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25 May 2014, Volume 31 Issue 3 Previous Issue    Next Issue

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Adsorption on Two-dimensional Boron and Carbon Based Nanostructures and Properties LIN Xianqing, CHEN Xi, NI Jun 2014, 31(3): 253-270.  Abstract ( )   PDF (8414KB) ( )   We review physical properties and potential applications of two-dimensional boron and carbon based nanostructures such as graphene and BC3 sheet adsorbed with metal atoms, non-metal atoms or molecules. Pristine graphene is semi-metallic with zero band gap, which is nonmagnetic and has weak spin orbit coupling (SOC). BC3 sheet is a semiconductor with an indirect band gap. As graphene and BC3 sheet are adsorbed with metal atoms, non-metal atoms or molecules, graphene systems may have a band gap at Dirac point, strong SOC, magnetic order and superconductivity. Applications in hydrogen storage may be realized in graphene and BC3 systems. In addition, it has been demonstrated that graphene can be used as gas sensors with significantly high precision.

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Runge-Kutta Control Volume Discontinuous Finite Element Method for Multi-medium Fluid Simulations ZHAO Guozhong, YU Xijun, LI Zhenzhen 2014, 31(3): 271-284.  Abstract ( )   PDF (4570KB) ( )   Runge-Kutta control volume (RKCV) discontinuous finite element method for multi-medium fluid simulations is constructed. Linear and nonlinear Riemann solvers are used for numerical flux at fluid interfaces. The method preserves local conservation and high-resolution. Numerical results show that even with a linear Riemann solver the schemes works well. Comparisons with Runge-Kutta discontinuous Galerkin method show advantages of RKCV method.

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Least Squares Isogeometric Analysis for Navier-Stokes Equations CHEN Dexiang, XU Zili, LIU Shi, FENG Yongxin 2014, 31(3): 285-291.  Abstract ( )   PDF (2763KB) ( )   With high order smooth non-uniform rational B-splines (NURBS) as basis function to simplify C1 element construction, least squares isogeometric analysis is proposed for viscous incompressible Navier-Stokes equations. Governing equations are linearized by Picard or Newton method. Variational equation is derived from least squares functional defined by residuals of linearized equations. High order smooth finite dimensional spaces for velocity and pressure approximation are constructed by NURBS. Two benchmark flow problems were solved. Accurate numerical results were obtained for 2-dimensional lid driven flows. Global mass loss in flow past a cylinder in a channel decreased from 6% in classical least squares finite element method to 0.018%. It shows that the method is applicable to Navier-Stokes equations. It is better in mass conservation than least squares finite element method.

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Algorithm Preserving Mass Fraction Maximum Principle for Multi-component Flows TANG Weijun, JIANG Lang, CHENG Junbo 2014, 31(3): 292-306.  Abstract ( )   PDF (5430KB) ( )   We propose a new method for compressible multi-component flows with Mie-Gruneisen equation of state based on mass fr action. The model preserves conservation law of mass, momentum and total energy for mixture flows. It also preserves conservation of mass of all single components. Moreover, it prevents pressure and velocity from jumping across interface that separate regions of different fluid components. Wave propagation method is used to discretize this quasi-conservation system. Modification of numerical method is adopted for conservative equation of mass fraction. This preserves the maximum principle of mass fraction. The wave propagation method which is not modified for conservation equations of flow components mass, cannot preserve the mass fraction in the interval[0,1]. Numerical results confirm validity of the method.

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Suitability of Low-order Numerical Schemes in Large Eddy Simulations LIU Tongxin, MA Baofeng 2014, 31(3): 307-313.  Abstract ( )   PDF (2222KB) ( )   Several low-order numerical schemes were evaluated for their suitability in large-eddy simulations based on 3D Taylor-Green vortex, with and without a subgrid-scale model. It shows that dissipation characteristics of three numerical schemes used are similar to a subgrid-scale model. At lower Reynolds numbers, flow fields are relatively smooth, numerical dissipation is lower; As Reynolds number increasing, transition to turbulence occurs and numerical dissipation grows greatly. For MUSCL and bounded centered schemes, subgrid-scale model has a little influence on results at high Reynolds numbers. The second-order central scheme exhibits lower dissipation, but at higher Reynolds numbers numerical dissipation still dominates total energy dissipation of flow. With an explicit subgrid-scale model the results even become worse. Therefore, for large eddy simulations in engineering, the second order central scheme is suitable, particularly without an explicit subgrid-scale model.

