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A Multiple Model Approach to Modeling Based on LPF Algorithm

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Journal of Systems Engineering and Electronics 2001年第3期12卷 64-70页

作者： Li, N. Li, S. Xi, Y. Institute of Automation Shanghai Jiaotong University Shanghai 200030 China

Input-output data fitting methods are often used for unknown-structure nonlinear system modeling. Based on model-on-demand tactics, a multiple model approach to modeling for nonlinear systems is presented. The basic idea is to find out, from vast historical system input-output data sets, some data sets matching with the current working point, then to develop a local model using Local Polynomial Fitting (LPF) algorithm. With the change of working points, multiple local models are built, which realize the exact modeling for the global system. By comparing to other methods, the simulation results show good performance for its simple, effective and reliable estimation.

关键词： Algorithms Computer simulation Data structures Input output programs mathematical models Parameter estimation Polynomials

DOUBLE-PARAMETER PERTURBATION SOLUTION TO 3-D NONLINEAR PROBLEM OF OBLIQUE WATER EXIT

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Journal of Hydrodynamics 1991年第4期3卷 96-103页

作者： Qu-yuan, Ye You-sheng, He Shanghai Jiao Tong Univ Shanghai China

With a new time-derivative operator, the nonlinear kinematic and dynamic free boundary conditions were modified to a convenient form for numerical computation. The original 3-D nonlinear problem of oblique water exit of an axisymmetric body at a large water exit-angle and a small angle of attack is reduced to a number of 2-D problems by means of the double-parameter-series expansion method and the Fourier-cosine-expansion method. Numerical results are presented of the free surface shapes and the forces exerted during the oblique water exit of a sphere at different Froude numbers.

关键词： Flow of Water mathematical models mathematical Techniques Nonlinear Equations mathematical Techniques Perturbation Techniques

NUMERICAL SIMULATION OF WATER QUANTITY AND QUALITY FOR RIVER-TYPE RESERVOIRS

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Journal of Hydrodynamics 1995年第2期7卷 96-103页

作者： Wang, Huimin Hohai Univ Nanjing China

River-type reservoir is narrow and long in shape and has many reservoir bends and confluence of tributaries. On the basis of Saint-Venant equation and differential equation for longitudinal diffusion and in consideration of the influence of confluences and bends, in order to predict the water quantity and quality, an one-dimensional unsteady mathematical model was established in this paper. The model consists of a hydrodynamic model and a water quality model. The average hydraulic characteristics and water quality parameters were calculated for a reservoir with two confluences and four bends. Computed results are in good agreement with field observation data. The model can be applied to predict the water quantity, water level and water quality of the river-type reservoirs.

关键词： Computer simulation mathematical models Numerical methods Water quality Water resources

NUMERICAL MODEL FOR DYNAMIC SIMULATION OF TRAFFIC FLOW

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Journal of Hydrodynamics 1994年第1期6卷 1-11页

作者： Wu, Zheng Zeng, Linong Fudan Univ Shanghai China

For the purpose of practical application in traffic engineering, especially in automatic control of traffic systems, in this paper a numerical model for the dynamic simulation of traffic flow was presented, involving difference schemes, boundary conditions and their discrete forms, expressions of traffic behavior parameters and technique of modelling parameter identification. The analysis of numerical simulation for several realistic examples shows the usefulness and advantages of the model.

关键词： Computer simulation Finite difference method mathematical models Optimal control systems Traffic control Traffic surveys

ON THE RELATIONS AMONG THE DIFFERENCE SCHEMES, BOTTOM FRICTION FORMS AND NUMERICAL STABILITIES FOR 1-D UNSTEADY FLOW EQUATIONS

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Journal of Hydrodynamics 1991年第1期3卷 45-50页

作者： Wu, Zheng Fudan Univ Shanghai China

It is analysed in this paper that the relations among the difference schemes, bottom friction forms and numerical stabilities for unsteady water flow equations. The author shows some interesting results: (a) the numerical stabilities of a difference scheme cannot always be improved by introducing a bottom friction item; (b) the bottom friction forms for a nonsymmetrical numerical system must be different from that for a symmetrical one; (c) the stability criteria for the 'upwind' schemes and for the flux splitting schemes of 1-d unsteady water flow equation.

