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25 May 2018, Volume 35 Issue 3 Previous Issue    Next Issue

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Practices and Advances on Rational Subgrid-Scale Modeling FANG Le, WANG Chuhan 2018, 35(3): 253-261.  DOI: 10.19596/j.cnki.1001-246x.7800 Abstract ( )   HTML ( )   PDF (2266KB) ( )   Subgrid-scale modeling is spirit of large-eddy simulation. Original intention of rational subgrid-scale modeling is to remove empirical and phenomenological components of modeling process, so that every step in modeling process is physically and mathematically traceable. According to theory of rational subgrid modeling, we developed a series of subgrid models that do not depend on empirical constants and phenomenological models, but their effect in practical problems is still insufficient, which leads to, in recent years, reflection on proper idea of subgrid modeling. This paper reviews existing research and new progress, whose goal is to give a rational and self-consistent theoretical guidance of future large eddy simulation.

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Embedding of Constitutive Iterative Algorithm in LS-DYNA JIANG Dong, LI Yongchi 2018, 35(3): 262-268.  DOI: 10.19596/j.cnki.1001-246x.7636 Abstract ( )   HTML ( )   PDF (2212KB) ( )   We developed and improved constitutive model, using LS-DYNA second development technology to embed a damaged Johnson-Cook constitutive model of commercial finite element software.Detailed description of structure of iterative algorithm and calculation process are presented. For experiments of perforation of 12 mm thick steel plates by 20 mm diameter projectiles with flat and conical noses, numerical simulations are carried out. Calculation and experiment results are consistent well. It indicates that constitutive algorithm, containing damage constitutive model and damage evolution equation are reasonable and reliable.

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A Modified Finite Integration Method for Convection-Diffusion-Reaction Problems SUN Tingting, HAN Saisai, XU Mingtian 2018, 35(3): 269-274.  DOI: 10.19596/j.cnki.1001-246x.7632 Abstract ( )   HTML ( )   PDF (878KB) ( )   Finite integration method is employed to solve convection-diffusion equations. For diffusion-dominated convection-diffusion problems, numerical results show that finite integration method is more than one and two orders of magnitude better in accuracy than QUICK scheme and central differencing scheme, respectively. We find that finite integration method can be improved by introducing a weighting parameter in numerical quadrature. By appropriately adjusting the parameter, modified finite integration method is at least more than four orders of magnitude better in accuracy than traditional finite volume method for convection-dominated flows. Furthermore, even coarse grids are utilized to divide flow domain modified finite integration method has not lead to unphysical oscillations in convection-dominated convection-diffusion problem, which demonstrates a good stability of the method.

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Coalescence of Asymmetrically-arranged Droplets on Topographic Substrates LIN Yuxi, YE Xuemin, LU Lifang, LI Chunxi 2018, 35(3): 275-284.  DOI: 10.19596/j.cnki.1001-246x.7628 Abstract ( )   HTML ( )   PDF (3068KB) ( )   Coalescence of two surfactant-containing droplets on a topographic substrate was modeled with lubrication theory considering asymmetrically-arranged configuration. Effects of initial droplet spacing and height of substrate on coalescence evolution were investigated and compared with symmetrically-arranged droplets. It shows that variation of droplet height undergoes five stages, and variation of surfactant concentration experiences three stages in a short period; Coalescing time of droplets and surfactant is extended with increasing droplet spacing while shorten with increasing substrate height; Coalescence time of asymmetric droplets is distinctly less than that of symmetric droplets, resulting in a faster rate of coalescence.

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Numerical Simulation of Planar Moving Shock Interacting with a Single Row of Water Columns and Multi-material Interfaces ZHAO Qi, ZHANG Mengping, XU Shengli, LU Jianfang 2018, 35(3): 285-293.  DOI: 10.19596/j.cnki.1001-246x.7635 Abstract ( )   HTML ( )   PDF (4891KB) ( )   A moving planar shock interacting with multi-material interfaces in compressible fluid on fixed Descartes grids is studied. Level-set method combined with a revised real ghost fluid method(rGFM) are applied for tracking gas-water and gas-solid interfaces, where a revised Riemann problem is constructed and its approximate solutions are populated for real and ghost fluid status. WENO schemes are employed for Euler and level-set equations. Numerical schlieren images are obtained for demonstrating shock evolution. Complex shock structures distinguish accurately and show various interfaces embedded in the fluid. Other than partition and coordinate transformation, we offer an approach for computation of complex flow field on Descartes grids involving multi-material interfaces or objects.