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Flow of Thin Film Containing Insoluble Surfactant over Grooving Topography Surface LI Chunxi, CHEN Pengqiang, YE Xuemin 2014, 31(3): 314-322.  Abstract ( )   PDF (3077KB) ( )   For flowing of thin film containing insoluble surfactant over grooving substrate, lubrication theory is adopted for evolution equations of liquid film thickness and interfacial surfactant concentration. Film flowing characteristics and the effects of related parameters are numerically simulated. It shows that as thin film of insoluble surfactant flowing over grooving topography, gravity and Marangoni stress driven by surfactant promotes flow of liquid film. Gravity plays a leading role since influence of surfactant is limited by fl ows of surface liquid and adjacent bulk liquid. Viscous force associated with topography has an opposite effect. Film deformation is weak as improving Bond number or reducing capillary number. Increasing groove depth or decreasing groove steepness encourages film deformation as improving Marangoni stress.

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A Semi-discrete Central-upwind Scheme for Multi-class Lighthill-Whitham-Richards Traffic Flow Model HU Yanmei, FENG Jianhu, CHEN Jianzhong 2014, 31(3): 323-330.  Abstract ( )   PDF (3024KB) ( )   A semi-discrete central-upwind scheme for multi-class Lighthill-Whitham-Richards (LWR) traffic flow model is presented. It combines improved fifth-order weighted essentially non-oscillatory (WENO) reconstruction called WENO-Z with semi-discrete central-upwind numerical flux. WENO-Z reconstruction improves accuracy of solution with non-oscillatory property. Time integration is carried out with strong stability preserving Runge-Kutta method. Numerical results demonstrate the scheme is efficient.

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Model of Porous Media with Settlement Distributed Porosity and Numerical Study YANG Wei, XUE Sihan, LIU Qinjian, ZHANG Shuguang 2014, 31(3): 331-334.  Abstract ( )   PDF (1031KB) ( )   Flow and heat transfer in porous media with settlement distributed porosity is studied. Based on ‘O-shape’ ring theory and in situ measurement, a distribution function of porosity in x direction is established. Considering change of fluid density, Brinkman-Forchheimer-extended Darcy model is introduced. Energy equation is solved with continuity boundary conditions. A model of flow and heat transfer in porous media with settlement distributed porosity is established. The model is discretized with difference method. Gauss-Seidel iteration method is used. Numerical analysis shows that:Fluid flow velocity in porous media with of settlement distributed porosity is greater near wall surface, and it is small at center. Increase of porosity near wall surface reduces low velocity zone and increases high velocity zone. As porosity is small, temperature decreases linearly. As porosity is large, temperature near high and low temperature wall surface reduces rapidly. The decrease becomes slower at center. Heat is transferred through conduction and convection together. Increase of porosity increases average Nusselt number and enhances heat convection.

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New Fast Multipole Hybrid Boundary Node Method for Thermal Analysis of 3D Composites MIAO Yu, SUN Tiancan, ZHENG Junjie 2014, 31(3): 335-342.  Abstract ( )   PDF (2498KB) ( )   Hybrid boundary node method (hybrid BNM) is applied for thermal analysis of 3D composites. A new formulation is derived for inclusion-based composites, which reduces degrees of freedom (DOFs) compared with conventional multi-domain solver. A version of fast multipole method (FMM) is coupled with new formulation for large scale analysis. Numerical examples are presented to analyze thermal behavior of composites with many inclusions.

