Archive

25 November 2011, Volume 28 Issue 6 Previous Issue    Next Issue

---

For Selected:

Download Citations EndNote Ris BibTeX

Toggle Thumbnails

Select

Oblique Shock Wave Reflection in Condensed Matter CHEN Dawei, QIN Chengsen, WANG Pei, SUN Haiquan, YU Xijun 2011, 28(6): 791-796.  Abstract ( )   PDF (679KB) ( )   A study on oblique shock wave reflection in condensed matter is carried out by means of numerical simulation and theoretical analysis.Runge-Kutta control volume discontinuous finite element method is used to solve Euler equations.Equations of state for condensed matter adopt "stiffen gas" formulas.Patterns of oblique shock wave reflection in condensed matter are discussed.A shock polar theory is employed in analyzing critical agles of transition from regular reflection to irregular reflection.It gives states of reflected shock wave.Numerical results and shock polar solutions are compared and typical oblique shock wave reflections are obtained.

Select

Numerical Simulation of Seismic Coupling Effects in Underground Explosion with Different Explosion Modes XIAO Weiguo, WANG Xiaojun, LAO Jun, ZHU Haofeng 2011, 28(6): 797-802.  Abstract ( )   PDF (879KB) ( )   By using a numerical method developed in this paper,namely coupled Euler/Lagrange method,numerical simulations on seismic coupling effects induced by underground explosion with different explosion modes are carried out.Seismic coupling effects in tamped and cavity explosions in granite were studied.Dependence of decoupling factor on the initial cavity volume and the frequency were examined.It shows that the decoupling factor could reach 50 to 60 for completed cavity decoupling explosions in granite.

Select

Numerical Calculation of Multi-component Conservative Euler Equations Under Mie-Griineisen Equation of State WU Zongduo, ZONG Zhi 2011, 28(6): 803-809.  Abstract ( )   PDF (896KB) ( )   For multi-component fluid field under Mie-GrÜneisen equation of state,we consider some complex coefficients in Euler equations as conserved variables,and add new equations to simplify structure of original equation.In addition,mass fraction is introduced for different medium in field and flux is treated approximately.With modified Euler equation system and a MUSCL-TVD scheme we simulate interaction of different medium characterized by Mie-Graneisen equation of state.It shows that the approach makes the equations conserved and treats sharp interfaces with different medium well.

Select

Computation of Deformation and Instability of Low-density Bubble Induced by Incident and Reflected Shock Waves ZHU Yuejin, DONG Gang, LIU Yixin, FAN Baochun 2011, 28(6): 810-816.  Abstract ( )   PDF (1103KB) ( )   A three-dimensional simulation on deformation and instability of low-density spherical bubble induced by incident and reflected shock waves is performed with Navier-Stokes equations.A computational model validated by experiments is used to study deformation of bubbles,formation and three-dimensional instability of vortex rings.It is found that low.density spherical bubbles can deform and form vortex rings with different rotating directions along streamwise direction induced by incident and reflected shock waves. Baroclinic effect is the main reason for formation of vortex rings.Vortex rings move due to self-induced effect and flow field velocity. And azimuthal instability OCCURS due to disturbance.Finally.vortex rings may induce turbulent flow a8 they form a complicated structure dominated by small-scale streamwise vortices.

Select

Numerical Method for Relations Between Detonation Velocity and Curvature of High Explosives CHENG Junxia 2011, 28(6): 817-824.  Abstract ( )   PDF (344KB) ( )   We study relation of chemical energy and equation of state of plane detonation,and obtain the plane detonation shock equations and CJ eonditons.Detonation relations depending on curvature are gained with coordinate transformations of one-dimensional eylindrincal fluid dynamics equations.And at the same time we get a general sonic condition.Based on pressure and temperature equillibrium in reaction zone.we get relations between velocity of detonation and curvature of PBX9404 and PBX9502 as equations of state of products and reactants and reaction rates 8re known.As experiment data of explosive are known.tlIe method can be used to adjust parameters of equations of state and reaction rates.

Select

Domain Decomposition Algorithm witlI Multi-step Evaluation for Diffusion Equation SHENG Zhiming, CUI Xia, LIU Xingping 2011, 28(6): 825-830.  Abstract ( )   PDF (295KB) ( )   Domain decomposition parallel algorithms for one-and two-dimensional diffusion equations are studied by using multi-step evaluation revisions for interface points with fractional temporal index.Stability conditions are loose.In the algorithm,schemes with fractional step and large spacing discretization are used to evaluate interface points.The algorithms have same accuracy as full implicit method,while their stability bounds are released by q,the number of fractional step evaluations on interfaces between two neighboring temporal steps,times compared with existing algorithms.Convergence is proven rigorously with discrete maximum principle.Numerical experiments on parallel computers confirnl theoretical conclusions.They demonstrate looser stability conditions,good accuracy and parallel expansibility of the algorithms.

