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25 May 2010, Volume 27 Issue 3 Previous Issue    Next Issue

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A Lagrangian Finite Point Method for One-dimensional Compressible Multifluids with Tracking Interface Algorithm SUN Shunkai, SHEN Longjun, SHEN Zhijun 2010, 27(3): 317-325.  Abstract ( )   PDF (346KB) ( )   A Lagrangian finite point method for one-dimensional compressible multifluids is presented.The proposed method is a meshfree numerical procedure based on a combination of interior point scheme and interface point tracking algorithm.The discretization of unknown function and its derivatives are defined only by position of the so called Lagrangian points.The interior point formulation is based on Taylor series expansion in continuous regions on both sides of a interface.Unlike most current meshfree method,a point is settled at the interface position initially.State of interface point is updated using Rankine-Hugoniot conditions at interface together with characteristics difference computation.The interface tracking algorithm is the main feature of the method.Numerical tests show that the algorithm is oscillation-free at material interfaces and accuracy of the method is demonstrated.

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Subzonal Pressure Methods in Lagrangian Algorithm of Two-dimensional Three-temperature Radiation Hydrodynamics DAI Zihuan, WU Jiming, LIN Zhong, FU Shangwu 2010, 27(3): 326-334.  Abstract ( )   PDF (675KB) ( )   Computing methods for perturbation corner forces in electron pressure,ion pressure and photon pressure are investigated.We propose two kinds of subzonal pressure method for Lagrangian algorithm of two-dimensional three-temperature radiation hydrodynamics.Numerical tests show that both methods work well in eliminating unphysical deformation of Lagrangian mesh.

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Two Stencil Elimination Schemes with Preserved Symmetry in Finite Difference Approximation for Poisson Equations LI Houbiao, LIU Xingping, GU Tongxiang, HUANG Tingzhu, LI Hong 2010, 27(3): 335-341.  Abstract ( )   PDF (288KB) ( )   Two kinds of Stencil elimination schemes with preserved symmetry are presented.Correlative symmetric positive definite difference equations are obtained.Condition number of coefficient matrix decreases over 7/9 folding ratio than that of five point difference Jacobi's.Their eigenvalues have a good clustered spectrum.Theoretic analysis and numerical experiments show that they are better than un-symmetric ones,and are more useful.

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A Multi-moment Immersed-boundary Finite-volume Scheme ZHU Xiangde, CHEN Chungang, XIAO Feng 2010, 27(3): 342-352.  Abstract ( )   PDF (1097KB) ( )   A numerical model for incompressible flows in complex geometries is proposed by using multi-moment VSIAM3 scheme and immersed boundary method.Incompressible N-S equations are discretised by VSIAM3 scheme and complex and moving boundaries are treated with immersed boundary method.Immersed-boundary source terms in momentum equations are effectively represented by an extrapolated velocity field in ghost cells across the interface.Continuity equation is modified to take into account effective fluxes in boundary cells.With multi-moment VSIAM3 scheme uses local high-order reconstruction and collocated grids which are suited well for implementing immersed boundary method with high computational efficiency.The proposed scheme is verified by widely used benchmark test problems.Numerical results are fairly comparable to other existing methods.

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A Multi-material Arbitrary Lagrangian-Eulerian Method Based on MOF Interface Reconstruction JIA Zupeng 2010, 27(3): 353-360.  Abstract ( )   PDF (422KB) ( )   A multi-material arbitrary Lagrangian-Eulerian method is developed.Fluid equations are discretized by a compatible finite element method.A two-dimensional closure model for multi-material cells is presented.It is based on approximate Riemann solver HLLC and isentropic assumption.Interface in mixed cells is constructed by MOF methods.An accurate,conservative integration remapping method is used as mesh is rezoned.Example calculations are presented to show accuracy and robustness of the method.

