检索结果-南通市图书馆

Journal of Hydrodynamics 2011年第1期23卷 55-64页

作者： ZOU Lin LIN Yu-feng lu Hong School of mechanical and Electronic engineering Wuhan University of Technology Wuhan 430070 China department of mechanical engineering The Hong Kong Polytechnic University Hong Kong China

A three-dimensional numerical investigation of cross-flow past four circular cylinders in a diamond arrangement at Reynolds number of 200 is carried *** the spacing ratios（L /D）ranging from 1.2 to 5.0,the flow patterns can be classified into three basic *** critical spacing ratio for the transition from narrow gap flow pattern to vortex impingement flow pattern around the cylinders is found to beL /D=3.0,while a single bluff-body flow pattern is observed atL /D=*** relationship between the three-dimensional flow patterns and force characteristics around the four cylinders shows that the variation of forces and Strouhal numbers againstL /D are generally governed by these three kinds of flow *** is concluded that the spacing ratio has important effects on the development of the free shear layers about the cylinders and hence has significant effects on the force and pressure characteristics of the four cylinders with different spacing ratios.

关键词： four cylinders spacing ratio flow pattern force characteristics

PROPULSIVE PERFORMANCE AND VORTEX SHEDDING OF A FOIL IN FLAPPING MOTION

在线全文

学校读者我要写书评

暂无评论

Journal of Hydrodynamics 2003年第5期15卷 7-12页

作者： Yang Yan, lu Xi yun, Yin Xie zhen department of Mechanics and mechanical engineering, University of Science and Technology of China, Hefei 230026, China, department of Mechanics and mechanical engineering University of Science and Technology of China Hefei 230026 China

The propulsive performance and vortex shedding of oscillating foil, whichmimics biological locomotion, were numerically investigated. The objectives of this study were todeal with unsteady force, in particular thrust force, exerted on the foil in pitching and plungingmotions, and to explore the relation of the propulsive performance with vortex structures near thefoil and vortex shedding in the near wake. The two-dimensional incompressible Navier-Stokesequations in the vorticity and stream-function formulation were solved by fourth-order essentiallycompact finite difference schemes for the space derivatives and a fourth-order Runge-Kutta schemefor the time advancement. To reveal the mechanism of the propulsive performance, the unsteady forceand the shedding of the trailing- and leading-edge vortices of the foil were analyzed. The effectsof some typical factors, such as the frequency and amplitude of the oscillation, the phasedifference between the pitching and plunging motions, and the thickness ratio of the foil, on thevortex shedding and unsteady force were discussed.

关键词： vortex dynamics vortex shedding thrust force unsteady flow flappingmotion

AN INVESTIGATION OF TURBULENT HEAT TRANSFER IN CHANNEL FLOWS BY LARGE EDDY SIMULATION

在线全文

学校读者我要写书评

暂无评论

Journal of Hydrodynamics 2002年第2期14卷 29-35页

作者： Dong Yu-hong, Zhong Feng-quan, lu Xi-yun, Zhuang Li-xian department of Mechanics and mechanical engineering, University of Science and Technology of China, Hefei 230026, China department of Mechanics and mechanical engineering University of Science and Technology of China Hefei 230026 China

Large Eddy Simulation (LES) of fully developed turbulent channel flow with heat transfer was performed to investigate the effects of the Reynolds number on the turbulence behavior. In the present study, the bottom wall of the channel was cooled and the top wall was heated. The Reynolds numbers, based on the central mean-velocity and the half-width of the channel, were chosen as 4000, 6000, 10 4 and 2×10 4, and the Prandtl number as 1.0. To validate our calculations, the present results were compared with available data obtained by Direct Numerical Simulation (DNS), which proves to be in good agreement with each other. To reveal the effects of the Reynolds number, some typical quantities, including the velocity fluctuations, temperature fluctuation, heat fluxes and turbulent Prandtl number, were studied.

