Archive

25 July 2000, Volume 17 Issue 4 Previous Issue    Next Issue

---

For Selected:

Download Citations EndNote Ris BibTeX

Toggle Thumbnails

Select

NUMERICAL SIMULATION OF THE NEAR REGION OF COMPRESSIBLE AXISYMMETRIC JET LIU Ming-yu, MA Yan-wen, FU De-xun 2000, 17(4): 341-346.  Abstract ( )   PDF (401KB) ( )   The flow fields of 2-D compressible axisymmetric jet are simulated by solving N-S equations. The discretization method has high order accuracy. The information and development of the large vortical structure and it's role in the jet development are studied. The Kelvin-Helmholtz wave appears firstly when jet losts it's stability, and then the single vortex rolls up. After that, with the development of jet, the vortex structures begin to pair and merge because of the increasement of non-linear effects. It is also shown that the pressure distribution is directly relative to the large vortical structures.

Select

EQUILIBRIUM RECONSTRUCTION OF HELICITY INJECTION CURRENT DRIVE EXPERIMENT ZHANG Cheng 2000, 17(4): 347-354.  Abstract ( )   PDF (298KB) ( )   Current drive is one of the major issues in controlled nuclear fusion research field. For the steady state operation, a variety of current drive methods are under systematic investigation. Helicity injection current drive is an attractive method. The experiment on Helicity Injected Tokamak(HIT) in U.S. obtained 150 kA toroidal driven current applying the coaxial helicity injection, which is the most remarkable results. This paper reports the results about equilibrium reconstruction in the above mentioned experiment. The driven current profiles and magnetic topology are consistent with the MHD equlibrium constraint from magnetic measurement data by using EFIT equilibrium fitting code. The reconstruction shows that these plasmas have a Tokamak q profile, with a hollow toroidal current profile and up to 110 kA of closed field toroidal current in a low aspect ratio configuration. Calculation results also indicate that plasma relaxed state is a non complete relaxation state away from Taylor State.

Select

TOPOLOGICAL STRUCTURES OF FLOW PATTERNS ON PLATE SURFACE INDUCED BY VARY HEIGHT CIRCULAR CYLINDERS MA Han-dong, ZHOU Wei-jiang 2000, 17(4): 355-359.  Abstract ( )   PDF (227KB) ( )   The hypersonic flows around circular cylinders mounted flat plate are simulated by Reynolds-averaged Navier-Stokes equations and modified Baldwin-Lomax turbulence model. The zonal method and Roe third-order flux difference splitting scheme are used for the computation. The correspondent topological structures of flow patterns on plate surface are then obtained by topological theory. Some brief discussions are made with emphasizing on problems needed to be further studied.

Select

DOMAIN DECOMPOSITION METHOD AND PARALLEL COMPUTING METHOD TO SOLVE EULER EQUATIONS LU Xiao-bin, LAN Qian-zhang, ZHU Zi-qiang 2000, 17(4): 360-366.  Abstract ( )   PDF (258KB) ( )   A domain decomposition method of Euler equations is applied to a two dimensional transonic and supersonic flow. The flow region is divided into distinct regions, a zonal interface conservative technique is presented on basis of flux-vector splitting methods and characteristics theory of information propagation then interfacing these regions separately. Two dimensional transonic and supersonic flow field including arc bump and airfoils are calculated. Results of domain decomposition method are coincident very well with that of continuous single region solution. Parallel computing method using PVM parallel environment is proposed. “First-in First-out” synchronization strategy is applied in parallel programming model. An efficient method of high parallel speedup ratio is applied and influencing factors of parallel computing are disucssed.

Select

THE CALCULATION OF THE FLOWFIELD OF HELICOPTER ROTOR BASED ON MOVING GRID WANG Li-qun, SONG Wen-ping, ZHANG Ru 2000, 17(4): 367-371.  Abstract ( )   PDF (181KB) ( )   The description of the moving grid-strategy is presented. Based on transfinite interpolation, an O-H type grid around one blade is generated. In each subdomain, the weighting funtion is given to account for the time-variation of its nodes. The multi-block grid modelling the whole rotor is achieved by the construction of grid-blocks around each blade which are connected with coincident nodes on their common boundaries, the flowfield of a rotor is calculated by considering the transport of interface information. The calculated results show that the moving grid possesses feasibility and effectiveness.

Select

DOMAIN DECOMPOSITION FOR GENERALIZED STOKES PROBLEM ON NON-COINCIDENT MESHES AND A POSTERIORI ERROR ESTIMATION ZHOU Chun Hua 2000, 17(4): 372-380.  Abstract ( )   PDF (295KB) ( )   A method of domain decomposition for generalized Stokes problem is developed. The condition of compatibility on the interfaces between each subdomain is satisfied weakly by introducing a Lagrange multiplier technique. In the computational domain, the finite element meshes can be non-coincident at the interfaces. The Petrov-Galerkin formulation is applied to solve the generalized Stokes problem in each subdomain, and the Lagrange multiplier problem on the interfaces is solved using an algorithm of conjugated gradient. Velocity, density (or pressure) and Lagrange multiplier are approached in the spaces of continue piecewise linear functions. Associated with the above domain decomposition method, a local a posteriori error estimation has been constructed. The localization of the error estimation is based on solving local problems. The local error estimators respectively for velocity, density and Lagrange multiplier, are defined in the space of discontinue quadratic bump functions. At the end, some numerical results on the adaptive meshes are also given based on local a posteriori error estimation.

