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25 January 2020, Volume 37 Issue 1 Previous Issue    Next Issue

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ALE Discontinuous Finite Element Method for One-dimensional Fluid Dynamics Equations with Chemical Reactions JI Meixuan, YU Xijun, SONG Mingyang 2020, 37(1): 1-9.  DOI: 10.19596/j.cnki.1001-246x.8005 Abstract ( )   HTML ( )   PDF (2433KB) ( )   A numerical simulation method for one-dimensional chemical reaction fluid mechanics equations is studied. Combining ideal gas state equation and using numerical flux of HLLC solution at boundary of each element, we present an ALE discontinuous finite element method. In high-order calculations, TVD slope limiter is used to suppress non-physical oscillation that may result from numerical solutions. Numerical results show that the algorithm maintains conservation and high precision of physical quantity. It captures clearly structural characteristics of detonation waves.

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Parallel Finite Element Algorithms Based on Two-grid Discretization for Time-dependent Navier-Stokes Equations DING Qi, SHANG Yueqiang 2020, 37(1): 10-18.  DOI: 10.19596/j.cnki.1001-246x.8000 Abstract ( )   HTML ( )   PDF (3081KB) ( )   Based on two-grid discretization and domain decomposition, three finite element parallel algorithms for unsteady Navier-Stokes equations are proposed. The key idea of the algorithms is to solve nonlinear problem firstly by Oseen iteration method on a coarse grid, and then to solve Oseen, Newton or Stokes problem in parallel on a fine grid to correct the coarse grid solution at each time step, respectively. Conforming finite element pairs are used for spatial discretization and backward Euler scheme for temporal discretization. Numerical results are shown to verify effectiveness of the algorithms.

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A Semi-Lagrangian Conservative Scheme for Vlasov Equation LIU Quan, NI Guoxi, NIU Xiao, HU Jun 2020, 37(1): 19-25.  DOI: 10.19596/j.cnki.1001-246x.7945 Abstract ( )   HTML ( )   PDF (13125KB) ( )   We give a semi-Lagrangian scheme for Vlasov-Poisson equation using third order upwind interpolation polynomial with limiter. The scheme is conservative and keeps solution positive. We use the scheme to compute typical examples that include Landau damping, two stream instability and symmetric two stream instability. These simulations are compared with other numerical results. In conclusion, the conservative scheme works well in solving Vlasov-Poisson equation.

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A Time Domain Dual Reciprocity Precise Integration Method for Scalar Wave Propagation Problems ZHOU Fenglin, WANG Weijia, LIAO Haiyang, LI Guang 2020, 37(1): 26-36.  DOI: 10.19596/j.cnki.1001-246x.8003 Abstract ( )   HTML ( )   PDF (4126KB) ( )   To avoid computation of multi-frequencies pressure in solution of frequency method, a dual reciprocity method (DRM) is applied to convert domain integral, which is related to derivatives of pressure over time, in boundary integral equation into boundary integral. Firstly, field points are collocated at all boundary nodes. With boundary condition, boundary quantities at boundary nodes can be represented linearly by quantities at domain nodes, which are applied for radial basis function interpolation and are arbitrarily distributed in DRM. Secondly, field points are further collocated at domain nodes. A system of ordinary differential equations (ODEs) of the second order is obtained. Thirdly, variation rate of pressure was introduced as an unknown quantity to reduce order of resulted ODEs. Finally, a precise integration method is adopted to solved the first ordered ODEs. Numerical examples demonstrated validity and stability of the method.

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Three-dimensional Numerical Simulation of Detonation Aftereffect of Suspended Aluminum Dusts in Corner Space YUE Junzheng, DONG Hefei, HONG Tao 2020, 37(1): 37-45.  DOI: 10.19596/j.cnki.1001-246x.8004 Abstract ( )   HTML ( )   PDF (13450KB) ( )   A three-dimensional two-phase detonation model for aluminum dusts/air mixtures is built. A 3D numerical simulation program for detonation of suspended Al dusts is developed with space-time conservation element and solution element (CE/SE) method. Moreover, program parallelization is realized based on message passing interface (MPI) technique. Reliability of the program is demonstrated with simulation of shock tube problem and two-phase detonation experiment of Al particles/air mixtures in a detonation tube. Two-phase detonation of 368 g·m-3 Al particles/air mixtures in left space of a corner and its aftereffect on air in the right and lower space of the corner are investigated. Propagation, reflection and diffraction of detonation wave or shock wave in complex space are obtained. It shows that air shock wave generated by two-phase detonation can reach a reflection pressure of 2.66 MPa at the solid wall 2 m far away from the Al dusts region. Fireball range exceeds initial Al dusts region by about 0.8 m. Air temperature within a range of 1.5 m near the initial Al dusts region is more than 1 600 K. The program can be used for aftereffect study of Al dusts detonation. It provides guidance for industrial safety and protection.

