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25 January 2006, Volume 23 Issue 1 Previous Issue    Next Issue

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Time Forced Collision Methods for Multiplication Rate Calculation WANG Rui-hong, DENG Li, XU Hai-yan, PEI Lu-cheng 2006, 23(1): 1-9.  Abstract ( )   PDF (280KB) ( )   In order to obtain more reaction information of neutron or the other secondary particles by forcing the collision to occur within a small time step, three Monte Carlo Time Forced Collision (TFC) sampling methods called discrete, large cross section and uniform time sampling method are presented, derived and tested. TFC method can be used in more complicated eases. For example, particle transporte through continuously changing materials within a cut time. Numerical results of simple multiplication system show that the calculation efficiency of TFC method is higher than that of the analog method by 2~4 magnitudes.

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A Linearized Differential Quadrature Method for Navier-Stokes Equations in the Streamfunction and Vorticity Form LI Chen, WU Xiong-hua 2006, 23(1): 10-18.  Abstract ( )   PDF (323KB) ( )   A new linearized differential quadrature method(LDQM) is applied to the unsteady Navier-Stokes equations in the stream-function and vorticity form. With LDQM nonlinear equations are solved easily. And the boundary conditions of ω can be expressed as a function of ψ. To verify the method, three examples are treated. Numerical results show that the method is of high accuracy and good convergence.

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A Calculation Method for Multimaterial Flows in a Unified Coordinate System Jia Peng-yan 2006, 23(1): 19-24.  Abstract ( )   PDF (232KB) ( )   A calculation method for muhimaterial flows in a unified coordinate system is shown. The node speed is determined with a moving mesh. Numerical results show good efficiency and accuracy of the method.

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A Muitisymplectic Fourier Pseudo-spectral Scheme for the SRLW Equation and Conservation Laws KONG Ling-hua, ZENG Wen-ping, LIU Ru-xun, KONG Ling-jian 2006, 23(1): 25-31.  Abstract ( )   PDF (259KB) ( )   A multisympletic system for the symmetric regularized long wave (SRLW) equation is obtained with canconical momentum. The system satisfies the multisymplectic conservation law. A Fourier pseudo-spectral method which adapts to periodic boundary conditions in space is introduced. An Euler mid-point scheme in time and a Fourier pseudo-spactral method in space are used to the muhisymplectic formulation of the SRLW equation. It makes a multisymplectic Fourier pseudo-spectral scheme. Several discrete conservation laws of this scheme are proved; Numerical experiments are performed to simulate the single soliton solution. The chase, collision and separation of multi-soliton solutions are simulated.

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Constructing a Class of Orthogonal-reinforced Hierarchical Hexahedra Vector FE LI Jiang-hai, SUN Qin 2006, 23(1): 32-36.  Abstract ( )   PDF (203KB) ( )   By the merits of hierarchial orthogonal polynomial, a method of constructing a class of orthogonal-reinforced hierarchical hexahedra vector finite elements(ORHHVFE) to achieve a better condition of systematic matrix is presented, and the basis functions of hierarchical hexahedra vector finite elements(HHVFE) at the angle of conforming elemental systematic matrices are studied in detail. Numerical tests of the ORHHVFE constructed using 1-st Legendre polynomials based on the above method and the other HHVFE were carried out and compared. The results show that the ORHHVFE has the same numerical precision with the HHVFE, and the conditions of systematic matrices by the ORHHVFE are improved largely.

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Improved Velocity Remapping Algorithms Based on SALE XIONG Jun, ZHOU Hai-bing, ZHANG Shu-dao 2006, 23(1): 37-42.  Abstract ( )   PDF (299KB) ( )   Based on the velocity remapping strategy of the SALE algorithm, three methods are proposed to improve the accuracy and monotonicity of momentum flux calculation on a 1D staggered grid: the SUR method which employs the upwind-type slope and a repairing procedure; the SM method which employs a minmod slope limiter; and the SLR method which employs a new slope limiter and a repairing procedure. These methods are second-ordered, conservative and bound-preserving. They inherit advantages of simplicity and high efficiency of the SALE algorithm. They are easily generalized to the two-dimensional case.

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A High-order Accurate RKDG Finite Element Method for One-dimensional Compressible Multicomponent Euler Equation CHEN Rong-san, YU Xi-jun 2006, 23(1): 43-49.  Abstract ( )   PDF (236KB) ( )   The RKDG finite element method, Level Set method and modified Ghost Fluid method with Isentropic fix are used to simulate a one-dimensional compressible multicomponent Euler equation. A third-order accurate RKDG finite element method is used to solve the Euler equation, the Level Set equation and the re-initiation equation. Numerical tests on one-dimensional compressible two-fluid flows are made and satisfactory results are obtained.