Select

FINITE VOLUME METHOD ON UNSTRUCTURED TRIANGULAR MESHES AND ITS APPLICATIONS ON CONVECTIVE PHENOMENA HOU Hui-qing, ZHANG Li, JIN Xi-zhuo 2000, 17(4): 381-387.  Abstract ( )   PDF (237KB) ( )   It presents a new upwind scheme on unstructured triangular meshes. The discretization of three conservation equations for mass, momentum and heat including thermodiffusion is performed using the upwind finite volume method. The two-dimensional mathematical model is used on the numerical study of convective phenomena in non parallel wall channels. Similarly, the numerical results presented can also be used to predict thermal conductivity and diffusion and momentum transport phenomena in the kind of duct.

Select

SIMULATIONS OF COMPRESSIBLE PERFECT GAS FLOW BY LATTICE-BOLTZMANN MODELS SUN Cheng-hai 2000, 17(4): 388-394.  Abstract ( )   PDF (223KB) ( )   A new adaptive lattice Boltzmann model is presented to simulate super-sonic flows. Particle velocities may have a large range of values. The support set of equilibrium distributions is determined by the mean velocity and internal energy. The adaptive nature of particle velocities permit the mean flow to have a high Mach number. A particle potential energy is introduced to make the model suitable for the perfect gas with arbitrary specific heat ratio. Navier-Stokes equations are derived by the Chapman-Enskog method from the BGK Boltzmann equation. As numerical test, the simulation is performed for a flow passing over a forward-facing step at Mach number 3 on a hexagonal lattice. The shocks are well captured.

Select

LATTICE GAS AUTOMATON SIMULATION OF STANDING SOUND WAVES IN A TWO-DIMENSIONAL PIPE LI Gen-qiang, CHEN Yu, MA Hong-bo 2000, 17(4): 395-400.  Abstract ( )   PDF (209KB) ( )   A 9_Bit square lattice gas model with temperature was introduced. We fulfilled an acoustic driver using Monte Carlo Method. Using this driver to generate plane waves, a standing sound wave was established in a two-dimensional pipe. This model can display the formation and change of the standing wave in real time and combined with its ability to simulate temperature variations, other phenomena, such as thermoacoustic, can be further analized on the microscopic level.

Select

HIGH-ORDER PCG METHOD SOLVING COMPLEX SYSTEMS HUANG Zhao-hui, LEI Guang-yao, LIU Xing-ping 2000, 17(4): 401-406.  Abstract ( )   PDF (186KB) ( )   To solve complex systems obtained from 2D nonlinear Schrödinger equation, a method of high-order PCG coupling with BICG has been developed. Meanwhile, the complex systems of order M can be reconstructed as the real systems of order 2M. From the theory of order matrix, the high order approximate LU decompositions are given as the preconditioners to solve the real systems. Numerical results show that the computational efficiency can be nearly doubled by the high-order PCG method comparing with the ICCG method.

Select

COMPUTER SIMULATION FOR THE ATTRACTOR OF THE ITERATIVE FUNCTION SYSTEMS WANG Xing-yuan, ZHU Wei-yong 2000, 17(4): 407-413.  Abstract ( )   PDF (372KB) ( )   It expounds the iterative function systms (it is called IFS for short) theory and the deterministic algorithm. A series of the fractal IFS attractors are simulated by utilizing the computer. The changing regularity of the IFS attractors are discussed when the control parameters are changed, and the fractal dimension of some attractors are reached by the theorem about the fractal dimension of the IFS attractor.

Select

COMPUTATIONS OF SCATTERING WAVES IN 2-D COMPLICATED FIELDS BY USING EXACT CONTROLLABILITY APPROACH CHEN Hong quan, HUANG Ming ke 2000, 17(4): 414-420.  Abstract ( )   PDF (386KB) ( )   An exact controllability approach is used for the calcuation of time periodic solutions of the wave equation, which is proved to be equivalent to the Maxwell equation in two dimensions for the T.M.mode. The numerical results of scattered fields and Radar cross sections(RCS) are presented for complicated aerodynamic shapes with cavity, external obstacle or a slender body. The method presented has the ability to deal with more complicated aerodynamic shapes due to the use of unstructure triangulations.

Select

THE ANALYSIS OF SEVERAL FLUX SPLITTING SCHEME BASED ON SPLINE INTERPOLATION FINITE VOLUME SCHEME WANG Jian-li, REN Yu-xin, SHEN Meng-yu 2000, 17(4): 421-425.  Abstract ( )   PDF (288KB) ( )   High order accurate, non-oscillating finite volume schemes using spline interpolation for solving conservation laws in arbitrary curvilinear coordinate are analyzed and three different flux splitting schemes are compared. Numerical experiment indicates that these schemes are of high resolution to shock and contact discontinuities.

