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25 September 2004, Volume 21 Issue 5 Previous Issue    Next Issue

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Parallel Computation for Molecular Dynamics Simulation Based on Cell-Block Data Strucutres CAO Xiao-lin, MO Ze-yao, ZHANG Jing-lin, CHEN Qi-feng 2004, 21(5): 377-385.  Abstract ( )   PDF (581KB) ( )   A scalable parallel algorithm especially for large-scale three dimensional simulations with seriously non-uniform molecular distributions is presented. In particular, based on cell-block data structures, this algorithm uses space filling curve to convert three-dimensional domain decomposition for load distribution across processors into one-dimensional load balancing problems for which run-time measurement-based multilevel averaging weights method can be applied successfully. Parallel numerical experiments for simulations of three-dimensional metal-eject physical models with 210 million particles using 500 processors of one massively parallel processors have shown that this algorithm has achieved speedup about 420.

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Structure Preserving Algorithms for Soliton Equations WANG Yu-shun, WANG Bin, JI Zhong-zhen 2004, 21(5): 386-400.  Abstract ( )   PDF (720KB) ( )   The structure preservind difference algorithms for soliton equations are investigated. The symplectic structures and multisymplectic structures of the classical solitary wave equations such as the KdV, sine-Gordon and KP equations are presented to illustrate the applicability of the symplectic and multisymplectic algorithms. The concept of local conservative schemes and generalized structure preserving algorithms, which are natural generalizations of the structure preserving algorithms, are also proposed. A new concatenating method to systematically construct local conservative schemes and some numerical experiments of the constructed schemes are also presented.

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A Domain Decomposition Method Based on Mortar Elements for Incompressible Navier-Stokes Equations ZHOU Chun-hua 2004, 21(5): 401-407.  Abstract ( )   PDF (347KB) ( )   At first,the domain decomposition method based on mortar element is introduced briefly,which takes advantage of the variational principles and is well suitable for finite element approximation.Then,the emphasis is put on the application to the solution of Navier-Stokes equations for incompressible viscous flow,including construction of the equivalent variational formulation,time discretization by operator splitting,conjugate gradient iterative solution to the generalized Stoke problem with domain decomposition and finite element approximation.Finally,the results of numerical experiments validate the application of this domain decomposition method to the incompressible Navier-Stokes equations.

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Numerical Simulation of Gaseous Detonation Wave Propagation Through Bends with a Detailed Chemical Reaction Model HU Zong-min, MU Qian-hui, ZHANG De-liang, JIANG Zong-lin 2004, 21(5): 408-414.  Abstract ( )   PDF (402KB) ( )   The chemically reacting flow-field of a detonation wave in a bend is simulated by CFD method. The dispersion-controlled dissipative scheme (DCD) is adopted to solve two-dimensional Euler equations implemented with detailed chemical reaction kinetics of hydrogen-oxygen-argon mixture. The fractional step method is applied to treat the stiff problem arising from computation of chemical reaction flow. From the numerical results it is observed that as the curvature of the bend changes,different detonation phenomena occurred along the wall of the bended pipe.If detonation wave propagating through bend with little curvature,the affection of the expansion wave is then stronger to induce the decouple process of the reaction zone and the leading shock.Re-setup of detonation can be completed when the overdriven detonation from another wall reignites the gas mixture in the decoupled zone,and then high overpressure impacts on the bend wall.

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Direct Simulation of a Uniformly Heated Film Flowing Down an Inclined Plate HU Jun, HU Guo-hui, SUN De-jun, YIN Xie-yuan 2004, 21(5): 415-420.  Abstract ( )   PDF (285KB) ( )   A Lagrangian finite element method is ued to simulate a uniformly heated film flowing down an inclined plate. An example with periodic inlet disturbances of different frequencies is computed,and the agreement with the linear stability theory shows that the Lagrangian finite element method has good resolution.The film flow is fully developed to saturated periodic wave,quasiperiodic wave,multipeaked wave and solitary hump.

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Direct Numerical Simulation Method of Inter-particle Collision CHEN Yin-mi, LIU Zhao-hui, ZHENG Chu-guang 2004, 21(5): 421-426.  Abstract ( )   PDF (354KB) ( )   A algorithm for direct numerical simulation of inter-particle collision in 3D space is built and verified by comparison with analytical solutions of collision rate of particulate flow under fine and heavy limits respectively. Optimizations such as exclusive method for computational mesh during identification of collisions can reduce the running time to 0.75% of that before optimization, without increscent relative error. It also shows that less time step can give more exact result in comparison of numerical simulations of the same particle group with different time steps. In precondition of no lost collision, fine computational mesh will save running time obviously.

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A Numerical Method for Solving Radiation Transport Equation on Lagrangian Mesh FENG Ting-gui 2004, 21(5): 427-431.  Abstract ( )   PDF (294KB) ( )   A numerically positive subcell balance method for solving radiative transfer equation on quadrilateral grids is presented.Numerical computation shows that the scheme presented is comparative to the discrete ordinate diamond scheme in rectangle grid computation,and that the present scheme is feasible in non-rectangle grid computation.

