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25 January 2014, Volume 31 Issue 1 Previous Issue    Next Issue

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A RKDG Finite Element Method for Lagrangian Euler Equations in One Dimension LI Zhenzhen, YU Xijun, Zhao Guozhong, Feng Tao 2014, 31(1): 1-10.  Abstract ( )   PDF (1958KB) ( )   We present a Lagrangian scheme for one-dimensional Euler equations.The scheme uses Runge-Kutta discontinuous Galerkin (RKDG) finite element method to solve Euler equations under Lagrangian framework.The mesh moves with fluid flow.The scheme is conservative for density,momentum and total energy.It achieves second-order accuracy both in space and time.Numerical tests are presented to demonstrate accuracy and non-oscillatory properties of the scheme.

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A Reduced-Order Simulation Model for Parabolized Navier-Stokes Equations LUO Yuou, YU Yan, LUO Zhendong 2014, 31(1): 11-20.  Abstract ( )   PDF (1509KB) ( )   With proper orthogonal decomposition (POD) technique and singular value decomposition method we establish a reducedorder simulation model for parbolized Navier-Stokes equations.Stability and errors of solutions are discussed.Choice and update of POD basic are instructed by means of error estimates.Numerical experiments are presented to illustrate validity and feasibility of the model for parbolized Navier-Stokes equations.

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A Corrected Panel Method for Static Aeroelasticity JIA Huan, SUN Qin, LIU Jie 2014, 31(1): 21-26.  Abstract ( )   PDF (2786KB) ( )   A corrected panel method is shown and applied to static aeroealsticity.Based on CFD data at different attack angles the method approximates curved lifting lines by linear segment.The corrected panel method fills drawback of original one by considering nonlinear factor.Compared with CFD,similar accuracy limit and higher efficiency are obtained in aerodynamic force loss and attack angle compensation of M6 wing.It indicates that the method is suitable for complex structure optimization.

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SPH for Developing Supercavity Induced by High Speed Underwater Body ZHENG Jun, YU Kaiping, WANG Junfeng, LI Changfeng 2014, 31(1): 27-32.  Abstract ( )   PDF (1755KB) ( )   Smoothed particle hydrodynamics (SPH) is tested for simulating flow driven by high speed underwater body (FDUB).Developing history of supercavity induced by a body is predicated by SPH.Shape of developed supercavity derived by SPH is compared with result given by principle of independence of cavity sections expansion of Logvinovich.Ghost particle method and Dummy particle method,that remedy boundary deficiency of SPH,are combined to implement wall conditions.

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Numerical Study of Chemical Nonequilibrium Effect on Aeroheating Environment of Hypersonic Vehicles ZHANG Shengtao, CHEN Fang, LIU Hong 2014, 31(1): 33-43.  Abstract ( )   PDF (3489KB) ( )   Chemical nonequilibrium effect on aeroheating environment of hypersonic vehicles is numerically investigated.First,three gas models are considered for comparing chemical nonequilibrium effect on aerodynamic and aeroheating characteristics over a 2D cylinder-blunt body.Then,a 3D sphere-blunt body is taken to further investigate chemical nonequilibrium effect,especially wall catalysis effect on aeroheating environment.It indicates that chemical nonequilibrium effect does not affect pressure significantly,but reduces shock-standoff distance remarkably and, more importantly, post-shock temperature, and hence affects aeroheating environment significantly.Moreover,wall catalysis effect affects aeroheating environment significantly,and thus effective control of this process reduces wall heat transfer considerably.It is concluded that understanding and accurate prediction of chemical nonequilibrium effect are of decisive importance for the design of thermal protection systems (TPS) of hypersonic vehicles.

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Maximal Penetration Depth of Micro-jet from Void Under Shock Loading LIU Chao, FENG Qijing, QIN Chengsen, LIANG Xianhong 2014, 31(1): 44-50.  Abstract ( )   PDF (2836KB) ( )   A two-dimensional elastic plastic hydrodynamics Eulerian code MEPH is applied to simulate micro-jet formation and penetration process of void in sample during shock loading.We focused on forming process of micro-jet.Maximal penetration depth versus key factors such as shock pressure and void diameter is analysed.Theoretical jet penetration is compared with numerical simulations of maximal penertration depth.

