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25 September 2001, Volume 18 Issue 5 Previous Issue    Next Issue

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A PARALLEL COMPUTING METHOD FOR BURGERS EQUATION WANG Wen-qia 2001, 18(5): 385-389.  Abstract ( )   PDF (143KB) ( )   A kind of alternating segment Crank Nicolson method for solving Burgers equation is presented. The method is uncoditionally stable by analysis of linearization procedure and has the intrinsic parallelism with high accuracy.

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NUMERICAL SIMULATION OF RICHTMYER-MESHKOV INSTABILITYOF DENSITY-STRATIFIED INTERFACE OF LIGHT-GAS CYLINDER CHENG Jun-bo, FU De-xun, MA Yan-wen 2001, 18(5): 390-396.  Abstract ( )   PDF (300KB) ( )   An approach combining the fifth Upwind Compact Difference Scheme and Group Velocity Control is applied to simulate directly the interaction of shocks and the density stratified interface of light-gas cylinder.Some research about the generation and development of vorticity and the distortion of edge of cylinder is done.The instability of cylinder density-interface is analyzed.Main character of the linear developing phase is that the gas of higher density goes into the one of lower denstiy at a constant velocity and the spike structure is formed and the character of the nonlinear developing phase is that a pair of vortex structures rotating adversely are formed on both sides of the top of the spike.The numerical solution accords with the experiment.

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A METHOD TO SIMULATE THE AEROELASTIC PROBLEM BASED ON NAVIER-STOKES EQUATIONS YE Zheng-yin, WANG Gang, YANG Yong-nian, YANG Bin-yuan 2001, 18(5): 397-401.  Abstract ( )   PDF (194KB) ( )   A dual-time scheme is used to solve the unsteady compressible Navier-Stokes equations to obtain the needed airload.The model structural equations of motions are computed simultaneously using the Runge-Kutta method to calculate the aeroelastic static deformations and responses of wings in the time-domain.The O-H type grid around the deforming wings is generated using the improved transfinite interpolation method so that grid generation in each time-step is not too time-consuming.The numerical results show the transonic flutter speed drop and nonlinear characteristics.

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GENERATION OF THREE-DIMENSIONAL USTRUCTURED VISCOUS GRIDS WANG Gang, YE Zheng-yin, CHEN Ying-chun 2001, 18(5): 402-406.  Abstract ( )   PDF (365KB) ( )   A method for generating three-dimensional unstructured viscous grids automatically is presented. High-aspect-ratio and anisotropic tetrahedral grid cells are constructed in viscous dominated flow regions by advancing-layers method (ALM).When the height of viscous grids reaches the requirement,the conventional advancing-front method (AFM)will generate isotropic grids to fill the remained flow regions.By the control of stretched function and background information,the transition from grids generated by ALM to isotropic grids generated by AFM becomes smooth and gradual.The unstructured viscous grids of M6 wing and the simple flow results of corresponding Navier-Stokes solution based on the present grid are also provided.

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THE LATTICE BOLTZMANN MODEL OF A COMPLETE CONSERVATION FORM FENG Shi-de, REN Rong-cai, MAO Jiang-yu 2001, 18(5): 407-411.  Abstract ( )   PDF (206KB) ( )   Three kinds of particle granules are included in each hexagonal cell using a discrete method of hexagonal lattice,and macroscopic quantities are defined by the moment of particle granules.Two-dimensional D2Q19-lattice Boltzmann model has been developed by the conservation laws of mass,momentum and energy,and the hydrodynamic equations can be derived from the model.The shock wave reflection phenomena on the surface of obstacles have been simulated using the model.

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FREQUENCY RESPONSE OF CELL CALCIUM OSCILLATION AND SYNCHRONIZATION YING Yang-jun, HUANG Zu-qia 2001, 18(5): 412-416.  Abstract ( )   PDF (231KB) ( )   Based on the intercellular calcium concentration oscillations model proposed by Somogyi R and Stucki J W in 1991,its response to external periodic stimulations and the synchronization of the oscillations between two cells with different intrinsic frequencies connected by intercellular gap junction are simulated.

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DOMAIN DECOMPOSITION METHODS BASED ON NATURAL BOUNDARY REDUCTION FOR WAVE EQUATION DU Qi-kui, YU De-hao 2001, 18(5): 417-422.  Abstract ( )   PDF (234KB) ( )   Some new domain decomposition methods based on natural boundary reduction are suggested for overlapping and non-overlapping domains. A two-dimensional scalar wave equation is taken as a model to illustrate these methods. The governing equation is discretized in time, leading to time-stepping scheme, where an exterior elliptic problem has to be solved in each time step. The Dirichlet-Neumann method and Schwartz alternating method are proposed respectively. For the Schwartz alternating method, the convergence of the algorithm and the contraction factor for exterior circular domain are given. Finally, some numerical examples are devoted to illustrate these methods.