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Analysis on Spectral Energy Distribution of Greenhouse Effect Under Global Warming Background GAO Fengling, CUI Guomin, TAO Leren, HUA Zezhao, HUANG Xiaohuang 2014, 31(3): 343-350.  Abstract ( )   PDF (1188KB) ( )   In a one-dimensional radiation transfer model, energy distribution and spectral absorption mechanism of greenhouse effect under Pre-Industrial and current atmospheric compositions were analyzed. Coupling mechanism between greenhouse effect and surface temperature was investigated on the basis of greenhouse gas concentrations at current level. It shows that warm environment before Industrial Revolution is mainly due to three strong absorption bands of greenhouse gases, which are (100-370)cm-1, (640-710)cm-1 and (1370-2000)cm-1 respectively. However, current global warming is originated from weak absorption bands of greenhouse gases, that is, radiation absorptions by (370-640)cm-1 and (710-1370)cm-1. Contributions to greenhouse effect increment of these weak bands after Industrial Revolution are 25% and 55% respectively. With rising temperature, contribution of right side of the earth's radiation peak wavenumber to total greenhouse effect shows positive change, while contribution of left side shows negative change.

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Primary Resonance Analysis of RLC Series Circuit with Nonlinear Capacitance LI Gaofeng 2014, 31(3): 351-356.  Abstract ( )   PDF (2085KB) ( )   For RLC series circuit with nonlinear capacitance, first approximate solution of primary resonance of nonlinear vibration system is obtained with method of multiple scales for nonlinear oscillations. Primary resonance responses of RLC series circuit show jump and hysteresis. With increasing of electromotive force primary resonance amplitude and resonant region increase. With increasing of resistance primary resonance amplitude and resonant region decrease.

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ab Initio Potential Energy Curves and Spectral Constants of SeOx(x=1,2) HAN Xiaoqin 2014, 31(3): 357-362.  Abstract ( )   PDF (1629KB) ( )   Possible ground state structures, harmonic frequency and dissociation energy of SeOx(x=1,2) free radical are optimized by different methods and base sets included in Gaussian 09. Among them, QCISD(T)/6-311+G(2df) and B3LYP/6-311G(3d2f) are the most suitable for SeO, SeO2. Calculation results are in good agreement with experiment. For SeO free radical, Murrell-Sorbie potential energy functional constant are calculated, according to which spectral parameters and force constants are shown. It provides basis for further investigation on SeOx(x=1,2). For SeO2 free radical, force constants are calculated at the same time. And potential energy functions of SeO2 are derived with many-body expansion theory. In a symmetric stretching vibration potential energy diagram of SeO2, saddle points in reaction kinetics O+SeO→SeO2 in the symmetry dilation potential energy are found. Activation energy is 48.24 kJ·mol-1. A stable SeO2 free radical could be formed as O atom with energy surpassing 0.5 eV.

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A Modified FDTD Scheme for Wave Propagation in General Cole-Cole Dispersive Media LIU Guangdong, ZHANG Kaiyin, FAN Shimin 2014, 31(3): 363-371.  Abstract ( )   PDF (2000KB) ( )   For finite-difference time-domain (FDTD) scheme in simulation of electromagnetic wave propagation in Cole-Cole dispersive media. Several improvements are made:(1) preserving a term with static ionic conductivity in Cole-Cole model, which is fit for real Cole-Cole media; (2) extending to three-dimensional (3-D) case; (3) selecting parameters of human breast tissues from experiment. Feasibility and validity of the scheme is preliminarily demonstrated by numerical examples. The modified scheme is propitious to wave propagation in general Cole-Cole dispersive media.

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Structure and Magnetic Properties of Co-doped (ZnO)12 Clusters XIE Jianming, CHEN Hongxia 2014, 31(3): 372-378.  Abstract ( )   PDF (3720KB) ( )   Structure and magnetic properties of (ZnO)12 clusters doped with one (monodoped) and two (bidoped) Co atoms are studied with first-principles method. Substitutional, exohedral, and endohedral doping are considered. Exohedral isomers are found the most favorable in both monodoped and bidoped clusters. Magnetic coupling between Co atoms is short-range. Magnetic coupling between Co atoms at the nearest neighbor is mainly governed by competition between direct Co-Co antiferromagnetic interaction and ferromagnetic interaction between two Co atoms via O atom due to strong p-d hybridization. We demonstrate that exohedral bidoped cluster favors ferromagnetic state, which has potential applications in nanoscale quantum devices.