen, xu Bo, LI Laiqiang and ZHU Yan Department of power engineering Department of Medical Apparatus, university of shanghai for science and technology, shanghai 200093, china Department of power engineering University of Shanghai for Science and Technology Shanghai 200093 China Department of Medical Apparatus University of Shanghai for Science and Technology Shanghai 200093 China

It remains open to date to produce stable nanostructures of single element by dry mechanical method at room temperature on a large scale. Here we report nanostructural evolution of zinc by dry roller vibration milling at room temperature, which leads to structurally near perfect zinc flakes sized 3-5 nm in diameter. The synthesized nanostructures are single crystalline, transparent, uniform, randomly oriented, almost equiaxed, and mostly free from defects. The evolution seems to open a way to optimize zinc nanostructures by the mechanical method, offer valuable references to prepare nanostructures of other metals optimally, and shed light on how to lower the size limit by mechanical milling. Single elemental metal nanostructures with excellent properties give rise to new opportunities in scientific research and development of nanotechnology.

关键词： nanoparticles nanostructures vibration milling.

s-ordering operator expansions of quantum-mechanical fundamental representations and their applications

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science china(Physics,Mechanics & Astronomy) 2011年第12期54卷 2150-2154页

作者： FAN HongYi 1,3 , xu YeJun 2 & YUAN HongChun 3,4 1 Department of Materials science and engineering, university of science and technology of china, Hefei 230026, china 2 Department of Physics Electronic and engineering, Chizhou university, Chizhou 247000, china 3 Department of Physics, shanghai Jiao Tong university, shanghai 200030, china 4 College of Optoelectronic engineering, Changzhou Institute of technology, Changzhou 213002, china Department of Materials science and engineering University of Science and Technology of China Hefei China Department of Physics Shanghai Jiao Tong University Shanghai China Department of Physics Electronic and engineering Chizhou University Chizhou China College of Optoelectronic engineering Changzhou Institute of Technology Changzhou China

We show that the quantum-mechanical fundamental representations, say, the coordinate representation, the coherent state representation, the Fan-Klauder entangled state representation can be recast into s-ordering operator expansion, which is elegant in form and has many applications in deriving new operator identities. This demonstrates that Dirac's symbolic method can be merged into Newton-Leibniz integration theory in a broad way.

关键词： s-ordering operator expansion operator identities quantum mechanical representation

Numerical study on the cavity dynamics for vertical water entries of twin spheres

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Defence technology（防务技术） 2024年第2期32卷 459-472页

作者： xu wang xujian Lyu Ruisheng Sun Dongdong Tang school of Energy and power engineering Nanjing University of Science and TechnologyNanjing210094China shanghai Institute of Spacecraft Equipment Shanghai200240China

In this study, a three dimensional(3D) numerical model of six-degrees-of-freedom(6DOF) is applied to simulate the water entries of twin spheres side-by-side at different lateral distances and time *** turbulence structure is described using the shear-stress transport k-ω(SST k-ω) model, and the volume of fluid(VOF) method is used to track the complex air-liquid interface. The motion of spheres during water entry is simulated using an independent overset grid. The numerical model is verified by comparing the cavity evolution results from simulations and experiments. Numerical results reveal that the time interval between the twin water entries evidently affects cavity expansion and contraction behaviors in the radial direction. However, this influence is significantly weakened by increasing the lateral distance between the two spheres. In synchronous water entries, pressure is reduced on the midline of two cavities during surface closure, which is directly related to the cavity volume. The evolution of vortexes inside the two cavities is analyzed using a velocity vector field, which is affected by the lateral distance and time interval of water entries.

关键词： Twin water entries Side-by-side Cavity Numerical simulation

Data fusion for target tracking in wireless sensor networks using quantized innovations and Kalman filtering

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science china(Information sciences) 2012年第3期55卷 530-544页

作者： xu Jian1,2 , LI Jianxun1,2 & xu Sheng3 1Department of Automation, science and technology on Avionics Integration Laboratory, shanghai Jiao Tong university, shanghai 200240, china 2Department of Automation, System Control and Information Processing, Ministry of Education of china, shanghai Jiao Tong university, shanghai 200240, china 3school of mechanical engineering, shanghai Jiao Tong university, shanghai 200240, china Department of Automation Science and Technology on Avionics Integration Laboratory Shanghai Jiao Tong University Shanghai China Department of Automation System Control and Information Processing Ministry of Education of China Shanghai Jiao Tong University Shanghai China school of mechanical engineering Shanghai Jiao Tong University Shanghai China

A novel networked data-fusion method is developed for the target tracking in wireless sensor networks (WSNs). Specifically, this paper investigates data fusion scheme under the communication constraint between the fusion center and each sensor. Such a message constraint is motivated by the bandwidth limitation of the communication links, fusion center, and by the limited power budget of local sensors. In the proposed scheme, each sensor collects one noise-corrupted sample, performs a quantizing operation, and transmits quantized message to the fusion center. Then the fusion center combines the received quantized messages to produce a final estimate. The novel data-fusion method is based on the quantized measurement innovations and decentralized Kalman filtering (DKF) with feedback. For the proposed algorithm, the performance analysis of the estimation precision is provided. Finally, Monte Carlo simulations show the effectiveness of the proposed scheme.

关键词： data fusion target tracking limited bandwidth quantized innovation Kalman filtering