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Shock Induced α-Iron Phase Transition in DEM LIU Chao, SHI Yina, QIN Chengsen, LIANG Xianhong 2014, 31(1): 51-58.  Abstract ( )   PDF (2828KB) ( )   Discrete element method combined with undiffused two-phase transition model,thermodynamic consistent Helmholtz free energy function,and phase transition kinetics of relaxation equation are used to simulate α-iron phase transition process.Through simulation of phase boundary,Hugoniot relation and free surface velocity profiles are obtained.Wave interaction in loading and unloading process under different pressures is analyzed.Characteristics of loading and unloading wave velocity are acquired.

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Numerical Analysis of Heat and Mass Transfer During Pyrolysis of Coal Particle LIU Xunliang, CAO Huan, WANG Gan, WEN Zhi 2014, 31(1): 59-66.  Abstract ( )   PDF (2350KB) ( )   A mathematical model is developed to analyze numerically coal pyrolysis and heat transfer inside a heated coal particle.Endothermic effect of decomposition and transpirational convective heat transfer are taken into account.A coupled comprehensive model was validated with experimental data of pulverized coal and large particles.Then,temperature history and coal pyrolysis of coal particle heated were analyzed numerically.Effects of endothermic of pyrolysis,transpirational convection,volatile content and particle size were investigated to understand physically transient temperature and volatile evolution of coal particle.

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An Algorithm for Multi-physics Field Reconstruction Based on Molecular Relaxation Model of Mixtures LIU Yan, LIU Shi, LEI Jing, Schlaberg H I 2014, 31(1): 67-74.  Abstract ( )   PDF (2823KB) ( )   We investigate relaxation absorption of ultrasound and speed of sound dependence on temperature and constituent concentration of gas mixture.Two three-dimensional models,one based on molecular relaxation model and the other on sound velocity, are established for a sample consisting of carbon monoxide, nitrogen and oxygen.An algorithm is developed to reconstruct simultaneously temperature field,concentration field and flow of the mixture in sensing domain.Numerical simulation shows that the algorithm is feasible and applicable to measurement of complicated multi-physics fields.Errors arising in simulation are discussed.It is possible to use the algorithm for other component mixtures.

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Support Vector Machine and Neural Network in Inversion of Rough Surface Parameters GOU Xueyin, GUO Lixin, ZHANG Lianbo 2014, 31(1): 75-84.  Abstract ( )   PDF (3891KB) ( )   Support vector machine and neural network theory and internal network training differences of them are studied.Root mean square height and correlation length of Gauss rough surface are inversed by support vector machine and neural network,respectively.Simulation results and inversing errors show that in the case of small numbers of rough surface sample inversion of support vector machine are better than that of neural network,while in the case of sufficient numbers of rough surface samples inversion accuracy of neural network increases and time of inversion by neural network is much less than that of support vector machine.

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Influence of Lattice Constant on Transmission,Negative Refractive Index and FOM of Left-Handed Materials ZHONG Min, YE Yonghong 2014, 31(1): 85-90.  Abstract ( )   PDF (2212KB) ( )   Influence of lattice constant on transmission,negative refractive index (NRI) and FOM of left-handed materials was studied.It shows that lower-order transmission peak of left-handed materials increases unusually with lattice constant decreased,due to impedance matching.And center frequency of NRI of left-handed materials is blue-shifted with decreased lattice constant,which is consistent with theoretical results.As lattice constant decreased to a certain value,perfect impedance matching is achieved which leads to higher FOM.

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Finite Difference Time-domain Method Based on High Order Compact Scheme KUANG Xiaojing, WANG Daoping, ZHANG Liang, WU Xianliang, SHEN Jing, KONG Meng 2014, 31(1): 91-95.  Abstract ( )   PDF (1729KB) ( )   A high efficiency finite difference time-domain method based on high order compact scheme is shown.It not only improves accuracy,but also has the advantages of fewer grid nodes,lower memory consumes and CPU time.Numerical simulations of electromagnetic wave propagation in a lossless waveguide and photonic crystals fibers are realized.They prove efficiency and accuracy of the algorithm.

