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25 July 2015, Volume 32 Issue 4 Previous Issue    Next Issue

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Artificial Viscosity Splitting Strategy in Lagrangian Algorithm for Two-dimensional Three-temperature Radiation Magnetohydrodynamics DAI Zihuan, WU Jiming, DING Ning 2015, 32(4): 379-385.  Abstract ( )   PDF (1569KB) ( )   An artificial viscosity splitting strategy for Lagrangian algorithm of two-dimensional three-temperature radiation magnetohydrodynamics is proposed to solves unphysical pinnacle problem in ion temperature around shock wave as edge viscosity and tensor viscosity are used. The strategy divides kinetic ernergy dissipated by artificial viscosity between electron interior energy and ion interior energy according to ratio of electron pressure and ion pressure. It is realized in two-dimensional three-temperature radiation magnetohydrodynamics code MARED and is used to simulate imploding process of Z-pinch. Unphysical pinnacle in ion temperature around shock wave is removed.

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A Distributed Parameter Contact Algorithm for Sliding Surfaces on a Three-dimensional Smoothed Contact Surface JIANG Yuxi, ZHOU Haibing, XIONG Jun, LIU Wentao 2015, 32(4): 386-394.  Abstract ( )   PDF (3136KB) ( )   In distributed parameter contact algorithm on three-dimensional contact surface,a method for smoothing three-dimensional contact surface is developed. In the method,a smooth contact surface is interpolated with bi-cubic parametric patches. A bi-cubic parametric patch is defined by using local information such as coordinates and normals of vertexes of patch. The smoothing technique provides an accurate representation of actual contact surface which is C1 continuous in patches and G1continuous(tangent plane continuous) between adjacent patches. Then C1 continuous smooth fields of normal pressure and density on smoothed surface are interpolated. And contact points on smoothed contact surface are calculated with Newton-Raphson iteration. Finally,contact constraints are computed with distributed parameter contact algorithm. Numerical examples demonstrate that smoothed contact surface alleviates‘chatter’of nodes and improves convergence behavior.

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Numerical Simulation on Chemical Nonequilibrium Flowfield in Standard Model LI Junhong, PAN Honglu, CHENG Xiaoli, SHEN Qing 2015, 32(4): 395-402.  Abstract ( )   PDF (3566KB) ( )   A three-dimensional computational fluid dynamics algorithm is developed to study chemical nonequilibrium flowfield in a standard model, ELECTRE, for which flight data exits. A finite rate chemistry model based on Dunn and Kang's model is implemented. An extensive investigation on catalysis modeling relevance simulations with non-catalytic wall conditions as well as with full catalytic boundary conditions is made. The method developed is used to compute detailed flow features of hypersonic flow around forebody of a sphere-cone vehicle under different attack angles and altitudes. It is shown that reacting gas numerical results are consistent with flight data. It shows that real gas effects are prominent in thin shock wave layers closing to the wall surface. It makes outstanding distance of shock wave short. Heat flux under full catalytic wall boundary condition is higher than that under non-catalytic condition. The greater the attack angle,the more obvious this variance and the less electron number density on the wall. The higher the flight altitude,the lower dissociation of oxygen and nitrogen,and the lower heat flux on stagnation point.

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Flow Topology Study on Shock-Flame Interaction ZHU Yuejin, DONG Gang 2015, 32(4): 403-409.  Abstract ( )   PDF (2635KB) ( )   To deeply understand mechanism of shock wave interacting with a flame,a numerical study on a planar incident shock wave and reflected wave interacting with a spherical flame was carried out with two-dimensional Navier-Stokes equations coupled with chemical reaction. Okubo-Weiss function are proved appropriate for compressible flow by analyzing characteristic equation of velocity gradient tensor. Emphasis was placed on two-dimensional flow topology characteristics of flame zone. It shows that integral of Okubo-Weiss function conserves within flame zone after passages of shock waves. However,inner and surface of flame zone display completely different flow status. Flow compressibility basically has no effect on evolution of flame. Besides,flow topology of flame zone is mainly controlled by foci and saddle,which means deformation is dominant in flow field.

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Numerical Analysis of Thermodynamics Models for Mars Entry Aeroheating Prediction MIAO Wenbo, LV Junming, CHENG Xiaoli, AI Bangcheng 2015, 32(4): 410-415.  Abstract ( )   PDF (2031KB) ( )   Numerical analysis is made to study thermodynamic models for surface thermal environment of Mars entering vehicles. It shows that flow in stagnation region stays almost in thermal equilibrium. As flight altitude rises,flow changes to thermal nonequilibrium. Heat transfer rate keeps the same in different thermodynamics models,if non-catalytic condition is set on the wall. In simulations with full-catalytic wall conditions,heat transfer rate in thermal non-equilibrium model become higher,due to difference of characteristic temperature in chemical reactions. The stronger the effect of thermal non-equilibrium is,the greater the characteristic temperature change and the heat transfer rate will be.