Select

Shear Flows in Resonant Surfaces During Nonlinear Evolution of Double Tearing Modes LI Xinxia, LU Xingqiang, GONG Xueyu 2011, 28(6): 831-834.  Abstract ( )   PDF (238KB) ( )   Shear flows in resonant surfaces of Tokamka devices induced by nonhnear evolution of double tearing modes(DTM) are studied numerically in the framework of resistive magnetohydronamic model with slab geometry.It is found that in early phases of nonlinear evolution of DTM,no remarkable shear flows is generated in resonant surfaces.Effective shear flows emerge during the phase of fast magnetic reconnection and disappear finally.Both amplitude and distribution of shear flows are found vary with nonlinear evolution of magnetic islands.Moreover,by taking into account plasma resistivity,it is shown that greater plasmas resistivity results in faster magnetic reeonection, but it hardly affects shear flows of resonant surfaces in Tokamka devices.

Select

Convergence Analysis of Newton-Laphson's Method for Coupled Magnetic and Flow Fields WANG Jinming, QU Shaobo, YU Bo 2011, 28(6): 835-842.  Abstract ( )   PDF (304KB) ( )   A local convergence condition of Newton-Laphson's method in solving diseretization nonlinear equation8 of coupled problems is shown and proved.It gives out relation among time-step and space.step and quasi.compres8ion factor. And it provides theoretically an assurance for convergence of Newton.Laphson's method within numerical analysis. Numerical example shows that the time-step in actual calculating can be greater than theoretical value 5lightly.

Select

Influences of Wall Topography on Unsteady Free Surface Waves in Film Flow PAK Myong-Il, HU Guohui 2011, 28(6): 843-852.  Abstract ( )   PDF (729KB) ( )   Two-dimensional unsteady failing film flows,with periodic perturbations at inlet。along a substrate with rectangular corrugations are studied numerically by using VOF method.It indicates that imposed periodic perturbations with different frequencies induce traveling surface waves with different wavelengths.As wavelength of structured wall is relatively short,it is found that the static deformed waves due to corrugations ride on the progressive wave resulted from imposed external perturbations.If these two wavelengths become close to each other.nonlinear effect promotes coalescence between neighboring surface waves.At a dimensionless film height 0.26,wavelength of wall equals to that of progressive wave at a perturbed frequency f=7 Hz,resonant phenomenon is observed in film flow.Additionally,we discuss effect of corrugations on structure of film flow field,and find that the phase velocity decreases as the trough depth of wall increased.

Select

Log-conformation-based Pressure-stabilized Fractional Step Algorithm for Viscoelastic Flows WANG Xuanping, LI Xikui 2011, 28(6): 853-860.  Abstract ( )   PDF (929KB) ( )   Based on log-conformation method developed recently,a log-conformation-based fractional step algorithm with stabilization mechanism is proposed by virtue of the finite increment calculus(FIC)process.The algorithm remarkably reduces computational cost within each iteration step compared with existed coupled solution schemes.Meanwhile it bypasses finite difference approximation for gradient of conformation tensor.As FIC process is introduced as pressure stabilization mechanism,restrictions on u-p interpolations imposed by LBB compatibility conditions are circumvented and equal-lower-order interpdlations for u-p are allowed to apply.Numerical simulations for cylinder flow show excellent stabilization and accuracy of the proposed algorithm.

Select

Displacement Performance of Visco-elasticity Polymer Flooding WANG Jing, LIU Huiqing, XU Jie, ZHANG Xiansong 2011, 28(6): 861-868.  Abstract ( )   PDF (943KB) ( )   A visco-elasticity polymer flooding mathematical model with three phases and five components is established with mass conservation principle.IMPES method is used to simulate the polymer flooding considering tackffying effect of elasticity,action of decreasing residual oil and visco-elasticity of heavy crude.It indicates that visco-elasticity polymer flooding decreases saturation of residual oil and increases viscosity of flooding system effectively,and then enhances oil recovery.As polymer concentration increases, oil recovery rises qucikly,and then tends stable.An optimal value is about 2 000mg·L-1.As injection rate grows.oil recovery increases and then declines.There exists an optimum value.Oil recovery increases rapidly with the increasing of injection volume,and then tends stable.The best volume is 0.6PV.