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The Application of Tikhonov Deconvolution Algorithm for Space Charge Distribution in Dielectrics HU Luo-quan, ZHENG Fei-hu, ZHANG Ye-wen 2004, 21(5): 432-438.  Abstract ( )   PDF (382KB) ( )   A numerical algorithm for space charge distribution in the planar dielectric sample by Pressure Wave Propagation (PWP)method is presented. The real space charge distribution is obtained from the deconvolution based on Tikhonov regularization method.Several technical treatments related to the deconvolution technique have been adopted,such as erasing the high frequency noise with wavelet packet filters,treating with integral equation using Tikhonov regularization method etc..The affect of noise for deconvolution algorithm is studied indetail by numerical experiments. It is shown that deconvolution algorithm for solving space charge distribution in dielectric can obtain very good results under low noise circumstance,however the numerical results are affected significantly under high noise circumstance,although they are still acceptable. There is evident smoothing effect for numerical solutions using regularization parameter α,but there is no significant effect for integral of numerical solution. Applying the deconvolution method to analyse experimental data,space charge distribution and electric field distribution are as well obtained successfully.

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Calculation of Quantum Chemistry for Mg-Si Based Thermoelectric Material JIANG Hong-yi, LIU Qiong-zhen, ZHANG Lian-meng, MIN Xin-min 2004, 21(5): 439-442.  Abstract ( )   PDF (225KB) ( )   Doping of moderate elements Sb,Te,Ag,Cu can greatly improve the thermoelectric properties of Mg2Si. For explaning the experimental result,a calculable model is presented.It applies DV-Xα quantum chemistry computation to reveal the micro-structure information, such as the covalent bond grade and the density of state. The calculated results imply that the covalent bond grade of Mg-Si are decreased and the forbidden gaps become narrower after doping. This results appears to be consistent with the experiments.

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Numerical Studies of Moving Shock Interacting with Consecutive Helium Bubbles CHEN Fei, ZHANG Meng-ping, XU Sheng-li 2004, 21(5): 443-448.  Abstract ( )   PDF (299KB) ( )   The numerical simulations is carried out on interface with large deformation induced by interaction between a moving shock and Helium bubbles.The high performance of the level set method coupling with GFM (ghost fluid method) method was demonstrated. Upwind TVD scheme was used to solve Eulerian equation for flowfield,and 5th WENO scheme was used to solve level set equation for fluid interfaces' tracking.GFM was applied to deal with the interface boundary.Example in Ref.[1] was used to validate our codes.Finally,the results were obtained on moving shock interacting with helium bubbles including the bubbles evolution.The results indicate that multi-interface can be perfectly tracked by extension of level set equation for multi-fluid interfaces.

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RfN Wavelets and Their Applications in Meteorological Data Analysis KUANG Zheng, ZHAO An-guo 2004, 21(5): 449-454.  Abstract ( )   PDF (310KB) ( )   A subclass of rational filter wavelets-RfN wavelets has been considered,and compared with DbN wavelets in theoretical and applied aspects.The conclusion that RfN wavelets is superior to DbN wavelets in these two aspects is drawn.The comparison about applications is conducted by analyzing meteorological data of Harbin region from 1881 to 2000.

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Parameter Sensitivity Analysis for the Satellite Thermal Design HAN Yu-ge, XUAN Yi-min 2004, 21(5): 455-460.  Abstract ( )   PDF (307KB) ( )   The parameter sensitivity analysis provides an evaluating method for the reliability validation of the satellite thermal design and the operating reliability of the satellite. In this paper the problem of satellite thermal design is analyzed and the sensitivity equations of the satellite thermal design are established by means of the theory of system sensitivity. As an example, the sensitivity equations have been applied to the parameter sensitivity analysis for the thermal design of the solar array of a satellite and the sensitivity of each design parameter has been also discussed. Such a procedure is necessary for the determination of physical and structural parameters in the satellite thermal design.

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An Analytical Method Utilizing Transfer Function for Coupled Heat and Moisture Transfer Processes in Walls XU Feng, SU Xiang-hui, ANG Hai-song 2004, 21(5): 461-466.  Abstract ( )   PDF (303KB) ( )   An analytical method by means of the transfer function is proposed to study the processes of coupled heat and moisture transfer in walls based on Luikov's equations.The calculations for coupled heat and moisture transfer in the fiberglass slab are conducted to obtain the transient distributions of temperature and 1-D distributions of moisture accumulation rate using the mentioned method. The results agree with the measured data, and show that the mathematical equations and the solving method are reasonable.

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A Calculation Model of Beam Envelope in LIA LI Xian-wen, WANG Wen-dou, DAI Zhi-yong, FENG Li, WANG Qiang, LI ping 2004, 21(5): 467-470.  Abstract ( )   PDF (205KB) ( )   A calculation model of accelerator beam envelope has been developed. It can predict beam envelope in linear induction accelerator from the injector to the final focus region. Its code can easily calculate the effect of various electric and magnetic element parameters on the beam. As calculating examples, the envelopes of 3 kA-beam current under the condition of 40 m long magnetic profiles are given.