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25 September 2011, Volume 28 Issue 5 Previous Issue    Next Issue

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A High-order Unstructured-grid WENO FVM for Compressible Flow Computation LEI Guodong, LI Wanai, Ren Yuxin 2011, 28(5): 633-640.  Abstract ( )   PDF (946KB) ( )   A general high-order unstructured-grid finite volume method based on least-square reconstruction and WENO limiter is presented.Some of the neighboring cells are employed to construct high-order polynomials.a least-square method is used tO solve overdetermined problem.The number of neighboring cells can be reduced with a general method,which saves memory and computing time. To achieve uniform accuracy and depress non-physical oscillation of conservation laws,a WENO limiter and rotated Riemann solver are employed.Two classical cases are provided to show resolution differences between high-order schemes and the second order scheme based on gradient reconstruction and Bath and Jesperson limiter.

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Extension of Kershaw Diffusion Scheme on Multi.block Grids ZENG Qinghong, PEI Wenbing, CHENG Juan, YONG Heng 2011, 28(5): 641-648.  Abstract ( )   PDF (522KB) ( )   Based on physical flux Kershaw scheme is extended to multi-block glids and algorithms for degenerative connection or strong connection unstructured points are shown.Flux continuity condition is met in the extended Kershaw scheme on multi-block girds which keeps energy conservation.Three numerical examples show good agreement with exact solutions. It validates accuracy and robustness of the extended Kershaw scheme on multi-block grids.

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Discontinuous Galerkin Method for Level Set Equation on Unstructured Grids LIU Shuaiqiang, OUYANG Jie, RUAN Chunlei 2011, 28(5): 649-658.  Abstract ( )   PDF (890KB) ( )   A new approach。a strong form of discontinuous Galerkin method(DGM),was developed to solve level set equation on unstructured drids.A weak form is only suitable for incompressible flow,while the strong form can used to solve level set equation in any case,including incompressible and compressible flows.Thc approach allows arbitrarib higlI order accuracy through Legendre-Gauss.Lobatto nodal distribution.Several numerical tests on one-,two-and three-dimensional unstructured grids demonstrate versatility and validity of the method.Besides,implementation ofthe strong form ofDGM brings benefits,such as high order,mars conservation, dimension independence,resolving interface location at the sub-cell level,handling complex domains,avoiding reinitialization and so on.

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K2_.SPH Method and Application for 2D Nonlinear Water Wave Simulation ZHENG Xing, DUAN Wenyang 2011, 28(5): 659-666.  Abstract ( )   PDF (475KB) ( )   Smoothed particle hydrodynamics is a Lagrangian meshless partilcle method.It gets superiority in simulation of free surface flow and large deformation problems. But low accuracy of kernel approximation becomes an obstacle for widely applications as particles are distributed disorderly or near a boundary.Adopting Taylor expansion and solving integral equation matrix.a second order kernel approximation method,namely K2_SPH is obtained and discussed.With improvement of kernel approximation,improved numedcal techniques are adopted.such as free surface boundary and solid boundary.They are very important for K2_SPH method.With comparison of standard SPH for nonlinear water wave simulation,K2_SPH improves obviously in free surface simulation and distribution of some variables in total particle system.

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An Implicit Re-initialization Method for Level Set Function Keeping Interface Fixed ZHANG Bin, LIU Xiaomin 2011, 28(5): 667-676.  Abstract ( )   PDF (508KB) ( )   To keep interface fixed.we derive formula of smoothing parameter in level set re-initialization equation and form a implicit re-initialization method.It was proved that as the developed method is used to reinitialize the level set function for ensuring sign of level set function on nodes near interlace the time step need only to satisfy the original CFL condition.Finally,the improved method is combined with the original method to make an accurate and fast implicit re-initialization method. Numerical examples illustrate effectiveness of the methods.

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Calculation of Water-droplet Impingement on Wing Surface SUN Zhiguo, ZHU Chunling 2011, 28(5): 677-685.  Abstract ( )   PDF (1204KB) ( )   We present systematic study on droplet trajectory calculation and impingement on wings.Fan-shaped partition and ceil topology methods ate applied to water droplet trajectory calculation.The droplet momentum equation is solved with fourth Runge-Kutta method.For a three-dimensional wing,position of droplet and velocity interpolation of collection efficiency on wing surface are discussed.Three discretization methods for control equation are used and compared.They are Euler method,predictor-corroctor,and Runge-Kutta method.Impingement of droplet is analyzed and droplet collection efficiency on a NACA0012 wing is presented.Effects of droplet diameter on collection efficiency are considered.A particle trajectory module DROP3D is integrated to ice accretion software. which gives droplet impingements and ice accretion on wing surface in different icing conditions.Accuracy and reliability of the code is verified.