Select

CALCULATIONS OF COMPLETE CLASSIFICATION FOR g-SHELL LSQ COUPLED STATES BY EIGENVALUES OF SCALAR OPARATOR LI Xiao-mei, CHEN Jian-hua 2000, 17(4): 426-432.  Abstract ( )   PDF (249KB) ( )   The LSQ coupled states of l-shell are constructed by (U,D)L-LSQ scheme, where U(D) is the total orbital angular momentum of spin up(down) electrons, the LS and Q are the total orbital angular momentum, spin and quasispin respectively, the (U,D) L-LSQ is unitary transformation. The scalar operators which commute with the total orbital angular momentum, spin and quasispin operators, are constructed from 4 creation-annihilation operators, and the LSQ coupled states are further or complete classified by its eigenvalues. The complete classifications of coupled states for f- and g-shell are obtained, the primary results of complete classifications of coupled states for g-shell are listed.

Select

ELECTRONIC STRUCTURE AND ALLOY BEHAVIORS OF HIGH Co-Ni SECONDARY HARDENED MARTENSITIC STEELS ZHANG Guo-ying, ZENG Mei-guang, LIU Gui-Li, QIAN Cun-Fu 2000, 17(4): 433-437.  Abstract ( )   PDF (193KB) ( )   The electronic structure of high Ni-Co secondary hardening martensitic steel has been investigated by the recursion method in the tight-binding approximation. The local density of states(LDOS) of alloying elements in two kinds of structure (with carbon or without carbon) have been caculated. By the integration of the total density of states(TDOS), the Fermi energy of system, the bond order integral(BOI) between atoms are presented for alloying steel. On the basis of these results, the bonding characteristics, the physical properties as well as the influence of different alloying elements on physical properties of high Ni-Co secondary hardening martensitic steel are discussed.

Select

MOLECULAR DYNAMICS METHOD OF GAS-SURFACE INTERACTION:STICKING AND DESORPTION OF XENON ATOMS FROM THE PLATINUM SURFACE HUANG Lin, CHEN Wei-fang, WU Qi-fen, REN Bing 2000, 17(4): 438-442.  Abstract ( )   PDF (180KB) ( )   The molecular dynamics method is employed to study the sticking and desorption of Xenon atoms from a platinum surface.After constructing correct gas-surface interaction potential,the stochastic classic trajectory method is adopted to solve the motion equation of both gas and solid atoms,then the trajectory and behavior of gas atoms can be obtained.The results show that the sticking probability depends on such factors as wall temperature,gas atom incident enenrgy and interaction potential parameters etc.,the thermal desorption rate of gas atoms from platinum surface satisfies Arrhenius correlation.

Select

NUMERICAL SIMULATION METHOD OF NEGATIVE ION BEAM EXTRACTION AND ACCELERATION SYSTEM JIAN Guang-de, WANG Hui-san 2000, 17(4): 443-448.  Abstract ( )   PDF (284KB) ( )   A mathematical model for numerically simulating high current negative ion beam extraction and acceleration system has been established in order to assistantly design.The related computation method is described briefly.The electric and magnetic field conformation in the system is optimized and the initial optimized results of the 300 keV、5 electrodes negative ion beam system is given as well.

Select

INFLUENCE OF SURFACE TRENCH ON UNIFORMITY OF PLASMA IMMERSION ION IMPLANTATION ZENG Zhao-ming, TANG Bao-yin, WANG Song-yan, TIAN Xiu-bo, LIU Ai-guo, WANG Xiao-feng, CHU Paul K 2000, 17(4): 449-454.  Abstract ( )   PDF (207KB) ( )   The sheath expansion around a planar target with an arc trench during plasma immersion ion implantation(PⅢ) is simulated numerically with a two-dimensional fluid model.The sheath potential,ion velocity and ion density during sheath expanding are calculated.The distribution of ion incident angle and dose along the target surface is presented.It provides the theoretical base for treatment of the targets with complicated shape using plasma immersion ion implantation.

Select

GIBBS ENSEMBLE MONTE-CARLO SIMULATION AND ITS APPLICATION WANG Ke-gang, SIEPMANN I 2000, 17(4): 455-458.  Abstract ( )   PDF (159KB) ( )   It introduces a Gibbs Ensemble Monte-Carlo method,which was recently invented.This method has been applied for studying the phase diagrams of Lennard-Jones mixtures,and Methane and Tetrafluoromethane.The obtained results of simulations are in good agreement with experimental and previous results.

Select

THE RESEARCH ON INTERACTIVE GRID GENERATION TECHNIQUE WU Zong-cheng, ZHU Zi-qiang, CHEN Ze-min, LI Jin, YAN Zhi 2000, 17(4): 459-464.  Abstract ( )   PDF (437KB) ( )   An interactive method of block grid generation is studied, including the issues of interactive input, graphics view, grid quality check, visual random control of grid solving process, etc. An interactive generation system-BIGG is developed by the above techniques. The numerical results of grid generation and flow solution indicate that the interactive technique presented is feasible and effective, the system-BIGG improves the generation efficiency and grid quality.