Select

Mathematical Model for Transient Flow of Non-Newtonian Heavy Oil with Dynamic Radius and Variable Viscosity LUO Yanyan, CHENG Linsong, HUANG Shijun 2011, 28(6): 869-874.  Abstract ( )   PDF (629KB) ( )   A mathematical model for transient flow of non-Newtonian heavy oil with dynamic radius and variable viscosity is established.The non-Newtonian transient pressure distribution of heavy oil is obtained with time and space.It shows that under same production,dynamic radius is closer to the well as threshold pressure gradient increases.The greater the threshold pressure gradient, the greater the pressure drop neflr the well.We combine dynamic radius and viscosity to avoid shortcomings of existing non-Newtonian heavy oil flow model.

Select

Rectification on Applicability of Mixed Point Process Decomposition YANG Ping, HOU Wei, FENG Guolin 2011, 28(6): 875-882.  Abstract ( )   PDF (1149KB) ( )   A mixed point process decomposition based on k-th nearest distance is introduced.Disadvantage in former researches is revealed and resovled.It is shown that the threshold of applicability judgment is not influenced as R is larger or smaller than critical value.Primary influences show as R is close to the theoretical calculation.Difference between theoretical and calculated R is analyzed. And numerical experiment is done.It is noticed that whether the critical value is revised or not,it depends on the number of point with almost a negative eorrelativity.In other words,the critical value is higher as sample size is small but is lower as sample size is large. As R lies in critical conditions.the inifialized valid value of k increases with increasing of sample size.

Select

Numerical Solution of Singular Source Problems with Barycentric Interpolation WANG Zhaoqing, QI Jiashuai, TANG Bingtao 2011, 28(6): 883-888.  Abstract ( )   PDF (676KB) ( )   Mathematical models for heat conduction with point source and beam bending with concentrated force include singular Delta function in the source term.Barycentric Lngrange interpolation is used to approximate unknown functions.Barycentric interpolation collocation method and barycentric interpolation Galerkin method for singular source problems are presented using relation between delta function and derivative of Heaviside function and integrated property of delta function.Formulations of the method are given in detail.Two one-dimensional examples and a two-dimensional example are shown.It demonstrates effectiveness and precision of the methods.

Select

Effects of Pulse Width on Ultrashort Pulse and Spectrum and Their CEP-dependence in a V-type Dense Medium LIANG Bian, LIU Zhongbo, JIA Kening, LIANG Ying, FAN Xijun 2011, 28(6): 889-894.  Abstract ( )   PDF (315KB) ( )   Effects of pulse width on ultrahort laser pulse and spectrum and their carrier-envelope phase(CEP)dependence in a dense V-type three-level atomic medium are investigated with numerical solutions of a full Maxwell-Bloch equation without slowly varying envelope and rotating wave approximations.It is shown that:As pulse width is small,pulse splitting number is less,spectrum is wide,high-frequency part of the spectrum is significant,CEP has great effect on pulse and spectrum,particularly effect on time interval between sub-pulses and strength of high-frequency part is more obvious;As pulse width increasing,pulse splitting number increases,width of spectrum narrows and high-frequency part of the spectrum decreases gradually,effect of CEP on pulse and spectrum weakens gradually.

Select

Statistics of Fermi Gas in a Strong Magnetic Field at High Temperatures with Quasi--classical Approximations MEN Fudian, HE Xiaogang, LIU Hui, ZHOU Yong, ZHOU Jiang 2011, 28(6): 895-900.  Abstract ( )   PDF (457KB) ( )   With quasi-classical approximations, statistic properties of Fermi gas in a strong magnetic field at high temperatures are studied. Analytical statistic characteristic quantities are given,and effects of magnetic field as well as temperature on statistic properties of the system are analyzed. Compared with a system in low temperatures.statiBtic characteristic quantities of Fermi gas in a strong magnetic field at high temperatures do not oscillate.The magnetic field deorease total energy of the system,and increases the chemical potential,heat capacity,entropy,pressure and stability of the system-The higher the temperature is,the weaker effects of magnetic field on total energy and heat caDacity and the stronger effects on chemical potential are.

Select

Model Investigation on Magnetic Field Molding of Strontium Ferrites QI Jingang, ZHAO Zuofu, ZHANG Dongjun, LI Feng, WANG Jianzhong, WANG Jun 2011, 28(6): 901-905.  Abstract ( )   PDF (821KB) ( )   Magnetic field molding is a key technique in obtaining hish-performance permanent magnetic materials from strontium ferrite,Based on a mathematical model,we focus on effect of domain center and material geometrical center's relative position on magnetic properties of strontium ferrite.It shows that the external magnetic field atcts on magnetic domain center more obviously as the center shifts downward;as the sample is flat and the external magnetic field vertically acts on the sample absolutely.the effect is the greatest,and strontium ferrite in shape anisotropy can be obtained.