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MULTIGRID SOLVER BASED ON THE DEFECT EQUATION HUANG Zhao-hui, CHANG Qian-shun 2001, 18(5): 423-428.  Abstract ( )   PDF (244KB) ( )   A new approach for producing the MG interpolatory formula is proposed on the basis of the defect equation. This new interpolatory formula makes full use of information of coarser grids, and thus has higher accuracy. Numerical experiments for Poisson equation, anisotropic equation, biharmonic equation, and even 3D problem show that the new interpolatory formula improves the asymptotic convergence rate, and reduces the storage capacity and computational time for the AMG method.

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A SPLINE APPROXIMATING ALGORITHM FOR THE REZONING (REMAPPING) OF ARBITRARY MESHES WANG Rui-li, MAO Ming-zhi 2001, 18(5): 429-434.  Abstract ( )   PDF (224KB) ( )   The method in computational fluid dynamics requires the periodic remapping of conservation quantities such as mass, momentum, and energy from old or distorted meshes to some other arbitrarily defined meshes. This is a type of interpolation procedure, which is usually constrained to be conservative and monotone. A type of remapping algorithms using spline-approximating methods are presented for numerical simulation codes applied to unstructured or adaptive meshes.

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FITTING SURFACES TO SCATTERED DATA AND SOFTWARES MAO Ming-zhi, HU Ri-zhang 2001, 18(5): 435-438.  Abstract ( )   PDF (135KB) ( )   Surface fitting and software to scattered data are concerned.Some efficient algorithms are presented for interpolating and smoothing scattered data on two and three-dimensional domains by splines.The methods can be extended to any multi-dimensional cases and are easily performed on a computer by solving a symmetric linear algebraic system coefficient matrix,order of which is dependent on the number of the data and independent of the dimension of variables.The programs executing the algorithms are designed with Delphi 3^0.The software can output values on any points of the three-dimensional graph of the surface.Some numerical examples (graphs) illustrate the effectiveness of the software.

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A NUMERICAL GENERATING METHOD FOR GLOBAL HOMEOMORPHIC GRID FROM TOWEL-SHAPED REGION TO SQUARE COMPUTATIONAL REGION WANG Ru-yun, FANG Guo-hong, ZHANG Dong-sheng, ZHANG Chang-kuan, ZHANG Jun-lun 2001, 18(5): 439-442.  Abstract ( )   PDF (158KB) ( )   The numerical generating method for global homeomorphic grid from multi-dimensional towel-shaped reality region to square computational region is investigated. The numerical iterative method for multi-dimensional equal-parameter transformation is given. Its error analysis and the sufficient condition of numerical grid without overlapping is pressented. Finally, an example about two-dimensional non-overlapping numerical grid generation for Qiantang Estuary is shown.

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THE MOLECULAR FIELD THEORY OF THIN LIQUID CRYSTAL FILMS CONFINED BY TWO RUBBED SUBSTRATES ZHANG Zhi-dong, KONG Hao, XUE Shan-ling 2001, 18(5): 443-446.  Abstract ( )   PDF (182KB) ( )   A new surface potential form is proposed to describe the action of the rubbed substrate to the liquid crystal molecules. By means of the molecular field theory, thin liquid crystal films confined by two rubbed substrates which lead to a homogeneous planar alignment of the liquid crystal molecules are studied. Adopting the Lebwohl-Lasher model,the molecular centers of mass are located at the sites of a simple cubic lattice. Numerical calculations are made for a liquid crystal film composed of 20 molecular layers. Three states with the different preferred directions of the molecular orientations exist and the one oriented along the rubbed direction has the lowest free energy. In addition, the symmetry of the biaxiality induced by the surface action is considered.

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THE DYNAMIC RESPONSE OF THE IPS-CHIRAL-PLANAR LIQUID CRYSTAL CELL SUN Yu-bao, ZHANG Zhi-dong, MA Hong-mei 2001, 18(5): 447-450.  Abstract ( )   PDF (157KB) ( )   Based on Ericksen-Leslie's elastic theory and dynamic theory, the responsive time parameter of the in-plane switching liquid crystal displays is analyzed, the chiral-planar alignment is introduced into this mode, and the dynamic equation of the director is given. The relation of the responding time and the twist angle is obtained by calculating the instantaneous distribution of the director in this mode. The computational result demonstrates that there is a short responding time in IPS-Chiral-Planar liquid crystal cell with a certain twist angle.

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PARTIAL FLUX EXPANSION TECHNIQUES FOR SOME ADVANCED NODAL METHODS CHENG Ping-dong 2001, 18(5): 451-456.  Abstract ( )   PDF (228KB) ( )   The partial flux expansion techniques are compared and evaluated among the nodal expansion method (NEM),the nodal Green's function method (NGFM),and the nodal Fourier expansion method (NFEM).The numerical results and analyses confirm that the accuracy of NFEM is higher than any finite-order NEM and is comparable with NGFM.