关键词： Large Eddy Simulation (LES) turbulent channel flow Subgrid Scale (SGS) model heat transfer stratified turbulence

FREE-SURFACE WAVES AND FAR WAKES GENERATED BY A FLOATING BODY IN A VISCOUS FluID

在线全文

学校读者我要写书评

暂无评论

Journal of Hydrodynamics 2003年第4期15卷 10-16页

作者： lu Dong-qiang department of mechanical engineering, The University of Hong Kong, Hong Kong, China Shanghai Institute of Applied Mathematics and Mechanics, Shanghai University, Shanghai 200072, China department of mechanical engineering The University of Hong Kong Hong Kong China Shanghai Institute of Applied Mathematics and Mechanics Shanghai University Shanghai 200072 China

The free-surface waves and the flow field due to a body moving on the surfaceof an incompressible viscous fluid of infinite depth were studied analytically. The floating bodywas modeled as a normal point pressure on the free surface. Based on the Oseen approximation forgoverning equations and the linearity assumption for boundary conditions, the exact solutions inintegral form for the free-surface elevation, the velocities and the pressure were given. Byemploying Lighthill's two-stage scheme, the asymptotic representations in far field for largeReynolds numbers were derived explicitly. The effect of viscosity on the wave profiles was expressedby an exponential decay factor, which removes the singular behavior predicted by the potentialtheory.

关键词： free-surface waves velocity distribution floating body viscosity asymptotic representation light-hill's two-stage scheme

ADAPTIVE LEARNING CONTROL OF CUTTING PARAMETERS FOR SCULPTURED SURFACE CUTTING BASED ON GENETIC ALGORITHMS AND NEURAL NETWORK

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of mechanical engineering 2002年第2期15卷 145-148页

作者： Fu Hongya Wang Yongzhang lu Hua Fu Yunzhong department of mechanical engineering, Harbin Institute of Technology, Harbin 150001, ChinaTakaaki Nagao University of Tokyo, Japan department of mechanical engineering Harbin Institute of Technology Harbin 150001 China ***

An adaptive learning control scheme intended to the on-lineoptimization of sculptured. The scheme uses a back-propagation neuralnetwork to learn the relationships between process inputs and processstates. The cutting parameters of the process model are optimizedthrough a genetic algorithms(GA). The capacity of the proposed schemefor determining optimum process inputs under a variety of processconditions and optimization strategies is evaluated on the basis ofmilling of a sculptured surface using a ball-end mill. Theexperimental results show that the neural network could model thecutting process efficiently, and the cutting conditions such asspindle speed could be regulated for achieving high efficiency andhigh quality. Therefore the proposed approach can be well applied tothe manufacturing of dies and molds.

关键词： neural network genetic algorith surface cutting

DEVELOPMENT AND APPLICATION OF ADAPTIVE MESH TECHNIQUE IN THREE DIMENSIONAL NUMERICAL SIMULATION OF WELDING PROCESS

在线全文

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English Letters) 2000年第1期13卷 33-39页

作者： Q. Y.Shi A. L. lu H. Y.Zhao A.P. Wu (department of mechanical engineering, Tsinghua University, Beijing 100084, China)

The adaptive mesh mesh technique is developed and applied in three dimensional numerical simulation of welding process on the base of the commercial software. Special user subroutine is worked out to accom- plish this *** technique can make the dense mesh moving simultaneously with the heat source while the other area of the structure with much coarser mesh, greatly reducing the number of nodes and elements in the *** field,displacement and stress distributions during welding pro- cess me analyzed by FEM method with adaptive mesh and the analysis is also conducted with normal FEM method. The temperature field,displacement and stress distributions obtained with both methods are shown in contrast. The results show that the temperature fields and the displacement distributions of simulation on adaptive mesh correspond wery well with that of without adaptive mesh. Though the stress distributions have some difference,but the trends of the stress distribution are *** com- parison of the computing time of the two meshes indicates that the adaptive that the adaptive mesh can greatly reduce the calculation time when used for welding process.

