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25 July 2019, Volume 36 Issue 4 Previous Issue    Next Issue

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Path Integral Monte Carlo Calculations of Equation of State of Hydrogen ZHANG Qili, LIU Haifeng, LI Qiong, SONG Hongzhou, ZHANG Gongmu 2019, 36(4): 379-385.  DOI: 10.19596/j.cnki.1001-246x.7855 Abstract ( )   HTML ( )   PDF (2461KB) ( )   We computed equations of state of hydrogen in warm dense matter regime by using DPIMC method. In large part of the regime, pressure difference between DPIMC and RPIMC is less than 10%. In low temperature regime, some difference beyond 20%. We pointed out two clerical errors in pressure of RPIMC. In dissociation and ionization regime, pressures of DPIMC lie between results of TF and TFC model. In dissociation regime, the largest pressure difference between DPIMC and RPIMC is 15%. In ionization regime, pressures of DPIMC are agree with RPIMC. In low density regime, internal energies of DPIMC are close to those of RPIMC, less than those of QMD and those of IG model. In high density regime, pressures of DPIMC lie between results of TFC and IG model, internal energies of DPIMC less than those of IG model.

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Discrete Unified Gas Kinetic Scheme for Porous Media Flow at Representative Elementary Volume Scale CHEN Xijun, GUO Zhaoli 2019, 36(4): 386-394.  DOI: 10.19596/j.cnki.1001-246x.7876 Abstract ( )   HTML ( )   PDF (10601KB) ( )   DUGKS is extended to model porous media flow at representative elementary volume scale combined with generalized porous media model. It is verified by several two-dimensional classical problems:Poiseuille flow, Couette flow and cavity flow. Effectiveness of DUGKS for porous media flow is tested and advantage of DUGKS in grid flexibility is demonstrated. A fracture system is modeled by DUGKS for porous media flow.

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Lattice Boltzmann Simulation of Particle Sedimentation Considering Micro-scale Gas Rarefaction Effect MU Zhiyu, LIU Zhenyu, WU Huiying 2019, 36(4): 395-402.  DOI: 10.19596/j.cnki.1001-246x.7901 Abstract ( )   HTML ( )   PDF (3564KB) ( )   Sedimentation of micro particles in a narrow microchannel was simulated with multiple-relaxation-time lattice Boltzmann model. Influence of gas rarefaction, initial position of particle and interaction between particles on sedimentation process is analyzed. It is found that gas rarefaction effect becomes obvious with increase of Knudsen number. And the effective viscosity of gas is decreased. At the same time, slip velocity on the surface of particle increases and viscosity resistance of particle decreases, which results in an increase of particle equilibrium velocity. For different initial positions of particle, there exists a significant difference in sedimentation process. It reveals that horizontal motion of micro particle exists besides moving in the vertical direction. And the particle has oscillating tendency before stabilizing on the central position in horizontal direction. For DKT phenomenon in microscale, rarefaction effect is obvious on trajectory of particles and the drafting process is prolonged.

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Numerical Analysis of Kelvin-Helmholtz Instability in Inclined Walls YAO Mengjun, SHANG Wenqiang, ZHANG Ying, GAO Hui, ZHANG Daoxu, LIU Peiyao 2019, 36(4): 403-412.  DOI: 10.19596/j.cnki.1001-246x.7882 Abstract ( )   HTML ( )   PDF (10681KB) ( )   Kelvin-Helmholtz instability of two-dimensional immiscible incompressible fluid in a sloping tube was numerically simulated with front tracking method. Effects of inclined angles of wall, thickness of velocity gradient layer and Richardson number on development of K-H instability were investigated. It shows that the greater the angle of wall inclination is, the faster the K-H instability develops and the more liquid is rolled up. It was also found that increase of thickness of the velocity gradient layer under the inclined wall presented an inhibitory effect on roll-up of the interface. The greater gravity items of Richardson number is, the slower the interface rolls up. However, surface tension items of Richardson number have weak effect on the growth of interface.

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A Pressure-based Algorithm for Numerical Simulation of One-dimensional Two-phase Flow WANG Zhi, ZOU Gaoyu, GONG Jing, BAI Jianfeng, ZHAI Bowen 2019, 36(4): 413-420.  DOI: 10.19596/j.cnki.1001-246x.7892 Abstract ( )   HTML ( )   PDF (2147KB) ( )   Two-phase flow is studied numerically using a one-dimensional two-fluid equation system. A hyperbolic type of governing equation is applied. The segregated solution method is promoted and adopted. By establishing mass conservation based pressure correction, SIMPLE algorithm is extended to two-phase flow simulations. Numerical results for well-known two-fluid air/water flow benchmark problems are presented and discussed.