关键词： Computers Applications Flow of Water Friction Hydrodynamics mathematical models mathematical Tecniques Numerical Methods

COMPUTER-AIDED ANALYSIS OF UNSTEADY PARTIALLY FILLED FLOWS IN DRAINAGE SYSTEMS

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Journal of Hydrodynamics 1997年第4期9卷 46-52页

作者： Mao, Zeyu Chen, Changzhi Tsinghua Univ Beijing China

Partially filled pipeflows were encountered in drainage systems belonging to a family of unsteady flow problems. Basic equations were developed and numerically solved also by the characteristic different methods with time-line interpolation scheme. The boundary conditions for the inflow, outflow, moving hydraulic jump and junctions were developed experimentally and numerically. Full scale model experiments were carried out. It is consequently clarified that numerical model is capable of predicting flow characteristics in realistic drainage networks.

关键词： Computer aided analysis Drainage Flow of fluids Hydrodynamics mathematical models Unsteady flow

TWO PROCEDURE OF MODEL RELIABILITY BASED OPTIMIZATION FOR WATER DISTRIBUTION SYSTEMS

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Journal of Hydrodynamics 2000年第1期12卷 67-78页

作者： Shi, Peiying Xu, Zuxin Tongji Univ Shanghai China

Recently, a considerable emphasis has been laid to the reliability-based optimization model for water distribution systems. But a considerable computational effort is needed to determine the reliability-based optimal design of large networks, even of mid-sized networks. A new methodology which consists of two procedures is presented in this paper. The first procedure is that the optimal design is constrained only by the pressure heads at demand nodes, done in GRG2. Because the reliability constrains are removed from the optimal problem, a number of simulations do not need to be conducted and the computer time is greatly decreased. Then, the second procedure is a linear optimal search procedure. In this linear procedure, the optimal results obtained by GRG2 are adjusted by the reliability constrains. The results are a group of commercial diameters of pipes and the constraints of pressure heads and reliability at nodes are satisfied. Therefore, the computer burden is significantly decreased, and the reliability-based optimization is of more practical use.

关键词： Flowcharting mathematical models Optimization Reliability

NUMERICAL SIMULATION OF THREE-DIMENSIONAL TURBULENT FLOW NEAR BODY SURFACE WITH LONGITUDINAL VORTICES

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Journal of Hydrodynamics 1991年第1期3卷 26-36页

作者： Gao, Gao Zhao, Run-yuan Wuhan Inst of Water Transportation Engineering Wuhan China

A calculating model of generalized partially-parabolic approximation is adopted in the research of numerical simulation of 3-D turbulent flow near body surface with longitudinal vortices in this paper. An analytical solution for Poisson equation is presented to generate the 3-D body-fitted coordinate system. The finite analytic method, which introduces 'virtual' time variable, is used calculating examples. The partially-parabolic approximation is made in the transformed equations. Compared with that made in the physical domain, it allows the equations to retain more terms. In 'zero' equation turbulence model, longitudinal eddy-viscosity and transverse eddy-viscosity are determined by using empiric formulae appropriate to inner layer and outer layer respectively. Of three example calculations, the results of turbulent flow past a flat plate with longitudinal vortices are compared with that of available experimental data. The comparison is found to be satisfactory. The results of the others - turbulent flow along a long cylinder and that past an ellipsoid with longitudinal vortices, are qualitatively reasonable.

关键词： Computer Simulation Computers Applications Hydrodynamics mathematical models mathematical Techniques Differential Equations

SIMPLIFIED MODEL AND ITS APPLICATION FOR WAVEMAKING INDUCED BY EXPLOSION

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Journal of Hydrodynamics 1995年第1期7卷 33-44页

作者： Shen, Guoguang Li, Dejun Tianjin Univ Tianjin China

This paper pays attention to the analysis of overall macroscopic process of wavemaking induced by explosion. Based on establishing the simplified model and MAC method, the numerical simulations for formulating crater induced by touching water surface explosion, the bubble jumping out of the water surface induced by underwater explosion as well as hollow column formation for large equivalent explosion etc were carried out. In order to predict the wave field, the scheme simulated by falling and evoluting of an ″equivalent cylinder″ were proposed. In addition to researching the wavemaking response in a harbour, two joining methods in time domain were presented. The results indicate that the model and numerical methods are feasible.

关键词： Bubbles (in fluids) Computer simulation Explosion testing mathematical models Surface waves