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DDES for Separated Transitional Flows Based on B-C Transition Model YU Qiuyang, BAO Yun, WANG Shengye, WANG Guangxue 2020, 37(1): 46-54.  DOI: 10.19596/j.cnki.1001-246x.8007 Abstract ( )   HTML ( )   PDF (4750KB) ( )   Empirical correlations in B-C transition model were calibrated with experimental values of zero pressure gradient plates. Calibrated B-C transition model predicts reasonably transition positions with low inlet turbulence intensity. However, due to limitations of RANS method, B-C transition model’s accuracy diminishes for massively separated flows. A turbulence closure named transitional Delayed Detached-Eddy Simulation (BC-DDES) method is proposed which combines traditional SA-DDES method and B-C transition model. This method has the potential for accurately capturing massively separated boundary layers in transitional Reynolds number range. Numerical simulation of three-dimensional S-K flat plate shows that BC-DDES method obtains transition prediction consistent with baseline transition model. Comparisons are evaluated on circular cylinder in crossflow. It shows that pressure distribution and drag coefficient of cylinder calculated with BC-DDES method agree well with experimental data, with less computational costs than tHRLES method.

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A Multi-component Mie-Grüneisen Mixture Model Based on HLLC Algorithm WU Zongduo, YAN Jin, ZONG Zhi, ZHAO Yong 2020, 37(1): 55-62.  DOI: 10.19596/j.cnki.1001-246x.7979 Abstract ( )   HTML ( )   PDF (4266KB) ( )   A revised robust HLLC(Harten-Lax-Van Leer-Contact) solver for multi-component Mie-Grüneisen mixture model is established. In Mie-Grüneisen mixture model, flux can be divided into conservative part and non-conservative part. Original HLLC scheme can well adapt to conservative part. As the original HLLC solver is directly extended to non-conservative part, oscillation is hard to be controlled. In original scheme, moving speed of discontinuous section refers to velocity at left or right side of the gird. It is replaced by average velocity within the grid. After the revision, the HLLC scheme is deduced again and extended to 2D problem. Numerical tests show that Mie-Grüneisen mixture model is robust and accurate with the help of modified HLLC solver.

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Coarse-grained MD Simulation of Nanopore Interaction Influence on Protein Translocation SHI Xiaorui, LIU Zhenyu, WU Huiying 2020, 37(1): 63-68.  DOI: 10.19596/j.cnki.1001-246x.7982 Abstract ( )   HTML ( )   PDF (5990KB) ( )   Effect of nanopore-water/nanopore-protein interaction on electrophoresis mobility of protein translocation is studied with coarse-grained molecular dynamics simulation. With steer molecular dynamics, friction coefficient and friction of protein under different interactions are analyzed. It shows that protein adhesion to nanopore wall has weak effect on protein translocation through a nanopore, while nanopore-water interaction has significant effect on electrophoretic mobility and friction coefficient. The increase of interaction between nanopore and water increases difference between movement of water molecules near nanopore wall and protein, which leads to increase of friction coefficient of protein translocation. As a result, mobility electrophoresis of protein through nanopore is affected. It provides a theoretical guidance for the design of nanopore materials.

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Transient Behavior Analysis of Fractured Horizontal Wells Based on an Improved Green Element Method FANG Sidong, WANG Weihong, WU Yonghui, CHENG Linsong 2020, 37(1): 69-78.  DOI: 10.19596/j.cnki.1001-246x.7977 Abstract ( )   HTML ( )   PDF (8864KB) ( )   We proposed a modified Green element method based on edge-based element concept. Unknowns and matrix dimension are reduced. Then, a local grid refinement method is proposed based on the improved Green element, which ensures precision in early flow regimes for fractured horizontal wells with complex fractured networks. Solution of a degradation model solved with the method is compared with solutions obtained with a semianalytical model and numerical simulation. It verifies accuracy and efficiency of the improved Green element method based on local grid refinement. Finally, effects of model parameters on transient behavior is analyzed. It shows that the Green element method is a high precision dynamic simulation method, which improves computational efficiency of dynamic simulation of fractured horizontal well by setting node on edge of grid. In addition, local grid refinement method applied to the modified Green element method is based on superposition principle, in which interpolation approximation is not needed. The method is of high accuracy. Under same grid systems, local grid refinement based on improved Green element method is better than using finite difference. On the other hand, conductivity of complex fracture, permeability and size of stimulated reservoir volume have great influence on transient behavior of fractured horizontal wells. These effects should be taken into consideration and interpreted in transient behavior analysis.