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A Parallel Nonlinear Conjugate Gradient Method with No-line-search WANG Jian, CHI Xue-bin, GU Tong-xiang, FENG Yang-de 2006, 23(1): 50-56.  Abstract ( )   PDF (215KB) ( )   A no-line-search parallel nonlinear conjugate gradient method(NLS-PNCG) for unconstrained optimization is proposed. In this method the step length is evaluated by a fixed formula. It is shown that the NLS-PNCG requires less computation and its performance is superior to those with line search on Deep Comp 6800.

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Numerical Simulations of a Falling Liquid Film on an Oscillating Inclined Plane HU Guo-hui, HU Jun, Yin Xie-yuan 2006, 23(1): 57-60.  Abstract ( )   PDF (175KB) ( )   The flow of a falling liquid film on an oscillating inclined plane is simulated numerically with Galerkin finite element method. The effects of oscillating frequency and initial perturbation frequency are investigated. A low-frequency modulation signal is observed in the flow field. Nonlinear effect of the low-frequency signal in the flow field promotes the coalescence of waves on a free surface, and accelerates the development of the waves. For higher oscillating frequencies, this effect is more apparent. A solitary hump is observed in the flow.

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A Primary Study of Transitions in Turbulence Models XIAO Zhi-xiang, CHEN Hai-xin, LI Qi-bing, FU Song 2006, 23(1): 61-65.  Abstract ( )   PDF (273KB) ( )   The Navier-Stokes equations are solved with the second-order LU-SGS-τTS implicit time-stepping method. The sixth-order symmetric TVD scheme with fifth-order WENO interpolation based on Roe is applied to the convection terms. A boundary layer flow around a flat plate, a low speed flow around the Aerospatial A-profile at high incidence and a transonic flow with shock/boundary interaction around RAE2822 airfoil are computed by Baldwin-Lomax and Spalart-Allmaras models with the transition criterion, respectively. The results show that the approaches capture the transition automatically.

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An Optimal Control Method for Aerodynamic Design of Airfoil with Multi-Constraint Conditions YANG Xu-dong, QIAO Zhi-de, ZHU Bing 2006, 23(1): 66-72.  Abstract ( )   PDF (267KB) ( )   Based on the optimal control theory and Navier-Stokes equations, aerodynamic design of airfoil with multi-constraint conditions, such as aerodynamic and geometric constraint conditions, is studied. According to a given problem, the corresponding adjoint equations, boundary conditions and final cost function formulation are derived in the computational space. In order to achieve the requirements of the numerical solution, final formulations in the physical space is also achieved. Numerical methods are developed effectively. By integrating the aspects, such as the flow analysis, the solution of adjoint equations, gradient solution, optimal arithmetic and grid generation etc., an aerodynamic design method involving drag reduction is successfully developed. Testing results show that the method has outstanding merits in the above aspects. It is effective and feasible for aerodynamic design with a large number of design variables. Computational time consumption is less than the conventional aerodynamic design method.

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A PDF Simulation of the Lifted Turbulent H2/N2 Jet Flame WANG Hai-feng, CHEN Yi-liang 2006, 23(1): 73-79.  Abstract ( )   PDF (251KB) ( )   A lifted turbulent H2/N2 jet flame in a hot and vitiated coflow is investigated numerically to explore the issues of autoignition as well as the flame lift-off. The composition probability density function (PDF) method is employed to facilitate the implementation of detailed chemical kinetics. A multiple-time-scale k-ε turbulence model is combined for the calculation of flow and turbulence fields. Detailed chemical reaction mechanisms of hydrogen oxidation are incorporated in the calculation. The predictions are compared with experimental data. The flame lift-off height and auto-ignition process are reproduced accurately by the model.

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A Calculation of Electron Hall Mobility in SiC WANG Ping, YANG Yin-tang, YANG Yan 2006, 23(1): 80-86.  Abstract ( )   PDF (282KB) ( )   With analysis of conduction band structure and isotropic relaxation time approximation, an analytical model for the electron Hall mobility and Hall scattering factor of n-type 6H-SiC is proposed. The impact of different scattering mechanisms on the low field electron transport in 6H-SiC is illustrated clearly. Three ellipsoidal and parabolic constant energy surfaces simplification are used. The calculated results are in good agreement with physical measurements.

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A Calculation Method of Sensitivity Distribution with Electrical Capacitance Tomography MOU Chang-hua, PENG Li-hui, YAO Dan-ya, ZHANG Bao-fen, Xiao De-yun 2006, 23(1): 87-92.  Abstract ( )   PDF (259KB) ( )   The relationship between the permittivity distribution and the measured capacitance in electrical capacitance tomography (ECT) is described by the sensitivity distribution which directly affects the image reconstruction. The sensitivity distribution is mainly computed according to its definition which is complicated and time-consuming. We analyze relationship between the sensitivity distribution and the electric potential distribution in ECT. The calculation formulae are pressented. The method is simple and fast. Simulation results show that the sensitivity distribution obtained by this method is consistent with that of the traditional method.