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Mechanical Deformation of Myocardial Tissue with Cellular Automaton ZHANG Xueliang, TAN Huili, TANG Guoning, DENG Minyi 2018, 35(3): 294-302.  DOI: 10.19596/j.cnki.1001-246x.7659 Abstract ( )   HTML ( )   PDF (2684KB) ( )   Effect of mechanical deformation on spiral waves in myocardial tissue is studied with Greenberg-Hastings cellular automaton. It shows that for stable spiral waves existing in a regular lattices system, physiological deformation leads to meandering but not breakup of spiral waves. However, pathological deformation results in breakup, meandering, or disappearance of spiral waves. Simulation results show that spiral waves are more sensitive to amplitude than to angular frequency of mechanical deformation. The quick recovery of a sportsman after hitting on breast and fibrillation coming from violent hitting on breast was explained.

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Heat and Mass Transfer Characteristics Around Slip Single Coal Particle in Flue Gas in High Intensity Sound Field XU Weilong, JIANG Genshan, AN Liansuo, LIU Yuechao 2018, 35(3): 303-312.  DOI: 10.19596/j.cnki.1001-246x.7656 Abstract ( )   HTML ( )   PDF (4366KB) ( )   To study heat and mass transfer around pulverized coal particle under high intensity acoustic field with superposed steady component, two-dimensional, unsteady, laminar conservation equations for mass, momentum and energy transport in flue gas phase of power plant boiler were developed. Local Nusselt, space-averaged Nusselt and space- and time-averaged Nusselt numbers around coal particles, as functions of sound pressure level, frequency and ratio of acoustic velocity to steady slip velocity between particles and main flow, were discussed. There exists extremum frequency in which heat and mass transfer effect is the best in the range of audible sound frequency. It highlights a good application prospect in combustion for boiler.

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Time-Domain Microwave Breast Screening Technique with Reconstructing Cole-Cole Model Parameters LIU Guangdong, YU Guangqun 2018, 35(3): 313-320.  DOI: 10.19596/j.cnki.1001-246x.7638 Abstract ( )   HTML ( )   PDF (2477KB) ( )   A novel time-domain technique for microwave tomography imaging is proposed. In the methodology three main difficulties, nonlinearity and ill-posedness of microwave imaging problem, and dispersion characteristics of breast tissues, are effectively circumvented by nonlinear optimization method, regularization technique, and introduction of a Cole-Cole model, respectively. It is preliminarily confirmed by a two-dimensional numerical example in which noise is considered. It shows that the inversion technique is feasible to detect small breast tumors. It is easy to find shallow tumors and accuracy in estimating static conductivity is best.

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Identification of Channel Geometry with Level Set Based Two-stage MCMC Method MA Xianlin, ZHOU Desheng 2018, 35(3): 321-329.  DOI: 10.19596/j.cnki.1001-246x.7650 Abstract ( )   HTML ( )   PDF (6651KB) ( )   Channel geometry is represented by a signed distance function, and boundaries are then updated gradually by solving level set equation and matching of production historical data using two-stage Markov chain Monte Carlo (MCMC) method. In the first stage, streamline-derived sensitivities are employed to approximate a likelihood function, and instrumental proposal distribution of MCMC is modified by the approximation. In the second stage, proposals that pass the first stage are further assessed by running full numerical simulations, and a precise likelihood function is acquired. The models are checked for acceptance with modified acceptance probability. Finally, a 2D example demonstrates effectiveness of the method.

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Application of Protein-specific Polarized Charge on HIV-1 Protease-Inhibitor Binding Free Enengy LI Yuchen, FENG Guoqiang, DUAN Lili 2018, 35(3): 330-334.  DOI: 10.19596/j.cnki.1001-246x.7752 Abstract ( )   HTML ( )   PDF (786KB) ( )   Molecular dynamics simulations up to 10 ns are carried out to study binding of inhibitor to HIV-1 protease using standard AMBER force field and polarized protein-specific charge (PPC). Binding free energy was calculated by MM/PBSA method.PPC is derived from quantum mechanical calculation for protein in solution and therefore it includes electronic polarization effect. It shows that binding free energy calculated with PPC charge is closer to experimental result than that with AMBER force field.

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Molecular Structure and Spectrum of Aflatoxin B1 Under External Electric Fields HE Junbo, LIU Yuzhu, LIN Hua, GE Yingjian, HAN Shun 2018, 35(3): 335-342.  DOI: 10.19596/j.cnki.1001-246x.7644 Abstract ( )   HTML ( )   PDF (2499KB) ( )   To study influence of external field on aflatoxin B1 (AFB1), density functional theory on level of 6-311G is utilized. Total energy, dipole moments, geometric parameters, energy gap and infrared spectra under different external fields (from 0 to 0.015 a.u.) are obtained, respectively. UV-Vis spectra absorption of AFB1 and excitation states are calculated with time dependent density functional theory method. It shows that total energy increases, while dipole moment decreases. Molecular geometric parameter and energy gap are strongly dependent on increasing field intensity. Two ultraviolet absorption peaks of AFB1 show reversed shifts. Excitation energies decrease, which indicates that AFB1 molecule is unstable under external fields.