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Electronic and Magnetic Properties of F Atoms Adsorbed TiO2:Mn(001) Diluted Magnetic Semiconductor Thin Films:First-principles Calculation LI Xiangran, LI Dan, WANG Chunlei, NIU Yuan, ZHAO Hongmin, LIANG Chunjun 2014, 31(1): 96-102.  Abstract ( )   PDF (1808KB) ( )   We performed first-principles calculations of Mn-doped structures in which Mn atoms substitute Ti atoms.Formation energy,density of state and magnetic moment are calculated for Mn ions doped TiO2(001) and F-TiO2(001) thin films.In all doping configurations adsorption of F atoms on surface lowers formation energy of TiO2:Mn system significantly.Magnetic moments of Mn ions are reduced,whereas those of O atoms on surface are increased.Magnetic moment of O atoms is mainly derived from spin polarization px and py orbitals.F adsorption promotes doping of Mn atoms and improves stability of structure,magnetism,and metallicity to a certain extent.

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Analytical Model and Performance of Optimized Dual-channel 4H-SiC MESFETs YOU Na, ZHANG Xianjun 2014, 31(1): 103-108.  Abstract ( )   PDF (1745KB) ( )   Dual-channel 4H-SiC MESFET is optimized for high power microwave applications.Physics-based analytical models for the device are obtained by solving one- and two-dimensional Poisson's equations.Direct-current (DC) and alternating-current (AC) performances of the 4H-SiC MESFET are calculated.The result is in agreement with experimental data.Calculated maximum saturation current density and breakdown voltage are about 420 μA·μm-1 and 155 V,respectively,which are greater than those of dual-channel structure,275 μA·μm-1 and 141 V.Resultant maximum output power density is 7.4 W·mm-1,which is 64% higher than that of dual-channel structure.Cutoff frequency and the maximum oscillation frequency are slightly improved.The power performance is significantly improved while its AC characteristics are not degraded.

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An Interconnect Energy Distribution Model Based on Non-uniform Wire-size ZHANG Yan, DONG Gang, YANG Yintang, LI Yuejin 2014, 31(1): 109-114.  Abstract ( )   PDF (766KB) ( )   Based on interconnection transmission differential equation,transform voltage and current expressions are derived by incorporating appropriate boundary conditions for interconnect energy analysis.We considered a practical transmission line with driver and load to find out relation between transform input and output voltage and current responses.Interconnection energy distribution is obtained,which considers non-ideal step stimulation.In 65 nm CMOS process,the non-uniform interconnect analytic model enables to estimate energy within 5% compared with Hspice simulations.The method has high accuracy.The analytic model can be applied to front end optimizing design and analysis of high performance global interconnection.

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Potential Energy Functions of BH Molecule in External Electric Fields WU Donglan, TU Juan, WAN Huijun, ZENG Xuefeng, XIE Andong 2014, 31(1): 115-120.  Abstract ( )   PDF (1303KB) ( )   With density functional B3P86 method and cc-PV5Z base,bond lengths,dipole moments,vibration frequencies and other physical parameters of BH molecule in external electric fields are obtained.With analysis of physical parameter,scope of dissociation field is determined,appropriate parameters to scan single point energies are set,and potential energy curves are obtained.It shows physical parameters and potential energies in external electric fields,especially in reverse electric fields.Potential energy function without electric field is fitted by Morse potential.Fitting parameters are in good agreement with experiment.Potential energy under external electric fields is fitted using a potential model,which is constructed with dipole approximation.Critical electric parameters are calculated.They are consistent with other numerical results,so the model is reliable and accurate.It provides theoretical reference for molecular spectroscopy,dynamics and cooling with Stark effect.

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An Improved Optimized Method for Periodic Coulomb Potential LI Mingrui, ZHOU Gang, CHU Zhe, MA Kun, QIAN Bingwen 2014, 31(1): 121-126.  Abstract ( )   PDF (1780KB) ( )   Optimization method for Coulomb potential by Natoli was improved,in which simple polynomial basis functions are used to fit slowly varying long-rang part of potential,and limited conditions are set to enhance consistency.Without increasing computational complexities,an optimal potential with lower mean squared difference is obtained.Cutoff criterion in real and reciprocal space determining optimal breakup of exact potential is suggested kcrc ≥ 15.New potential was tested on dense liquid hydrogen which shows lower pressure and energy than Natoli and Ewald potentials.