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25 March 2018, Volume 35 Issue 2 Previous Issue    Next Issue

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MMALE Method Based on Interface Capture for Three-Dimensional Multi-Material Radiation Hydrodynamics Equation GUO Shaodong, JIA Zupeng, XIONG Jun, ZHOU Haibing 2018, 35(2): 127-137.  DOI: 10.19596/j.cnki.1001-246x.7599 Abstract ( )   HTML ( )   PDF (6612KB) ( )   Mixed cells are introduced in multi-material arbitrary Lagrangian-Eulerian (MMALE) method to capture material interfaces. An energy-preserving closure model on mixed cells for diffusion equation is proposed. Based on closure model, a method for coupling multiple material radiation diffusion simulation and hydrodynamics MMALE simulation is proposed. Numerical experiment with analytical solution shows accuracy of the method for diffusion equation. Results of Sedov and spherical implosion problems show that the method is effective and robust. Comparisons with traditional Lagrangian method prove advantages of the method.

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Uncertainty Quantification of Electron EOS in Temperature-and-Density Dependent Atomic System MENG Xujun, WANG Ruili 2018, 35(2): 138-150.  DOI: 10.19596/j.cnki.1001-246x.7596 Abstract ( )   HTML ( )   PDF (5789KB) ( )   By using temperature-and-density dependent atomic models, a method for uncertainty of electron EOS of plasmas is described via 35 functional exchange-correlation potentials. A fast method for roughly evaluating uncertainty is designed, and checked in Thomas-Fermi model. Taking gold as an example, calculations of uncertainties of total inner energy, electron pressure and ionization degree, with their ‘quasi true value’, are carried out in the range of temperatures from 1.0 to 10 000.0 eV with three densities 1.0, 10.0, 100.0 g·cm-3,respectively. The results can be applied in engineering design.

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Parallel Finite Element Computation of Incompressible Viscous Flows Based on Block Preconditioning Strategy LI Lingxiao 2018, 35(2): 151-160.  DOI: 10.19596/j.cnki.1001-246x.7627 Abstract ( )   HTML ( )   PDF (5733KB) ( )   A parallel finite element solver is developed for simulation of the unsteady incompressible viscous flows. Implicit mid-point scheme is used to discretize time variable. Based on unstructured grid, velocity and pressure are discretized by classical P2-P1 Taylor-Hood mixed finite element. Resulting linear algebraic systems are large-scale, sparse, non-symmetric and ill-conditioned. Using a specially designed iterative strategy, it is solved by preconditioned GMRES method with modified pressure-convection-diffusion(PCD) preconditioner. A number of numerical experiments verify scability and validity of the solver. Especially, driven cavity flow simulation in 3D (Re=3200.0) clearly shows existence of primary eddy, downstream secondary eddy, upstream secondary eddy, end-wall vortices and T-G-like vortices. A parallel efficiency comparison with least-squares commutator(LSC) preconditioner is also given.

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A Penalized Finite Element Method of Nonlocal Diffusion Problem with Volume Constraints GE Zhihao, WU Huili 2018, 35(2): 161-168.  DOI: 10.19596/j.cnki.1001-246x.7730 Abstract ( )   HTML ( )   PDF (1515KB) ( )   We propose a finite element method, penalized finite element method, to solve a homogenous and inhomogenous nonlocal diffusion problem with volume constraints, and give error estimate of the method. Finally, we show numerical experiments to verify the theoretical results.

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Anslysis of Kinetic Energy Dissipation Rate and POD Reconstruction of a Channel Flow CHEN Bin, LIU Ge 2018, 35(2): 169-177.  DOI: 10.19596/j.cnki.1001-246x.7619 Abstract ( )   HTML ( )   PDF (6271KB) ( )   Vortex wave flow field within a channel was measured using particle image velocimetry (2DPIV). Instantaneous velocity vector field measured was reconstructed with dominant modes using POD technology. Average velocity and turbulent kinetic energy distribution were obtained using POD reconstructed field. Turbulent kinetic energy dissipation rate was estimated by using a large eddy PIV method. It shows that dominated structure of original flow field were characterized by reconstruction of flow field. Noise and other interference information were eliminated. Large eddy PIV method estimates effectively distribution of kinetic energy dissipation rate. Turbulent kinetic energy is small in vicinity of wall. Turbulent kinetic energy increases near center of channel region, which is characteristics of jet. Kinetic energy dissipation rate peak appears in vicinity of central region and channel wall. Away from wall kinetic energy dissipation rate is increases initially, and decreased gradually until it reaches a peak.