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Rock Breaking Characteristics of Ultra-high Pressure Jet with Nozzle Combinations XU Yi, LIU Yongwang, XU Yiji, ZHANG Yuying 2011, 28(5): 686-692.  Abstract ( )   PDF (607KB) ( )   To maximize utilization of ultra high pressure jet energy,ultra high pressure jet flow field is studied with numerical simulation 0n different nozzle combinations.According to bottom flow field velocity vector and bottom hole pressure distribution,flow structure and drilling of nozzle combinations are analysed.A combination of three vertical edge nozzles has high efficiency on rock but is ineffective in cleaning the bottom and it results in wall erosion severely.Center plus a nozzle can clean the bottom and solve the problem of anti.wall erosion,but it requires greater high-pressure fluid displacement.Two vertical side nozzles and a center tilt nozzle or a vertical edge and a central nozzle combination is more favorable.A reasonable nozzle combination is essential in improving drilling efficiency.

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Productivity Calculation of Infill Horizontal Wells in Mixed Well Pattern YE Shuangjiang, JIANG Hanqiao, LI Junjian, HUANG Bo, SHI Chunmei 2011, 28(5): 693-697.  Abstract ( )   PDF (246KB) ( )   In productivity evaluation of infill horizontal well interference of oil or water wells are taken into account in a vertical and horizontal well mixed well pattern.With mirror-image method and source-sink theory,a semi-analytical model of productivity evaluation for infill horizontal well in random mixed pattern was built,in which interference of wells and pressure drop caused by wal friction and fluid acceleration were taken into account.It is suitable for infill horizontal well productivity calculation in arbitrary well pattern.

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Simulation of Trailing Edge Noise Based on Stochastic Noise Generation and Radiation Method CEHN Rongqian, WU Yizhao, XIA Jian 2011, 28(5): 698-704.  Abstract ( )   PDF (1079KB) ( )   Simulation of trailing edge noise based on stochastic noise generation and radiation(SNGR)method is shown.The SNGR method combines stochastic method with computational fluid dynamics,which gives acceptable noise result with relatively low computation cost.Reynolds averaged Navier-Stokes(BANS)equations arc solved by finite volume method.Acoustic perturbation equations are Bolved by finite difference method.Numerical scheme is a dispersion-relation-preserving(DRP)scheme.Non-reflection far.field boundary eonditions are utilized.A two.dimensional flat plate and an NACA0012 airfoil are simulated and compared with reference results.It is shown that the program predicts correctly trailing edge noise.

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Simulation of Gas-Solid Two-Phase Flow in a Bubbling Fluidized Bed with Variable.Scale Lattice Gas Automata LIN Liangcheng, ZHENG Zhong, ZHANG Jin, CHEN Wei, LI Dongyao 2011, 28(5): 705-712.  Abstract ( )   PDF (625KB) ( )   A variable-scale lattice gas automata model for gas-solid two-phase flow is established based on lattice gas automata (LGA)in which macroscopic behavior is described with microscopic gas-solid interactions.A two-dimensional flow field is divided into two.deck hexagon laRiees with different scales,where solid particles and gas pseudo-particles are aligned in lattices for solid and gas respectively.In addition to basic LGA rules.collision and propagation rules ale specifically designed for gas-solid systems,as well as additional evolution rules.A statistical method of macroscopic properties and conversion between model parameters and hydrodynamic properties based on similarity principle aIe established. Simulations of dynamic behaviors of gas-solid two-phase flow in a bubbling fluidized bed with this model show good agreement with experiments as well as simulation results with a two-fluid model.It has less average deviation,which validates the proposed model.

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Numerical Simulation of Cavity in Underground Pressure and Temperature Detonation WANG Tieliang, CAO Yuan, ZHANG Jianxin 2011, 28(5): 713-718.  Abstract ( )   PDF (299KB) ( )   A mathematical model is built for cavity temperature and pressure in underground detonation after the completion of cavity growth.It incorporates gas permeation in porous media,heat radiation between gas and cavity-wall and heat conduction between gas and ambient media.A corresponding one-dimensional code on the basis of spherical symmetry finite volume method is developed. Catty pressure and temperature of an underground nuclear test in alluvium at Nevada Test Site are computed.Measurment data of cavity pressure are analyzed in detail.

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Estimating Temperature-dependent Thermal Conductivity and Specific Heat Simultaneously ZHOU Yu, QIAN Weiqi, HE Kaifeng, GUI Yewei 2011, 28(5): 719-724.  Abstract ( )   PDF (492KB) ( )   Temperature-dependent thermal conductivity k(T)and specific heat C(T)are estimated simultaneously.At first,k(T) and C(T)are rewritten as functions of position and time,k(x,t)and C(x,t),and the gradient of cost function is deduced with adjoint equation method(AEM).Temperature is divided into segments and thermal conductivity and specific heat are expressed as constant in each segment.Gradients of cost function with respect to k(T)and C(<T)are further deduced from gradients of cost function with respect to k(x,t)and C(x,t).With a typical inversion problem,it is shown that the inversion method is feasible,effective and not too sensitive to measurement noise.