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A Method to Calculate Critical Magnetic Field of PM-FM Transformation MA Wenjie, ZHANG Ping 2019, 36(4): 421-426.  DOI: 10.19596/j.cnki.1001-246x.7857 Abstract ( )   HTML ( )   PDF (5141KB) ( )   Based on linear spin wave approximation and Hellmann-Feynman theorem, we introduce a method to calculate critical magnetic field where the ground state transforms into a fully polarized ferromagnetism as magnetic field is applied. To confirm our method, we apply it to two models and compare results with numerical data.

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Influences of c/uA and mi/me on Magnetic Reconnection Process QIAN Renfeng 2019, 36(4): 427-439.  DOI: 10.19596/j.cnki.1001-246x.7881 Abstract ( )   HTML ( )   PDF (7859KB) ( )   A finite difference scheme to control divergence error of electromagnetic field is proposed to study magnetic reconnection. With this simple numerical scheme, divergence errors of electromagnetic field are limited in the magnitude of rounding error. Our results are in good agreement with that in GEM. Influences of c/uA and mi/me on magnetic reconnection are also studied. It indicated that with the increase of c/uA, net charge densities decrease while reconnection rate remains almost unchanged. The increase of mi/me could lead to current sheet thinning and acceleration of reconnection.

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Three-dimensional Fractal Reconstruction Technique and Leakage Characteristics of Micro-pore Sealing Interfaces XU Guoliang, ZHU Yiping, FANG Lin, DU Yang, HUANG Xiaoming 2019, 36(4): 440-448.  DOI: 10.19596/j.cnki.1001-246x.7889 Abstract ( )   HTML ( )   PDF (9641KB) ( )   Fractal characteristics of interface micro-porous structure is studied in detail with three-dimensional numerical reconstruction technology of fractal rough surface. An interfacial leakage mechanism model is built based on fractal porous media transport theory. Relation between microscopic morphology and macroscopic leakage rate is obtained. Contact behavior of a single asperity is simulated with finite element analysis, and deformation displacement of the maximum aperture is obtained. Effective coupling between microscopic contact mechanics and microscopic leakage model is achieved. Results of prediction model are in good agreement with experimental results in predicting metal gasket leakage rate. It is found that fractal dimension, and characteristic scale coefficient of rough surface and deformation displacement have great influence on geometry morphology of interface microporous structure, and therefore, are key factors of interfacial leakage rate.

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Regularity of Gas Leakage from Underground Chemical Explosions Based on Dimensional Analysis and Darcy's Law ZHONG Wei, TIAN Zhou, WANG Tieliang 2019, 36(4): 449-456.  DOI: 10.19596/j.cnki.1001-246x.7886 Abstract ( )   HTML ( )   PDF (2517KB) ( )   For underground chemical explosions in a cavity surrounded by uniform rock media, regularity of gas leakage was studied. Firstly, with method of dimensional analysis, influence physical quantities of gas leakage time, such as gas dynamic viscosity, overpressure of cavity, porosity of surrounding rock and ratio of the square of surrounding rock's thickness to permeability, were obtained. Qualitative functional relation of these quantities was proposed. Then, on the basis of Darcy's law, analytical formula for gas leakage time was derived. It agrees well with the qualitative functional relation derived with dimensional analysis method. Namely, two functions derived from totally different ways are highly compatible with each other. The method proposed is an enlightening idea and an efficient technique for theoretical analysis and regularity research of underground explosions gas leakage. It provides references for engineering estimation.

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Chebyshev Rational Approximation Method for Activation Property Calculations of Radioactive Nuclides ZHANG Binhang, YUAN Xianbao, ZHANG Yonghong, TANG Haibo 2019, 36(4): 457-464.  DOI: 10.19596/j.cnki.1001-246x.7894 Abstract ( )   HTML ( )   PDF (5912KB) ( )   AMY is a newly-developed code of handling neutron induced transmutation and activation in materials. The code is based on Chebyshev rational approximation method (CRAM) to solve Bateman equations and to deal with complex pattern of chains produced by sequences of neutron reaction processes.Varieties of material activation properties are provided in AMY, including activity, decay heat, biological hazard, dose rate, clearance index and gamma source spectra. In order to verify the code, basic nuclear database in handbook of activation data was selected for comparing with FISPACT-2007. It shows that results of AMY are in good agreement with FISPACT-2007, and calculation efficiency of AMY is slightly higher than FISPACT-2007.

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Fast Inversion of Array Laterolog Based on Adaptive Differential Evolution Algorithm NI Xiaowei, XU Sihui, FENG Jiaming, LIU Diren 2019, 36(4): 465-473.  DOI: 10.19596/j.cnki.1001-246x.7858 Abstract ( )   HTML ( )   PDF (8749KB) ( )   In strict sense of electric log inversion, multiple forward calculations are performed many times during each iterative procedure of inversion algorithm, which takes a long time. In particularly, real-time inversion of electrolog data is unlikely to be achieved in complex three-dimensional stratigraphic models. There is a great challenge to process efficiently electrolog data in real time. In this paper, based on radial step medium model, forward response is pre computed and linear interpolation is called directly in inversion process, which greatly saves inversion time. An adaptive differential evolution algorithm is proposed to transform array lateral inversion problem into a nonlinear global optimization problem. Compared with classical differential evolution algorithm and Marquette algorithm, the adaptive differential evolution algorithm has characteristics of high search success rate (90%), low average number of iterations (21), and good noise immunity. The algorithm is tested under layered media model with different invasive conditions. Resistivity using the algorithm is closer to the true resistivity than apparent resistivity, which meets evaluation needs of oil and gas reservoirs.