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Dynamical Stability of Traveling Wave Solutions to KdV-Burgers Equation SHI Yuren, FENG Wenxing, XI Zhonghong, ZONG Jin, SONG Zongbin, PANG Jungang 2018, 35(2): 178-186.  DOI: 10.19596/j.cnki.1001-246x.7617 Abstract ( )   HTML ( )   PDF (4746KB) ( )   We made linearization stability analysis on traveling wave solutions of KdV-Burgers equation. Numerical results indicate that traveling waves are dynamically stable for positive-dissipation case, while they are dynamically unstable for negative-dissipation case. Then we presented a finite difference scheme, which is conditionally stable, for long-time evolution of perturbed traveling waves. Numerical results also show that traveling waves are dynamically stable as positive-dissipation is held. Our results modify and improve conclusions given in relative literatures.

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Influence Factors in Two-Dimensional Plasma Density Reconstruction LI Xuemei, WANG Yuhua 2018, 35(2): 187-193.  DOI: 10.19596/j.cnki.1001-246x.7611 Abstract ( )   HTML ( )   PDF (743KB) ( )   Two-dimensional density distributions of dense plasmas in laser confinement fusion are revealed with proton imaging. Simultaneous iterative reconstruction algorithm (SIRT) is used to study influence factors of two-dimensional plasma density reconstruction. Effects of plasma density gradient, magnitude of density and initial proton energies on reconstruction errors are investigated. Importance of figuring out rough area and range of simulated plasma zone before simulation is analyzed. Furthermore, an analytical expression between reconstruction errors and noises is established through data analyses.

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Model Coefficient Revision on Supersonic Turbulent Pulse for Aero-Optic Effect PAN Honglu, LI Junhong, CHENG Xiaoli, MA Handong 2018, 35(2): 194-204.  DOI: 10.19596/j.cnki.1001-246x.7603 Abstract ( )   HTML ( )   PDF (13427KB) ( )   Aero-optic effect is investigated in supersonic/hypersonic flow. Flat plate, ramp and cave model in supersonic/hypersonic flow condition are studied with large eddy simulation (LES). Turbulent density pulse is predicted to verify coefficient of density pulse model-mixing length (ML) model. It indicates that LES method simulates turbulent density pulse well in flat plate boundary layer flow, oblique shock wave/boundary layer interaction and strong separation flow. Density pulse data obtained by LES is used to verify ML coefficient and set a quantitative result. The modified ML was used to predict aero-optical effect on missile successfully.

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Method of Moment for Electromagnetic Scattering from Ground Covered with Snow TIAN Wei, REN Xincheng 2018, 35(2): 205-211.  DOI: 10.19596/j.cnki.1001-246x.7608 Abstract ( )   HTML ( )   PDF (932KB) ( )   To investigate electromagnetic scattering from layered rough surface by method of moment, a direct domain decomposition method is used to derive electromagnetic integral equation of layered rough surface. Combining with wave equation and Green's function, electromagnetic integral equations of layered rough surface are obtained by applying Green's theorem to each space divided by rough surface. Then integral equation is discretized using method of moment. Angular distributions of electromagnetic scattering coefficient from ground covered with snow are obtained with numerical calculation, in which snow surface and ground are described with 1D band-limited Weierstrass fractal spectrum and Monte Carlo method. Accuracy of the domain decomposition is demonstrated by finite difference time domain results. Through analyzing scattering coefficient that varies with parameters of snow and ground, medium parameters of snow and soil, parameters of incident wave, the complete scattering characteristics are obtained.

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Identification of Thermal Conductivity for Transient Heat Conduction Problems by Improved Cuckoo Search Algorithm ZHOU Huanlin, YAN Jun, YU Bo, CHEN Haolong 2018, 35(2): 212-220.  DOI: 10.19596/j.cnki.1001-246x.7600 Abstract ( )   HTML ( )   PDF (896KB) ( )   An improved cuckoo search (ICS) algorithm is developed to identify temperature dependent thermal conductivity for transient heat conduction problems. Kirchhoff transformation is adopted to transform nonlinear transient heat conduction problems into linear problems. The direct problems are solved by boundary element method. Inversion of thermal conductivity is transformed to estimate unknown coefficients, which is solved by ICS algorithm. ICS algorithm is less sensitive to iterative initialization than conjugate gradient method and ICS algorithm has high efficient convergence compared with cuckoo search (CS) algorithm. For ICS, numerical examples indicate that increase of measured point number causes increase of iteration numbers, whereas increase of nest number decreases iteration numbers. The less the measured noise is, the higher the precision of results is. Iteration numbers decrease at the same time. It shows that ICS algorithm is an accurate and efficient method for identification of thermal conductivity.