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RELATIVISTIC SELF-FOCUSING OF LASER PROPAGATIONIN UNDERDENSE PLASMA YU Li-chun, TU Qin-fen, YU Wei, CHEN Zhi-hua, HAN Xue-an 2001, 18(5): 457-462.  Abstract ( )   PDF (216KB) ( )   Some natures have been studied for the propagation process of very intense and very short laser pulse in underdense plasma.The wave equation is derived and solved using the method of 2-D Fast Fourier Transformation.The basic equations for relativistic self-focusing include the nonlinear source term and the effect of diffraction.As a result of ponderomotive forces and relativism,the plasma frequency is reduced and so the refractive index is changed.It affects the propagation of laser in plasma.When the incident laser power (p) exceeds the critical power (pc),self-focusing appears during the propagation of laser.On the contrary,laser damps gradually and self-focusing doesn't appear.

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COMPUTATION FOR COLOR IMAGE RENDERING TANG Ji-yu, SANG Zi-qin, LUO Zhong-jie 2001, 18(5): 463-466.  Abstract ( )   PDF (292KB) ( )   The numerical computional method for color image rendering,which aims to calculate the tristimulus values of vision responses from the surface reflecting spectral power distribution in the scene,is presented.The linear model is exploited to approximate the reflecting continuous spectrum of the object surface and the numerical computation is conducted via Gaussian quadrature (GQ) and Riemannian summation (RS).The tristimulus values are converted to chromatic coordinates which match the images captured by CCD camera.

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CALCULATION OF TiN/VN SUPERLATTICE SHEAR ELASTIC MODULE LI Cheng-bin, LIU Fu-qing, JIAO Shu-qing, FAN Xiang-jun 2001, 18(5): 467-469.  Abstract ( )   PDF (125KB) ( )   The energy band structure of TiN/VN superlattice thin film is calculated using the pseudopotential method.The total energy of the TiN/VN superlattice cell is also calculated.Then the relationship between C44 and the period of superlattice λ is obtained.The superlattic period where C44 reaches the maximum basically accords with the experimental data.

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MONTE CARLO SIMULATION OF THE PRINCIPLE OF A NEW SCANNING ELECTRON MICROSCOPE JIANG Chang-zhong, LI Cheng-bin 2001, 18(5): 470-472.  Abstract ( )   PDF (127KB) ( )   According to the principle of a new scanning electron microscope and the mechanism of the interaction between electron beam and solid target,the trajectories of an incident electron in a sample are simulated,a simulation program is compiled using the Monte Carlo method,and the backscattering coefficients corresponding to different parameters of the SEM are obtained.

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NUMERICAL METHODS OF THREE-DIMENSIONAL PENNESEQUATION USING PARTICULAR SOLUTION BEM AND THEIR APPLICATIONS LIU Zhao-xia, WU Sheng-chang, CHANG Qian-shun, HUANG Zhen-kan 2001, 18(5): 473-476.  Abstract ( )   PDF (133KB) ( )   Particular solution BEM is used to solve three-dimensional Pennes equation.The solution is devided into the common solution of Poisson equation and the particular solution.The common solution is solved by BEM while the particular solution is given by the method of separation of variables.Temperature and heatflux are computed piecewisely in each time step and then the value on the nods in the field is computed.Numerical simulation of cancer hypothermia is given based on this method.

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BUFFET CHARACTERISTICS OF SUPERCRITICALAIRFOIL AT TRANSONIC FLOW MU Rang-ke, YANG Yong-nian, YE Zheng-ying 2001, 18(5): 477-480.  Abstract ( )   PDF (163KB) ( )   The 2-D time-dependent compressible Navier-Stokes equations are adopted as the governing equations. The unsteady lift coefficients of airfoil are calculated by Navier-Stokes equations with the implicit LU-NND algorithm, Baldwin-Lomax turbulent model and C-type grids. The fluctuating values of lift coefficient are increased with the enlargement of incidence and Mach number. The buffet onset boundary is defined as the beginning point where the fluctuating values of aerodynamic coefficients are increased suddenly. The fluctuating values of aerodynamic coefficients expresses the buffet strength. The buffet characteristics of supercritical airfoil DFVLR-R2 and airfoil NACA0012 are investigated. The calculating results show that:in the design Mach number range of supercritical airfoil, there are larger buffet onset incidence and less buffet loads. When Mach number is larger than the design Mach number, the buffet onset incidence of supercritical airfoil decreases quickly and there are rather large buffet loads. In the convention airfoil NACA 0012, there are much less buffet onset incidence, larger buffet loads and separated range.