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BPT Algorithm for Weighting Ray Matrix in ART Algorithm XU Lingzhou, FAN Yiren, XIA Weifang 2011, 28(5): 725-729.  Abstract ( )   PDF (430KB) ( )   A weighting approach for ray matrix in ART algorithm for ultrasonic computerized tomogrnphy of concrete is developed. Firstly。a low-resolution image is generated by BPT algorithm and which is used asinitial value of iteration.Then,information of lowresolution image is used as weighting coefficients for ray matrix of ART algorithm.Image information and numerical information are used fully.High speed and low speed abnormal units can be weighted.As data error is less than 0.5%.examples show that the accuracy and iteration speed of improved method are better than that of traditional ART algorithm.

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Split-step Multisymplectic Integrator for Fourth-order Schrödinger Equation with Cubic Nonlinear Term KONG Linghua, CAO Ying, WANG Lan, WAN Long 2011, 28(5): 730-736.  Abstract ( )   PDF (315KB) ( )   A split--step muhisympleetic scheme is proposed for a kind of fourth-order Schrödinger equations with eubie nonlinear term.Ihe basic idea is to combine muhisymplectic integrator with split-step method.The method not only preserves muhisymplectic structure of multisympleetie integrators,but also has the virtue of efficiency and flexibility of split-step method in computation.Numerical experiments show that the split-step muhisympleetic method is more economic in computational time and computer memory than traditional muhisymplectic integrator.

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Numerical Study of 2-dimensional Time Dependent Schrödinger Equation ZHANG Chunli, CHEN Suhua, YANG Zhenyu, CHE Jixin 2011, 28(5): 737-742.  Abstract ( )   PDF (252KB) ( )   2-dimensional(2-D)asymptotic boundary condition(ABC) of 2-D time.dependent SchrOdinger equation (TDSE)for atoms in an arbitrary polarized laser field is investigated.The condition is obtained bv means of Fourier transformation,and the 2-D TDSE is discretized into a linear canonical equation solved via symplectic algorithm.An arbitrary polarized laser。atom interaction is also investigated.Calculated h讪order harmonic generation(HHG)spectra in good agreement with theoretical results.

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Runge-Kutta Method for Dynamical Equations of Polaron in PPV ZHAO Junqing, JIA Zhenfeng, ZHANG Tianyou, DING Meng, QIAO Shizhu, CHEN Ying, Ji Yanju, ZHANG Ningyu, FU Gang 2011, 28(5): 743-748.  Abstract ( )   PDF (465KB) ( )   An eighth-order Runge-Kutta(R-K)recurrence formula is constructed for differential equations.The formula i8 used tu simulate formation and movement of polarons in a one-dimensional poly-phenylenevinylene(PPV)molecular chain.The PPV chain composed of N carbons is described by an extended tight binding model.For N=160.the equations are solved by eighth.order R.K method.Stable polaron configuration and moving picture are obtained.Under electric field E=1×105V×cm-1.a poiaron moved along PPV chain at a velocity of 0.263 5Å·fs-1.It indicates that the eighth-order R-K formula is applicable to carrier movement in organic molecules.

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Computation of Defect Modes in a Photonic Crystal Slab Cavity HUANG Yonggang, FAN Heng, WANG Xuehua 2011, 28(5): 749-754.  Abstract ( )   PDF (869KB) ( )   Defect modes in a photonic crystal slab cavity are calculated with finite difference time domain method and group theory. Using symmetry boundary eondition.all frequencies of defect modes are obtained through dipole driving-sources with a broadband pulse.For one given frequency of defect mode,we use narrowband pulse to excite one single defect mode.Numerical results show that all defect modes with different symmetries can be obtained with this method.

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Partition Functions of Molecule SO2 WU Donglan, XIE Andong, WAN Huijun 2011, 28(5): 755-760.  Abstract ( )   PDF (324KB) ( )   Geometrical structures of32 S1602 and34 S16O2 are optimized at B3P86/cc-PV5Z level using Gaussian03 program. Equilibrium geometry。vibrational and rotational constants etc.are obtained.Total internal partition functions(TIPF)of32 S1602 and34 S16O2 are calculated from 70 to 6000K Witll product approximation.Rotational partition sums adopt WATSON rigidmtator model and vibrational partition sums use harmonie oscillator approximation.It is found that calculated results are consistent with those offered by HITRAN database.and errors show linear correlation approximately from 70 to 3000 K.By fitting errors,TIPF were corrected at high temperatures range from 3000 to 6000 K.Corrected values are fitted to a four-order polynomial of T.and coefficients are evaluated. This allows a rapid and accurate calculation of TIPF at 3 000-6 000 K.