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A Transonic Aerodynamics Correction Method with Successive Kernel Expansion LIU Xiang, SUN Qin, WU Liang 2015, 32(4): 416-422.  Abstract ( )   PDF (1999KB) ( )   Most of current corrected panel methods failed to correct out-of-phase part of distributed unsteady pressure. A method combining traditional downwash weighting method and successive kernel expansion is developed. Precision of the method is verified with an example on ONERA M6 wing. Based on modified aerodynamics,flutter boundary of wing is calculated which predicts well nonlinear flutter of wing in transonic regime.

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A Lattice Boltzmann Model for Miscible Viscous Fingering in Porous Media JIN Xin, LIU Gaojie, GUO Zhaoli 2015, 32(4): 423-430.  Abstract ( )   PDF (2614KB) ( )   A lattice Boltzmann model for miscible viscous fingering in porous media is proposed. Stable displacement between two fluids with same viscosity is simulated. Good agreement with analytical solution is obtained. Specifically,effects of viscosity contrast and Peclet number are investigated. It shows that great viscosity contrast makes fingers grow faster. As viscosity contrast is given,there exists a critical Peclet number above which tip-splitting happens. Study on transversely averaged concentration profile indicates that mixing length first goes as t1/2,then shifts into a linear dependence in t.

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Performance Optimization and Analysis of Multi-physics Composition Program on JASMIN REN Jian, WU Linping, SHEN Weidong 2015, 32(4): 431-436.  Abstract ( )   PDF (1132KB) ( )   Invariable processor in a minimum federal algorithm is applied to RHSn2D program,which is a multi-physics composition program such as radiation hydrodynamics and particle transport based on parallel software infrastructure JASMIN. With improvement of parallel algorithm,RHSn2D program achieves parallel efficiency of 16% with 8192 processors for real models. Time analysis of integrated program demonstrates that perfermance of MPI collective communications in parallel software infrastructure decides computing time of radiation hydrodynamics with parallel algorithm.

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Stability of Liquid Droplet Containing Surfactant over Corrugated Topography Surface under Disjoining Pressure LI Chunxi, YANG Baocai, YE Xuemin 2015, 32(4): 437-448.  Abstract ( )   PDF (5786KB) ( )   For an insoluble surfactant-laden droplet spreading on corrugated topography,a disjoining pressure model induced by concentration of surfactant was established. Non-model stability theory was carried out to investigate stability of spreading. It indicates that compared with droplet spreading without disjoining pressure,under disjoining pressure advancing front height of droplet reduce apparently and spreading rate increases which improves stability of spreading. Long perturbation wave is conducive to enhance stability of droplet evolution and stability is enhanced with increasing wave number. However,spreading stability trends to deteriorate and even transit to unstable with increasing wave number of short perturbation waves. Reducing attraction strength coefficient α1 and increasing repulsion strength coefficient α2 promote spreading stability at small wave number(k=3). In addition,droplet displays more stable spreading with increasing α1 and decreasing α2 at large wave number(k=30).

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High-order Discontinuous Galerkin Time-Domain Finite-Element Method for Three-dimensional Cavities YE Zhenbao, ZHOU Haijing 2015, 32(4): 449-454.  Abstract ( )   PDF (1194KB) ( )   A high-order discontinuous Galerkin time-domain finite-element method based on Maxwell's curl equations is presented. It is a kind of domain decomposition method. Crank-Nicolson difference scheme is used for time-partial equation. Electric and magnetic fields are expanded using high-order vector basis functions with same order. Three-dimensional cavities are simulated to demonstrate accuracy and efficiency of the method. It shows that time step size is no longer restricted by Courant-Friedrich-Levy(CFL) condition.High-order vector basis function could improve accuracy compared with Whitney 1-form vector basis function.

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Three-Dimensional Time-Domain Electromagnetic Inverse Scattering Technique for Debye Dispersive Media LIU Guangdong, YU Guangqun, FAN Shimin 2015, 32(4): 455-468.  Abstract ( )   PDF (4687KB) ( )   Dielectric properties of a variety of media,such as biological tissues,soil,and water,are frequency-dependent,which are depicted frequently by a single-pole Debye model. A three-dimensional (3-D) time-domain electromagnetic inverse scattering technique,based on functional analysis and variation method,is developed to reconstruct dispersive properties of media. Main procedures of the technique are: ① Inverse scattering problem is turned into a constrained minimization problem,according to the least squares criterion; ② Resulting problem is translated into an unconstrained minimization one,using a penalty function method;③ Closed Fréchet derivatives of Lagrange function with respect to properties are derived,based on calculus of variations; ④ Resulting problem is solved with any gradient-based algorithm. Furthermore,a first-order Tikhonov's regularization is adopted to cope with noise and ill-posedness of the problem. In numerical experiment,the technique is applied to a simple 3-D cancerous breast model,with Polak-Ribière-Polyak conjugate gradient algorithm and finite-difference time-domain method. Simulated results demonstrate preliminarily feasibility,effectiveness and robustness of the method.