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Dissipation Regulator for Central Fluxes in MHDs WU Hao 2010, 27(3): 361-368.  Abstract ( )   PDF (431KB) ( )   We propose a method to regulate numerical dissipation of central numerical fluxes in magnetohydrodynamics,and give a dissipation regulator for central numerical fluxes.We take Local Lax-Friedrichs flux as an example and apply the dissipation regulator in computation.A second order accurate MUSCL data reconstruction is used to extend Local LaxFriedrichs scheme to second-roder.Two test benchmark problems show that the dissipation regulator is effcient.

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Parallel Solution of Poisson's Equation on Irregular Domains CHEN Jun 2010, 27(3): 369-374.  Abstract ( )   PDF (376KB) ( )   We present a method for parallel solution of Poisson's equation on irregular domains,which is a key in solving threedimensional electromagnetic problem of a high power microwave device with complex geometry.Irregular domains are expressed with non-uniform grids,where neighbor grids can not be stored in neighbor positions,thus make parallelization difficultly.In our method,an irregular region is expressed by an uniform grid expression with geometry constraints,and then,a parallel Poisson equation is solved on irregular domains by using red-black reordering method.Numerical results validate effectiveness of the method.We also evaluate irregular domains'effect on parallel performance.

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Simulation of Unsteady Cavity Flow MA Xiaoliang, YANG Guowei 2010, 27(3): 375-380.  Abstract ( )   PDF (351KB) ( )   Menter SST based detached eddy simulations (DES) is performed for transonic flow over an open cavity to study unsteady flow and acoustic fields.Sound pressure level (SPL) spectra and overall sound pressure level(OASPL) on surface of the cavity floor and the cavity back wall are computed.It shows that the second mode is dominant with the largest magnitude in SPL.

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Simulation of Flows Around Two Tandem Rotating Cylinders in a Channel Using LB-DF/FD Method NIE Deming, GUO Xiaohui, LIN Jianzhong 2010, 27(3): 381-388.  Abstract ( )   PDF (514KB) ( )   An LB-DF/FD method,combined with lattice Boltzmann method (LBM) and direct-forcing/fictitious domain (DF/FD) scheme,is set up for fluid-solid interaction problems.The LB-DF/FD method uses two unrelated meshes to avoid re-meshing procedure.They are Eulerian mesh for the flow domain and Lagrangian mesh for the solid domain.LB-DF/FD method overcomes fluctuations in computation of forces on solid particle in conventional LBM.The method is validated with simulation of flow past a fixed circular cylinder,a circular cylinder moving in an infinite channel or rotating in an infinite field.Flow around two circular cylinders in tandem at low Reynolds numbers is simulated by using LB-DF/FD method.Effects of spacing gap between cylinders (g*) and Renolds number (Re) are investigated.Numerical results including streamlines,lift and drag force and torque exerted on the cylinder,at Re=0.001,0.1 and 10,0.2≤g*≤8.0 are presented.g* shows remarkable effect on lift and drag force and torque exerted on cylinders.Stokes cell number and drag force exerted on cylinders depend on Re.

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Lattice-Boltzmann Method for Gas Flow in Microchannels NIE Deming, GUO Xiaohui, LIN Jianzhong 2010, 27(3): 389-395.  Abstract ( )   PDF (333KB) ( )   A compressible lattice-Boltzmann model coupled with non-equilibrium extrapolation method are adopted to simulate gas flow in microchannels at slip regime (Kn≤0.1).Numerical results,including velocity profiles at outlet,pressure distributions and mass flowrates,agree well with analytical solutions and experimental results.In addition,gas flow in a 180 degree curved channel is numerically simulated.It shows that boundary layer separation is suppressed by slip velocity at the wall.In addition,mass flowrate of a curved channel is smaller than that of a straight one.

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Parameter Control in Temperature Analogy Method CHEN Yan, CAO Shuliang, LIANG Kaihong, ZHU Baoshan 2010, 27(3): 396-406.  Abstract ( )   PDF (1415KB) ( )   Parameter control are used to adjust grid quality in temperature analogy method.Movement of boundary is considered as temperature boundary condition.Energy equation or heat conduction equation is solved to get temperature distribution.In temperature analogy method,node's temperature is regarded as node's movement.By using different thermal conductivity and source term,different temperature distributions/node's movements are obtained to meet requirements.It shows that the method solves effectively dynamic grid puzzle in fluid-solid coupling.