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Five-order Analytical Potential Energies of Diatomic Molecular Ion XY+ in Energy Consistent Method for Ion LIU Guoyue, HAN Caixia 2011, 28(5): 761-766.  Abstract ( )   PDF (365KB) ( )   With energy consistent method for ion XY+(ECMI),three-order analytical potential energy function ECMI(3)for diatomic molecular ion XY+ is expanded to five-order ECMI(5)potential.ECMI(5)potential is used to study potential energy curves (PEC)of diatomic molecular ion XY+:B2Σ+ state of CO+ and b4Σ- state of SO+.It overcomes shortcoming of Morse potential or Huxley-Murrell-Sorbie(HMS)potential.1.hey are neutral diatomic molecular potential energy functions and can not be always correct for potential energy functions of diatomic molecular ion XY+.ECMI(5)potential shows excellently agreement with Rydberg-Klein-Bees(BKB)data.Higher-order ECMI potential generates reliable potential energy data in total area,including important asymptotic and dissociation regions where relative experimental data may be absence or quantum theoretical results may not be reliable.

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Molecular Dynamics Simulation of Energetic Deposition on Pt(111) Surface with Oblique Ni Atom Bombardment YAN Chao 2011, 28(5): 767-772.  Abstract ( )   PDF (740KB) ( )   Molecular dynamics simulation with embedded atom method is used to study energetic deposition on Pt(111)surface with Ni atoms at incident angles(θ)in a range of 0°to 80°(normal to the surface).Dependence of sputtering yields.adatom yields and vacancy yields on θ can be divided into throe different regions,θ≤20°,20°< θ < 60°,and θ≥60°respectively.As θ is smaller than 20°energetic deposition is similar to that at θ=0°.While 20° < θ < 60°,depth of projectile implantation decreases with incident angle.Distribution of adatoms is uniform,which contribute to uniformity of nucleation and layer-by.1ayer growth of film.As θ≥60°. energetic deposition has no obvious effect ou surface of Pt(111)substrate.

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Structure and Property of (K3N)n(n=1,…,5) Clusters: A Density Functional Study CHEN Yuhong, WANG Weichao, DU Rui, ZHANG Zhilong, ZHANG Cairong 2011, 28(5): 773-780.  Abstract ( )   PDF (365KB) ( )   Possible geometrical structures and relative stability of alkali metal nitride compound (K3N)n(n=1,…,5) clusters are studied with a hybrid density functional theory(B3LYP)with 6-311*-basis sets.Bond property,charge distribution,vibrational property and stabilities of the stablest isomers of (K3N)n(n=1,…,5)clusters are analyzed.It shows that the stablest isomers of (K3N)n(n=1,…,5) clusters are changing gradually from planar structure to three-dimensional structure.(K3N)4 and (K3N)5 are layered structure similar to crystal.Coordination rlnmhers of N atoms are usually 5 or 6.Natural charges of N atom and K atom are about-1.608e and+0.550e.respectively.A strong ionic bond exists between K atom and N atom.Dynamic stability of (K3N)4 cluster is higher than that of other clusters.

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Ab-initio Study on Elastic Properties of Single Wall Carbon Nanotubes ZHANG Liyun, GU Xuewen, SONG Rongli, ZHANG Na 2011, 28(5): 781-785.  Abstract ( )   PDF (284KB) ( )   Hartree-Fock and hybrid DFT and Hartree-Fock methods am used to calculate Young modulus of carbon nanotubos on the basis of ab-initio theory with program Crystal03.Calculated result with Hartree-Fock approximation agrees with other theoretical and experimental ones-Result with hybrid DFT and Hartree-Fock is smaller.Young's modulus of C nanotube depends on geometric structure and electronic structure as well.

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Thickness Dependence of Positive Exchange Bias in Ferromagnetic/Antiferromagnetic Bilayers XU Xiaoyong, GU Jiayin, MENG Runan, LI Tian, HU Jingguo 2011, 28(5): 786-790.  Abstract ( )   PDF (279KB) ( )   Cooling field dependence of exchange anisetropy Was investigated in ferromagnetic(FM)/antiferromagnetic(AFM) bilayers with antiferromngnetle interface coupling. It shows that the exchange bias HE Can change from negative to positive with increasing cooling field HCF and cooreivity HC acquires a maximum near crossover of HE.Especially.effect of FM and AFM thickness on exchange anisotropy is discussed in detail.Both negative(or positive)HE and HC always decrease with increasing of FM thickness tFM,which shows good agreement with experimental observation.It demonstrates interfacial nature of the exchange anisotropy.However,AFM thickness tAFM dependence of exchange anisotropy is relatively complex.In the case of positive HE,with increasing of tFM,HE increases and Hc decreases.But。in the valse of negative HE,HE decreases and HC increases with increasing tAFM.