关键词： adaptive mesh numerical simulation,temperature distribution,welding stress,welding displacement

Influence of Heating Rate on Double Reversible Transformation in CuZnAlMnNi Shape Memory Alloy

在线全文

学校读者我要写书评

暂无评论

Rare Metals 2001年第2期20卷 117-120页

作者： Yujun Bai, Chengwei lu, Xiangang Xu, Guili Geng, Longwei Yin (mechanical department, Shandong University of Science and Technology, Jinan 250031, China Institute of Materials Science and engineering, Shandong University, Jinan 250061, China) Shandong Univ Sci & Technol Dept Mech Jinan 250031 Peoples R China Shandong Univ Inst Mat Sci & Engn Jinan 250061 Peoples R China

The influence of heating rate on double reversible transformation in CuZnAlMnNi shape memory alloy was investigated by differential scanning calorimetry. It was found that rapid heating inhibits X -->M transformation but is favorable to the reverse martensite transformation, giving rise to the approach of the two transformation peaks. With the decrease of heating rate, the two transformation peaks separate gradually.

关键词： double reversible transformations heating rate CuZnAlMnNi shape memory alloy differential scanning calorimetry

ANALYSIS OF HYDRODYNAMICS FOR TWO-DIMENSIONAL FLOW AROUND WAVING PLATES

在线全文

学校读者我要写书评

暂无评论

Journal of Hydrodynamics 2007年第1期19卷 18-22页

作者： ZHANG Cheng ZHUANG Li-Xian lu Xi-Yun department of Mechanics and mechanical engineering University of Science and Technology of China Hefei 230026 China

Hydrodynamic characteristics for two-dimensional flow around a waving plate are investigated. Under large Reynolds number approximation, the flow is assumed to be a combination of the outer potential flow and a thin vortex layer, which consists of a boundary layer and a shed free shear layer. A nonlinear mathematical formulation for describing the outer unsteady potential flow coupled with an unsteady boundary layer equation for the inner viscous flow adjacent to the waving plate is developed. A semi-analytical method with a nonlinear Kutta condition imposed at the trailing edge is used to solve the velocity field of the outer flow and the evolution of wake vortex induced by a large-amplitude waving plate. The unsteady boundary layer equation is solved by extending Pohlhausen＇s method to its unsteady counterpart. The thrust and viscous drag coefficients, propulsive efficiency, and the pattern of wake vortex sheet are discussed.

关键词： waving plate fish swimming unsteadyboundary layer vortex shedding

Extended multiscale finite element method for mechanical analysis of heterogeneous materials

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica Sinica 2010年第6期26卷 899-920页

作者： Hong-Wu Zhang·Jing-Kai Wu·Jun L·Zhen-Dong Fu State Key Laboratory of Structural Analysis for Industrial Equipment, department of engineering Mechanics, Faculty of vehicle engineering and Mechanics, Dalian University of Technology,Dalian 116024,China State Key Laboratory of Structural Analysis for Industrial Equipment Department of Engineering Mechanics Faculty of Vehicle Engineering and Mechanics Dalian University of Technology Dalian China

An extended multiscale finite element method （EMsFEM） is developed for solving the mechanical problems of heterogeneous materials in *** underlying idea of the method is to construct numerically the multiscale base functions to capture the small-scale features of the coarse elements in the multiscale finite element *** the basis of our existing work for periodic truss materials, the construction methods of the base functions for continuum heterogeneous materials are systematically introduced. Numerical experiments show that the choice of boundary conditions for the construction of the base functions has a big influence on the accuracy of the multiscale solutions, thus,different kinds of boundary conditions are proposed. The efficiency and accuracy of the developed method are validated and the results with different boundary conditions are verified through extensive numerical examples with both periodic and random heterogeneous ***, a consistency test of the method is performed numerically. The results show that the EMsFEM can effectively obtain the macro response of the heterogeneous structures as well as the response in micro-scale,especially under the periodic boundary conditions.

关键词： Extended multiscale finite element method Heterogeneous material Base function Downscaling computation