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Mode Inverse Problem of Difference Discrete Models for a Beam with Overhangs WU Lei, LIU Quanjin, ZHANG Lihua, WANG Qishen 2010, 27(3): 407-412.  Abstract ( )   PDF (256KB) ( )   Mode inverse problem for a beam with overhangs is discussed.Flexural rigidity and density of beam with overhangs are solved with two groups of displacement modes or two groups of strain modes and corresponding frequency.Necessary and sufficient conditions for unique existence of solution of the problem are discussed.An algorithm is proposed and numerical calculations are carried out.Two examples show that better results can be attained if strain modes instead of displacement mode are employed.

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Numerical Inversion of Porosity LIU Fuping, CAO Yuezu, WANG Anling, YANG Changchun 2010, 27(3): 413-422.  Abstract ( )   PDF (525KB) ( )   Derivatives of well-bore and grid-block pressure to grid porosity are derived from initial boundary value problems of fluid equations in porous media and inner boundary condition.The derivatives are computed with numerical solution of 3D fluid equation in porous media.A inverse iterative equation is constructed by conjugate method.Numerical inversion of porosity distribution are realized for uniform or block uniform distribution reservoirs.It shows that the relative error of inverse porosity is less than three ten thousandths for a homogenous porosity reservoir with about 8-10 iterations.Relative error of inverse porosity is less than one thousandth for a block homogenous porosity reservoir.Computed porosity automatically approachs to the real value in a few iterations.

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Monte Carlo Study of Ti Film on Al Substrate Under High-intensity Pulsed Ion Beam Irradiation WU Di, WANG Jing, ZHANG Jianhong, GONG Ye 2010, 27(3): 423-427.  Abstract ( )   PDF (320KB) ( )   Monte Carlo method is used to simulate ions in a double-layer target of Ti film on Al substrate.As high-intensity pulsed ion beam (HIPIB) irradiates on target,deposited energy results in rapid increase of surface temperature.Meanwhile high energy ions make cross mixing among atoms at film and substrate interface.Shooting ions and energy deposition influence melting or vaporization of target materials.It changes adhesion between film and substrate.It shows that cascade collision mixing is not a main process in mixing of a double-layer target by HIPIB irradiation.The most preferable ion current densities lie in a range of 100 A·cm-2~150A·cm-2.

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Theoretical Study on Hydrogen Physisorption in Li-doped Single Walled Boron Nitride Nanotube Array CHENG Jinrong, FANG Xing, YUAN Xinghong, WANG Xiao, WANG Zhi 2010, 27(3): 428-432.  Abstract ( )   PDF (335KB) ( )   Hydrogen physisorption in Li-doped single-walled boron nitride nanotube array (SWBNNTA) is investigated in detail with grand canonical Monte Carlo simulations.It indicates that Li-doping is an effective mean to increase hydrogen storage capacity of SWBNNTA.The best doping scheme is studied.It shows that hydrogen storage capacity of Li-doped SWBNNTA at normal temperature and moderate pressure can exceed 2015 object of the U.S.Department of Energy.

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Fusion-Fission Hybrid Reactor in Energy Resource Strategy and Analysis for Hybrid Design LIU Chengan, SHI Xueming 2010, 27(3): 433-438.  Abstract ( )   PDF (309KB) ( )   Fusion-fission hybrid reactor in a long term energy resource strategy is described briefly.Capability of electricity and fissionable material production of a hybrid reactor consisted of typical fusion reactor core and blanket is analyzed emphatically.Capability of electricity production of composite fuel cycle system of hybrid and satellite reactors (e.g.PWR) is studied.Related calculations show that a natural uranium fueled and water cooled blanket is economical and less technical risk.