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Calculation of Oil-Gas Contact Migration Distance in Gas Cap Reservoir ZHANG Angang, FAN Zifei, SONG Heng 2015, 32(4): 469-474.  Abstract ( )   PDF (964KB) ( )   For gas cap reservoir with strata dip,mechanical property of oil-gas contact movement is described by particle-tracing of Lagrange. With assumption of straight line movement,movement of oil-gas contact is obtained by basic differential equations of oil and gas seepage. Application results show that: With decrease of reservoir pressure,decline of gas phase potential is much greater than oil phase potential; Oil-gas contact intends to move towards oil well as oil rim is only developed; On the contrary,oil-gas contact intends to move towards gas well as gas cap is only developed; Rational control of oil recovery rate and gas recovery rate is beneficial to stabilize oil-gas contact.

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Parallel Algorithms for Separable Elliptic Equation based on GPU CAO Jianwei, XU Xiang, WANG Younian 2015, 32(4): 475-481.  Abstract ( )   PDF (1324KB) ( )   We study parallel algorithms of Jacobi iteration and DRM based on GPU for separable elliptic equation. Two test cases are performed on GTX 570 platform to verify validity of parallel algorithms. It shows that the maximum speed-up ratio on DOUBLE reaches about 14. And efficiency reaches 53% for Jacobi iteration. Besides,the maximum speed-up ratio on DOUBLE reaches about 3.8. And efficiency reaches 15% for DRM algorithm.

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Electronic Mechanism of Dislocation and Doping for Impact Toughness of Ductile Cast Iron YANG Zhonghua, LIU Guili, QU Yingdong, LI Rongde 2015, 32(4): 482-486.  Abstract ( )   PDF (1101KB) ( )   Atom module of α-Fe [100](010) edge dislocation is built in metallic matrix of ductile cast iron. Density functional theory CASTEP method is employed to calculate energy parameters of carbon doping edge dislocation system including atom embedded energy,affinity energy and Mulliken population. It shows that there exist C2v symmetry group in structure of α-Fe [100](010) edge dislocation and localized effect of dislocation happens in limited range. Energy valley attracts light impurity carbon which forms atom clusters in dislocation corn. Interaction between C and Fe atoms is strengthened with charge transportation between C-4s and Fe-2p obtains which pins dislocation slipping. Mulliken population of Fe atom and C atom is high. Length is short. Iron carbide could be produced. Binding energy and PDOS of carbon doping cementite system show that silicon promotes cementite decomposing and nicalon becomes corn of graphite ball,which improve impact toughness of ductile cast iron.

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BaTiO3/SrTiO3(1:1) Superlattice WANG Jiangduo, DAI Jianqing, NIU Zhihui, ZHANG Hu, SONG Yumin 2015, 32(4): 487-495.  Abstract ( )   PDF (981KB) ( )   Lattice dynamics,electronic and lattice contributions to dielectric and piezoelectric responses of BaTiO3/SrTiO3(1:1)(BTO/STO 1:1) 10-atom superlattice with Ba/Sr [110] and [111] ordering were investigated with first-principles calculations. We explored ground structure from the highest phase by successively freezing in unstable polar modes. We found that ground structure are in Pm and R3m symmetry,respectively. Lattice contributions to dielectric and piezoelectric tensor coming from individual atoms and individual modes were explored. O and Ti atoms provide extraordinary great contribution to lattice dielectric and piezoelectric responses. On the other hand,great dielectric and piezoelectric tensor are mainly due to low frequency phonons. Especially,for BTO/STO(1:1)superlattice with Ba/Sr [110] ordering,ε11is mainly due to A' phonons with ωλ=49 cm-1.

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Analysis and Implementation of a Simplest Charge-controlled Memristor Chaotic Circuit TAN Zhiping, YANG Hongjiao, LIU Qineng, ZENG Yicheng 2015, 32(4): 496-504.  Abstract ( )   PDF (3258KB) ( )   A simplest cascade memristor chaotic circuit is constructed with a charge-controlled memristor,an inductance,a capacitance and a negative conductance. Dynamic properties of the circuit are demonstrated by means of equilibrium stability,Lyapunov exponent spectra and bifurcation diagrams. Numerical simulation shows that a class of particular single scroll chaotic attractors is produced in the case of one equilibrium point. With increase of system parameter,the circuit exhibits complicated chaotic behaviors. Pspice simulations are well consistent with theoretical analysis and numerical simulation.