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Numerical Study of Droplet Impact Liquid Film with MRT-LB Pseudo-potential Model LIAN Xiaolong, CHEN Yue, LI Peisheng, ZHANG Ying, LI Wei, LIU Qiang 2020, 37(1): 79-87.  DOI: 10.19596/j.cnki.1001-246x.7985 Abstract ( )   HTML ( )   PDF (7537KB) ( )   An improved LB pseudo-potential multi-relaxation multiphase model is used to study flow characteristics of single/dual droplets impacting liquid film. Development of liquid film impacted by a single droplet under different gas-liquid density ratio was investigated. It was found that with decrease of density ratio, top of coronal crown started bending inward, and bottom radius is significantly reduced. Then, double droplets impinging on liquid film was studied with large density ratio. It shows that a central jet was generated as double droplets impacting on liquid film. Increase of horizontal spacing between droplets delaied the appearance of central jet and reduced height of the initial central jet. With the increase of Re, height of the central jet increased obviously.

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Near-field Ferromagnetic Object Detection Based on 3D Magnetic Imaging LI Jian, JIN Chunxing, ZHANG Yu, HUANG Xinjing 2020, 37(1): 88-96.  DOI: 10.19596/j.cnki.1001-246x.7966 Abstract ( )   HTML ( )   PDF (15631KB) ( )   We propose a method for three-dimensional inversion imaging of unknown magnetic sources in near-field conditions. Considering that most magnetic sources are not only magnetized with background magnetic field, but also have strong remanence, we convert magnetic field on observation surface into magnetic field vector anomaly modulus, and establish objective function to optimize solution to get the best match for magnetic field characteristics. Simulations and experiments show that the method eliminates effectively influence of residual magnetism on inversion results, and realizes imaging of magnetic susceptibility distribution of multiple magnetic sources in near field. It shows that the proposed method can be used to detect position and shape of unknown magnetic body.

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Fast Simulation of Radiation Near-fields of Large Vertically Polarized EMP Radiating-wave Simulator ZHU Xiangqin, WU Wei, JIA Wei, CAI Libing 2020, 37(1): 97-106.  DOI: 10.19596/j.cnki.1001-246x.7981 Abstract ( )   HTML ( )   PDF (7297KB) ( )   A hybrid parallel technology on message-passing interface (MPI) platform in axisymmetric cylindrical coordinates, combining parallel finite-difference time-domain(FDTD) method and near- to near-field transformation with Kirchhoff surface integral representation(KSIR), is presented for fast computing radiation fields of large vertically polarized EMP radiating-wave simulator. Transient response of electric field at testing points as the simulator excited by double exponential function is given. Calculation results are consistent with those by software and parallel FDTD method, while the computing time is saved about 80%. Speedup factor and efficiency of hybrid parallel technology are measured. The hybrid method has advantages of saving computing time and CPU storage especially for larger simulators. Radiation far-fields besides near-fields in time-domain of simulator can be obtained as well.

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Analysis and Treatment on Structures with Temperature Cross in Heat Exchanger Network SU Geman, CUI Guomin, BAO Zhongkai, XIAO Yuan, CEN Zhenyu 2020, 37(1): 107-118.  DOI: 10.19596/j.cnki.1001-246x.7993 Abstract ( )   HTML ( )   PDF (7212KB) ( )   As heat exchange loads are treated as continuous variables to be optimized in heat exchanger network (HEN) problems, temperature cross could be generated in stream matches. Infeasible structures with temperature cross are penalized by penalty function method in literature. However, in random walk algorithm with compulsive evolution (RWCE) algorithm to HEN optimization, structures with temperature cross may be accepted as imperfect solutions due to its mutation operation of accepting imperfect solutions, which may negatively affect optimization process and decrease algorithm efficiency. Hence, temperature cross in HEN is firstly explained. Then negative effects of infeasible structures on optimization process of RWCE is described. A treatment method is proposed: Individuals trapped in infeasible regions are compulsively returned to their original positions in feasible regions to accept re-optimization. It was demonstrated that the proposed method improves algorithm efficiency and achieves better results than reported ones in literature.

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Effect of Strain on Electronic Structure and Optical Properties of Wurtzite GaN WEN Shumin, YAO Shiwei, ZHAO Chunwang, WANG Xijun, LI Jijun 2020, 37(1): 119-126.  DOI: 10.19596/j.cnki.1001-246x.7972 Abstract ( )   HTML ( )   PDF (19098KB) ( )   Effects of strain on electronic structure and optical properties of wurtzite GaN are studied by using generalized gradient approximation (GGA+U) under first-principles density functional theory (DFT). It shows that the bandgap decreases with increase of strain. The decrease of band gap is small as compressive strain is less than 3%. Strain has an effect on dielectric function imaginary part. With increase of strain, static dielectric constant increases and absorption coefficient decreases.