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Calculation of Structural Parameters and Frontier Orbital of Cucurbituril (5-10) with Density Functional Theory LIN Yan, LIU Yun, PENG Qingwei, WEI Xiaonan, TANG Yanlin 2018, 35(2): 221-229.  DOI: 10.19596/j.cnki.1001-246x.7631 Abstract ( )   HTML ( )   PDF (4413KB) ( )   In gas phase, structure of cucurbituril (CB[n],n=5-10) composed of n glycoluril units was optimized by density functional theory (DFT). Structural parameters, frontier orbital energy levels and chemical stability of CB[n](n=5-10) were calculated and analyzed with conceptual DFT reactivity index and Multiwfn wave function analyzer. It showed that structure of C-N bond is most stable, chemical stability of α=O, γ-γ, γ-H and β-H(2) is poor. Change of part bond angle is bounded by CB[6], and change of main dihedral angle exhibits symmetrical. Port diameter, cavity diameter and outer diameter of CB[n](n=5-10) tend to increase linearly with increase of number of glycoluril units. EHOMO, ELUMO and ELUMO-EHOMO of CB[n](n=5-10) reduced, their chemical activity increased and stability decreased with increase of number of glycoluril units. The largest electrophilic active sites are located at port O atoms. Electron cloud distribution of LUMO is mainly related to H atoms,and contribution of methine H atom to LUMO electron cloud is the largest. Methine C atom, methylene C atom, and methylene atom H in direction of CB[n] port have an inhibitory effect on electron cloud distribution of LUMO. Inhibitory capacity is methylene H atom in direction of CB[n] > methylene C atom > methine C atom. It provides theoretical basis for study of supramolecular assembly of cucurbituril.

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Physical Properties and Spectra of BrCl Molecule Under External Electric Field ZHANG Xiangyun, LIU Yuzhu, YIN Wenyi, MA Xinyu, QIN Chaochao 2018, 35(2): 230-234.  DOI: 10.19596/j.cnki.1001-246x.7610 Abstract ( )   HTML ( )   PDF (1410KB) ( )   Ground states of BrCl in different electric fields from 0 to 0.035 a.u. are optimized by HF(Hartree-Fock) theory at 6-31+G(d,p) basis sets. Optimized parameters, dipole moment, total energy, bond length, charge distribution, the highest occupied molecular orbital energies, the lowest unoccupied molecular orbital energies, energy gap, infrared spectrum and dissociation potential energy surface(PES) are obtained. It shows that with increasing external field from 0 to 0.035 a.u. along molecular axis Z (Br-Cl bond direction), molecular total energy increasing firstly, then decreasing, while bond length and dipole moment decreases at beginning and then increases. Energy gap decreases and atomic charge distribution increases with increasing electric field. IR vibration spectrum of BrCl molecule shows an observable blue shift firstly and then red shift with increasing of external electric field. External electric field of 0.045 a.u. is enough to induce degradation of BrCl with Br-Cl bond breaking. It provides reference for degradation of BrCl in external electric field.

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Influence of Contact Geometry on Electrical Transport Properties of Si4 Cluster: First Principles Study LIU Futi, ZHANG Shuhua, CHENG Xiaohong 2018, 35(2): 235-241.  DOI: 10.19596/j.cnki.1001-246x.7602 Abstract ( )   HTML ( )   PDF (4509KB) ( )   Influence of contact geometry including coupling morphology and distances on electrical transport properties of Si4 cluster coupled to two atomic Au(100)-3×3 electrodes is investigated from first principles with a combination of density functional theory and non-equilibrium Green's function method. Following situations of coupling morphology are considered:Si4 cluster is sandwiched between two atomic Au electrodes at top to top, top to hollow, hollow to hollow position. We optimize geometry of junctions at different distances. We calculate cohesion energy and conductance of junctions as a function of distance dz, and simulate Au-Si4-Au junctions breaking process. We obtain equilibrium conductances of the most stable structures for different coupling morphology. They are 0.71 G0, 0.96 G0, 2.44 G0, respectively. All junctions at stable structure have great conductance. In the range of voltage from -1.2 V to 1.2 V, I-V curve of junctions in the most stable structure shows linear characteristics. It shows that conductance is sensitive to coupling morphology and contact distance.

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Electrical Characteristics of Coaxial-Annular Through Silicon Via WANG Fengjuan, WANG Gang, YU Ningmei 2018, 35(2): 242-252.  DOI: 10.19596/j.cnki.1001-246x.7615 Abstract ( )   HTML ( )   PDF (5840KB) ( )   For coaxial-annular through silicon vias (CA-TSV) structure with superior performances, characteristic impedance, power, time constant and analytical models of parasitic parameters are proposed and effects of structural parameters on electrical properties are studied. S21 parameter was verified by software HFSS. It shows that increasing inner diameter of CA-TSV or reducing outer diameter reduces characteristic impedance, while reducing inner diameter of CA-TSV or increasing outer diameter reduces its power consumption effectively. Increasing inner diameter of CA-TSV or outer diameter reduces time constant of RC equivalent circuit, whereas increasing inner diameter of CA-TSV or reducing outer diameter reduces time constant of RL equivalent circuit. Increasing inner diameter of CA-TSV or outer diameter reduces resistance effectively and capacitance can be increased significantly. It provides reference for electrical properties of three-dimensional integrated circuits based on TSV interconnects.