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Theoretical Study on Transverse Electronic Transport of Deoxyribonucleotides SU Wei, DONG Ruixin, LIU Hao 2010, 27(3): 439-445.  Abstract ( )   PDF (511KB) ( )   With density functional theory and non-equilibrium Green function method,we calculate I-V characteristics and transmission spectra of deoxyribonucleotides under low bias.Effect of electrode distance on transverse electronic transport is discussed.As distance between electrodes is less than 1.55 nm,it shows great influence on electronic structures.As the distance is more than 1.55 nm,the energy level near LUMO and HOMO changes slowly and the variation of LUMO-HOMO gap is very small.At a fixed distance between electrodes,the relative current of deoxynucleotides is not changed with lower biases (0.1~0.8 V).The current of T and C increases rapidly and is greater than that of A and G as the bias increases from 0.8 to 1.0 V.

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Variable Charge Molecular Dynamics Method in Canonical Ensemble MA Ying, XIE Guofeng, CHEN Shangda 2010, 27(3): 446-450.  Abstract ( )   PDF (291KB) ( )   A modified variable charge method based on iterative fluctuation charge model is proposed which is suitable for molecular dynamics simulation of a canonical ensemble.It compensates kinetic energy loss in simulation with thermal bath in the canonical ensemble.Molecular dynamics simulations show that this method has no energy leaking.Number of iteration in the modified method is reduced and the computational efficiency is increased.

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Hydrogen Molecular Ion Energy Levels in Superstrong External Parallel Magnetic Field with B-spline Technology HUI Ping 2010, 27(3): 451-456.  Abstract ( )   PDF (326KB) ( )   With interaction between atomic nucleus in a hydrogen molecular ion,one-center expansion method and B-splines basis technology are used to build radial wave function and angular wave function of a hydrogen molecular ion.Energy levels Eb (m=0,-1,-2,-3,-4,-5) and equilibrium internuclear separations 2R are calculated in superstrong external parallel magnetic fields.Strength of magnetic field changes from 2.35×106 T to 2.35×108 T.Compared with results by adiabatic variational approximation,the precision increases to a range between 0.00015 Ry and 0.0488 Ry;Compared with results by variational approximation,ours increases to a range between 0.0029 Ry and 0.0257 Ry.It shows that the duplicate B-splines basis function expansion method can get better completeness of wave functions and higher calculation precisions.

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Potential Energies of OH Ground State and the First Excited State HUANG Duohui, ZHANG Haiying, WANG Fanhou, ZHU Zhenghe 2010, 27(3): 457-462.  Abstract ( )   PDF (258KB) ( )   MRCI method with aug-cc-Pvtz,aug-cc-pVQZ,cc-pV5Z,6-311 ++ g(d,p) and 6-311 ++ g(3df,3pd) basis sets is used to calculate potential curves of OH ground state and the first excited state.Murrell-Sorbie potential functions are fitted.Force constants and spectroscopic data are obtained.Our results are in agreement with experimental values.

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A Method for Zero-order Term Elimination in Digital Holography CHAI Xiaodong, LI Xiaohui 2010, 27(3): 463-467.  Abstract ( )   PDF (436KB) ( )   By using independent component analysis,a suppression method for zero-order term is proposed in off-axis digital holography.At first,two different amplitude frames of holograms are captured by a CCD-camera to form an observation signal.Secondly,a twin-image and a zero-order term are separated by means of independent component analysis.Finally,a separated twinimage is subtracted remnants zero-order term,which eliminates the zero-order term effectively.Computer imitating experiments show that this method is better then actual phase-shift method on advantage and validity.

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Determination of Delay Time with Mutual Information by Equal-probability Symbolic Analysis Method LONG Haihui, ZHANG Dianzhong 2010, 27(3): 468-474.  Abstract ( )   PDF (437KB) ( )   An equal-probability symbolic analysis approach for mutual information function is proposed to improve routine symbolic analysis method.Firstly,the time series are rearranged according to the range from small to large.Then the rearranged time series are divided into several groups by equal-probability step and the number of groups are determined with empirical sub-formula.Finally,a critical point set of symbolic analysis method is made with boundary values of each group.Experiments of Lorenz and forced Brusselator show that this approach agrees well with Fraser' method while it is simplified significantly.