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Wavepacket Dynamics Study of Photoassociation Reaction of HeH+ System WANG Binbin, HAN Yongchang 2018, 35(3): 343-349.  DOI: 10.19596/j.cnki.1001-246x.7750 Abstract ( )   HTML ( )   PDF (1168KB) ( )   Optimal photoassociation (PA) reactions of He+H+→HeH+ in electronic ground state, together with relevant multiphoton transition and dissociation processes, are investigated with time-dependent quantum wavepacket method. Level v=6 is set to target state and optimal PA probability of this level is obtained by optimizing laser parameters. It is shown that with increase of initial collision momentum of collision pair optimal laser duration is decreasing, but laser intensity and detuning increasing. Due to resonance multiphoton transition process, other bound levels may be resided after PA process at some collision momenta. In addition, above threshold dissociation increases linearly up to a maximum, then decrease to a saturation value and dominates dissociation processes at relative greater initial collision momentum.

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A First-Principles Study on Electronic and Optical Properties of Distorted Perovskite DyMnO3 CAI Lugang 2018, 35(3): 350-356.  DOI: 10.19596/j.cnki.1001-246x.7645 Abstract ( )   HTML ( )   PDF (1363KB) ( )   Ground-state electronic structure and optical properties of distorted perovskite DyMnO3 are investigated in the frame of density functional theory within generalized gradient approximation (GGA). Optimized lattice constants are reasonable in agreement with experimental data. Electronic band structure, density of states and partial density of states of elements are obtained. It shows that DyMnO3 exhibit an indirect band gap of 0.91 eV. Dielectric function, optical reflectivity, refractive index, extinction coefficient, electron energy loss, and absorption coefficient are calculated and analyzed for radiation up to 35 eV.

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Theoretical Study on Multiple Exciton Generation of Si6X(X=Cu,Ag and Au) Clusters GAO Feng, YANG Chuanlu, WANG Meishan, MA Xiaoguang, LIU Wenwang 2018, 35(3): 357-364.  DOI: 10.19596/j.cnki.1001-246x.7751 Abstract ( )   HTML ( )   PDF (3771KB) ( )   Multiple exciton generation (MEG) of Si6X(X=Cu, Ag and Au) clusters is investigated by using symmetry adapted cluster theory with configuration interaction and pseudo potential LANL2DZ basis set. Before MEG calculations, geometrical structures of clusters are optimized and their energy stabilities are confirmed by frequency analysis based on density functional theory method and all-electron double zeta valence quality plus polarization functions primary basis sets DZP-DKH. It indicates that double exciton is found dominating component and MEG of clusters appear in visible range although the strong part is in ultraviolet light range, which provides information for potential materials utilizing MEG to harvest energy of solar light.

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First-Principles Study of Thermoelectric Transport Properties of β-Antimonene WANG Wenhua, ZHAO Guojun, WANG Shudong 2018, 35(3): 365-372.  DOI: 10.19596/j.cnki.1001-246x.7640 Abstract ( )   HTML ( )   PDF (5754KB) ( )   First-principles and semiclassical Boltzmann transport formalism are employed to investigate thermoelectric properties of β-antimonene. We obtain phonon dispersion, phonon group velocity, phonon relaxation time, lattice thermal conductivity and Seebeck coefficient, electrical conductivity and electron thermal conductivity as functions of chemical potential of β-antimonene. It indicates that longitudinal acoustic (LA), transverse acoustic (TA), and z-direction acoustic (ZA) branches of β-antimonene are linear near Γ point due to its buckling structure. Acoustic phonon contribution to whole lattice thermal conductivity is as high as 96.68%, and optical phonon accounts for 3.32% only. A large a-o gap leads to LA be dominant in group velocity and relaxation time, and thus increasing LA phonon contribution to whole thermal conductivity. In addition, merit ZT increases with temperature, and reaching a maximum of 0.275 at 700 K near Fermi level.

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Effect of End Shape on Magnetization Reversal Dynamics of NiFe Nanofilm Elements ZHANG Guangfu, DENG Yangbao, TIAN Ye, JIANG Lianjun 2018, 35(3): 373-378.  DOI: 10.19596/j.cnki.1001-246x.7655 Abstract ( )   HTML ( )   PDF (9316KB) ( )   Magnetization reversal dynamics of NiFe nanofilm elements were studied with micromagnetic simulation. Magnetization reversal and spin-wave dynamic properties are effectively tuned by tailoring end shape of NiFe nanofilm elements. As magnetization reversal occurs,it is accompanied by a soft magnetic mode whose spacial symmetry determines initial steps(onset) of microscopic magnetization phase transitions path. There exists a critical tapered parameter h0. For elements with tapering parameter h<h0, reversal is achieved by nucleation of reversed domain at element ends and its irreversible expansion through domain wall movement toward central area of element. It is softening of edge mode that triggers magnetization reversal. For elements with h ≥ h0, reversal is realized by quasi-uniform rotation of magnetization, which is induced by softening of fundamental mode.>