Select

Quantitative Simulation and Density Reconstruction in High-energy X-ray Radiography XU Haibo, HU Yuan, WEI Suhua 2011, 28(6): 906-914.  Abstract ( )   PDF (635KB) ( )   Numerical radiograph using Monte Carlo method is used to study fidelity of density reconstruction in high. energy X-ray radiography.A density reconstruction method for a polyenergetic X-ray source and an object composed of different materials is proposed.The method includes energy spectrum,angular spectrum and spot size of photon source. And it indudes mass absorption coefficients explicitly in density reconstruction as well.A constrained conjugate gradient algorithm and variation regularization are applied to determine material edges and density reconstruction of a French test object.It shows that the method is valid for density reconstruction and energy spectrum of imaging photons is important in obtaining accurate material densities in high-energy X-ray radiography.

Select

Structure Evolution of Defects in BCC Iron by Dislacement Cascade:Molecular Dynamics Simulation CAI Jun, LU Daogang, MA Yan, YU Gang 2011, 28(6): 915-921.  Abstract ( )   PDF (567KB) ( )   Structure evolution and nature of defects in bcc iron by displacement cascade are investigated with molecular dynamics simulation.Under irradiation displacement cascade induces temporarily self-interstitials,vacancies,<100>, <110>, and <111> dumbbell defects,and composite defects as well,such as,composite defect of <110> and <111> dumbbell defects.composite defect of <110> and dumbbell defects,and defect clusters.Numerical results show that a higher PKA energy might induce more SIAs.The region where atoms are displaced by displacement cascade is about 11-15a0 in size.A smaller PKA energy gives rise to a smaller region of displacement cascade.At initial stage of 0-0-0.75 ps in displacement cascade,recombination of self-interstitial atoms and vacancies is found.

Select

Improved Shooting Method for Gross-Pitaevskii Equation: Interference of Three Bose-Einstein Condensates HUA Wei, LIU Xueshen 2011, 28(6): 922-926.  Abstract ( )   PDF (467KB) ( )   An improved shooting method is applied to 1D Gross-Pitaevskii equation,which describes Bose-Einstein condensate of neutral atoms in harmonic trapping potential at zero temperature.Eigenvalues of ground state of condensates with different nonlinear coefficient are given.Interference of three condensates after removing the trapping potential is studied with symplectie method.A periodic evolution is shown.Influence of relative phase on interference of condensates is discussed.

Select

Computing Stable and Unstable Manifolds of Typical Chaotic Maps LI Huimin, FAN Yangyu, ZHANG Jing 2011, 28(6): 927-932.  Abstract ( )   PDF (494KB) ( )   Homoclinie intemections are soul.ce of chaos for a map.It is convenient to determine whether a given map iS chaotic or not by computing stable and unstable manifolds of its hyperbolic fixed point and observing if there are homoclinic intersections.A new algorithm is presented to compute one-dimensional stable and unstable manifolds of a map.Inspired by a unique property that derivative is transported along the orbit of one-dimensional manifold.position of new point is located quickly with a two-step "prediction and correction" scheme.Tangent component of the manifold is used as reference line to check if the uew point is acceptable.Performance of the algorithm is demonstrated with several typical chaotic maps.It shows that the algorithm is capable of computing both one- dimensional stable and unstable manifolds of maps.

Select

Extreme Value Statistics of Growth Surfaces in (1+1)-dimensional Wolf-Villain Model WEN Rongji, TANG Gang, HAN Kui, XIA Hui, HAO Dapeng, XUN Zhipeng, CHEN Yuling 2011, 28(6): 933-941.  Abstract ( )   PDF (455KB) ( )   In order to study statistical properties of surface fluctuation in a Wolf-Villain(WV) model。maximal-and minimal-heigIlt distributions(MAHD and MIHD) of saturated surfaces in a(1+1)-dimensional WV model are investigated with theory of extreme value statistics.It shows that both MAHD and MIHD csn be fitted well with universal functions of different system sizes.They are asymmetrical.MAHD takes on a generalized Fisher-Tippett-Gumbel(FTG) distribution,a typical extreme value distribution function.MIHD,however,displays a slightly different distribution,a modified FTG distribution.

Select

Shape and Position of a Black Hole Shadow in SSD PAN Caijuan, MA You, ZHU Yunfeng 2011, 28(6): 942-948.  Abstract ( )   PDF (910KB) ( )   A rotating black hole is supposed to lie in a standard acc.retion disk.Imaging of the black hole shadow in an accretion disk are drawn as accretion disk inner boundary is equal to the last stable orbit.With qualitative and quantitative analysis of shape and position of a black hole,it is found that the size and shape of a black hole shadow for black holes with same mass are relevant to black hole spin.Shape and position of n rotating black hole shadow are asymmetrical relative to its rotating axis.The center of mass and rotation parameters of a black hole are determinated with position between rotating axis and black hole shadow.