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Molecular Dynamics Simulation of Wettability of Calcite and Dolomite CHAI Rukuan, LIU Yuetian, WANG Junqiang, XIN Jing, PI Jian, LI Changyong 2019, 36(4): 474-482.  DOI: 10.19596/j.cnki.1001-246x.7868 Abstract ( )   HTML ( )   PDF (23678KB) ( )   We studied adsorption characteristics of oil-water system on calcite and dolomite surface with molecular dynamic simulation. To study wettability of calcite/dolomite surfaces, we analyzed equilibrium conformation, relative concentration, radial distribution function and adsorption energy of calcite/dolomite-oil/water system. Then, we proposed a two-step adsorption mechanism. It shows that dolomite-oil/water system is more easily to achieve thermodynamic stability and is more stable; A water film is formed on calcite and dolomite surfaces, which is a double-layer structure; There are interactions among oil molecules, water molecules and the crystal surface; Attraction of dolomite surface to oil and water molecules is stronger than calcite. Finally, we divided the adsorption process into two steps:Water molecules adsorbed on crystal surfaces form a tightly adsorbed layer under van der Waals forces, electrostatic forces and O(CaCO3,CaMg(CO3)2)-H(H2O) hydrogen bonds. In addition, the remaining water molecules move to the crystal surface form a diffusion layer under the influence of O(H2O)-H(H2O) hydrogen bonds. It reveals wettability formation and alteration mechanisms on calcite and dolomite surface, which paves a foundation of further enhance oil reovery.

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Electrostatic Trap and Microtrap Arrays for Cold Polar Molecules on a Chip Surface WU Yan, LIU Siqi, LI Shengqiang 2019, 36(4): 483-490.  DOI: 10.19596/j.cnki.1001-246x.7880 Abstract ( )   HTML ( )   PDF (6571KB) ( )   An electrostatic surface trap for cold polar molecules with three charged poles is proposed. Distance between trap center and chip surface can be manipulated conveniently by altering voltages applied to the poles. Dynamic process of loading and trapping is simulated with classic method of Monte Carlo. It indicates that a loading efficiency of 40% for ND3 molecular beam with middle velocity of 11 m·s-1 is reached. Corresponding temperature of trapped molecules is about 25 mK. Our scheme can be further miniaturized and integrated to form one-dimensional and two-dimensional microtrap arrays which can be used in quantum computing and low-dimensional physics research.

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First-principles Study of Transition Metal Monoboride TMB QIN Ping, GAO Zhenbang, LIU Haidi, CHEN Yingcai 2019, 36(4): 491-497.  DOI: 10.19596/j.cnki.1001-246x.7860 Abstract ( )   HTML ( )   PDF (7724KB) ( )   We study thermodynamic stability, mechanical properties, and microscopic mechanisms of transition metal monoboride TMB (take TiB, VB and CrB in 3d series; ZrB, NbB and MoB in 4d series; HfB, TaB and WB in 5d series as examples) by first-principles calculations based on density functional theory and plane pseudopotential wave method. We found thermodynamic stability and hardness anomalies of transition metal monoborides. In particular, as valence electron concentration is 8 e·(f.u.)-1, thermodynamic stability is the most stable and hardness is the highest. To reveal its mechanism, we calculated electronic structure of TMB. As valence electron concentration of TMB is at 8 e·(f.u.)-1, covalent bonding of pd blocked effectively dislocation slipping between metal bilayers, prevented shear deformation, and resulted in high hardness. These discoveries may help new superhard material designs.

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Optimization of Synchronization Performance in Power Grids with Local Order Parameters ZOU Yanli, WANG Ruirui, WU Lingjie, YAO Fei, WANG Yang 2019, 36(4): 498-504.  DOI: 10.19596/j.cnki.1001-246x.7897 Abstract ( )   HTML ( )   PDF (5907KB) ( )   We use Kuramoto-like model as node model of power grids, and use local order parameters to describe local synchroniz ability. It shows that nodes with high power are difficult to locally synchronize to their direct neighbors. We propose a heterogeneous distribution method for network coupling strength. Keeping the total coupling strength, we increase coupling strength of links between high power nodes and their direct neighbor nodes, as well as links between other related nodes, and reduce coupling strength of links between the rest nodes. It shows that the method reduces critical synchronous coupling strength and improve synchronization performance in a certain range. As heterogeneity of the coupling strength is too great, synchronization performance of the network begins to deteriorate.