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A Numerical Study of Heat Transfer and Fluid Flow in a Periodically Wavy Channel XIE Gong-nan, WANG Qiu-wang, LUO Lai-qin 2006, 23(1): 93-97.  Abstract ( )   PDF (218KB) ( )   The periodically fully developed laminar heat transfer and fluid flow in a two-dimensional wavy channel in a compact heat exchanger are investigated numerically. Calculations are performed at Pr=0.7, in the range of Re=100~1100 with non-orthogonal non-staggered grids. The Semi-Implicit Method for Pressure Linked Equations Revised (SIMPLER) algorithm in the curvilinear body-fitted coordinates is used. The effect of the wavy height and distance on momentum and heat transfer is studied. Performance of model parameters is evaluated. It is shown that the overall Nusseh numbers and friction factors increase with the increase of Reynolds numbers. The friction factors and overall Nusseh numbers increase as increasing the wavy height or decreasing the wavy distance. The overall Nusseh numbers increase significantly with the wavy height, especially at high Reynolds numbers. The best wavy height and distance are 1.15 mm and 13 mm, respectively.

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Numerical Simulations for the DC I-V Curve of Superconducting Josephson Junctions ZHANG Jun-qin, YANG Yin-tang, HE Qing-li, LOU Li-fei, GUI Zhi-bin 2006, 23(1): 98-102.  Abstract ( )   PDF (183KB) ( )   Numerical calculations on Josephson junctions under microwave radiation are made by means of Runge-Kutta method in the RSJ model. The DC I-V curves of Josephson junctions reproduce experimental results very well.

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Treanor's and Gear's Methods in the Chemical Reaction Dynamics of NOx/SO2 Removal GONG Ye, ZHANG Jian-hong, WANG Xiao-dong, SUN Ji-zhong, LIU Yue, MA Teng-cai 2006, 23(1): 103-108.  Abstract ( )   PDF (219KB) ( )   Treanor's and Gear's methods are applied to chemical reactions in the process of NOx/SO2 removal. The results are satisfactory. The systems of NO-NO2-N2,NO-NO2-N2-O2 and NO-NO2-N2-O2-H2O are discussed. The removal of NOx and SO2 is also discussed as CO2 and SO2 are added.

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Numerical Analysis of Water Vapor Condensation During Unsteady Expansion in a Shock Tube WANG Mei-Li, LUO Xi-sheng, YANG Ji-ming 2006, 23(1): 109-114.  Abstract ( )   PDF (292KB) ( )   A numerical investigation is carried out for the phase change in the unsteady expansion of humid gases. The research is mainly focused on the process of water vapor non-equilibrium condensation in the presence of nitrogen and the influence of the condensation on the flow field in a shock tube. It is shown that the parameters of the flow field are disturbed and a condensation shock is generated due to the sudden release of the latent heat of condensation. With the condensation shock, the parameters and the structure of the flow field change dramatically.

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Approximate Normalization of Numeric Continuum State Wave Functions and Integral Processing of Residues in TRK Sums CAO Wei, ZHU Yun-xia, LU Hui, HE Li-ming 2006, 23(1): 115-119.  Abstract ( )   PDF (203KB) ( )   With an improved Numerov algorithm, continuum state wave functions and its normalization are investigated. Cowan' s normalization is discussed and a more precise and effective calculation is offered. We calculate the Thomas-Reiche-Kuhn(TRK) sum of several hydrogen atomic states (l=0~3). The least-squared method is used to generate infinite asymptotical forms of TRK. The residues are approximately calculated with an integral processing.

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Floquet Solution of Classical Motion Equation of a Neutral Particle in an Ioffe Trap LIU Xiao-liang, XU Hui 2006, 23(1): 120-126.  Abstract ( )   PDF (225KB) ( )   The motion of a neutral particle with magnetic moment,μ antiparallel to the field of an Ioffe trap is studied are obtained. With interaction between the magnetic moment of the particle and the magnetic field, classical motion equations of neutral particles in an Ioffe trap are abtained. With limited conditions we derive concise form of the motion equations using a perturbative method. They are Mathieu equations. With proper parameters the Mathieu equations are solved with traditional WKBJ method. As an attempt, we study periodic solutions, i.e., Floquet solutions of the Mathieu equation. It is necessary that parameters (λ and q) in the Mathieu equation satisfy special relations. With appropriate Ioffe trap parameters and initial condition of the particle, we present several periodic solutions.