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25 May 2021, Volume 38 Issue 3 Previous Issue    Next Issue
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Interview archives: The world as I see it Jie LIU, Shuo HUANG, Wenjuan LYU, Ying YUE 2021, 38(3): 253-256.  Abstract ( )   HTML ( )   PDF (2903KB) ( )

Research Reports

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A Multi-material Five-equation-reduced Model and Artificial Compression Method for Interface Capture Chuang XUE, Xingdong LI, Wenjun SUN, Wenhua YE, Xianjue PENG 2021, 38(3): 257-268.  DOI: 10.19596/j.cnki.1001-246x.8248 Abstract ( )   HTML ( )   PDF (8825KB) ( )   The volume fraction equations of five-equation-reduced model were studied and numerical scheme was developed in two-dimensional Eulerian frame in planar and cylindrical geometry. To capture material interfaces, Yang's slope modification of artificial compression method was adopted in MUSCL, PPM and WENO type data reconstruction processes. HLLC-HLLCM hybrid flux was applied in Godunov type scheme to avoid numerical shock instability. For multi-material Riemann problems, numerical results show that the scheme captures shock and contact discontinuities with non-oscillatory character. No numerical shock instabilities growing shows as small perturbations was adding on initial physical variables. SOD problems in cylindrical and spherical geometries and contact-type two-dimensional Riemann problem were studied.

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A Monolithic Preconditioned Iterative Solver and Parallel Computing for Three-dimensional Thermal Radiation Transport Equation Lingxiao LI, Chuanlei ZHAI, Hui XIE, Yi SHI 2021, 38(3): 269-279.  DOI: 10.19596/j.cnki.1001-246x.8238 Abstract ( )   HTML ( )   PDF (8862KB) ( )   We present a monolithic preconditioned iterative solver for implicit discrete ordinate equations of three-dimensional grey thermal radiation transport and parallel codes are developed. A strategy of assembling linear algebraic systems is used to obtain radiation intensity in all discrete directions simultaneously. With preconditioned Krylov subspace iterative methods, the solver avoids possible mesh cycles in complex grids associated with sweep algorithms, which improves robustness and computational efficiency. First order upwind finite volume scheme is used for space discretization. Numerical experiments verify convergence rate on distorted hexahedral grids and assess performance of preconditioned iterative methods. Problems with coupled radiation and matter are simulated. Simulation results of three-dimensional crooked pipe and hohlraum problems are shown. It shows validity of the codes and flexibility of the method.

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Raising of Particles on a Wall Behind a Normal Shock Wave Perpendicular to the Wall Shesheng XUE, Shouxian LI 2021, 38(3): 280-288.  DOI: 10.19596/j.cnki.1001-246x.8242 Abstract ( )   HTML ( )   PDF (3306KB) ( )   To reveal shock wave entrainment of particles on a wall, simulation is carried out for raising of single particle on a wall behind a shock wave perpendicular to the wall. The particle is assumed air-born(depart from the wall immediately) at initial time, and is acted by gravity, gas resistance, and Saffman force. The model equation is a combination of boundary layer equations of gases behind shock wave and ordinary differential equations describing movement of the particle. A single parameter method and a 4-order Rung-Kutta method are employed to solve boundary layer equations and particle movement equations, respectively. Calculated particle velocities and their tracks show that the basic dynamic of particle entraining is from Saffman force provided by strong shear flows in boundary layer. The raising height of particle is independent of intensity of the shock wave. It changes with size of the particle. Calculated results agree with experimental results in references. It validates the model and the assumptions.

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Numerical Simulation of Bubble Dynamics in Porous Media with a Lattice Boltzmann Large Density Ratio Model Qin LOU, Sheng TANG, Haoyuan WANG 2021, 38(3): 289-300.  DOI: 10.19596/j.cnki.1001-246x.8264 Abstract ( )   HTML ( )   PDF (5527KB) ( )   With a lattice Boltzmann two-phase flow model with large density ratio, we study dynamic behavior of a bubble as it passes through a porous media. It was found that as the porosity is large, the bubble deforms without breaking, and it passes completely through the porous medium; As the porosity is small, the bubble deforms violently and ruptures, and it takes more time to pass through the porous medium. In addition, as the contact angle of the porous medium is small, the bubble passes completely through the porous medium; As the contact angle increases, the bubble begins to rupture; The larger the contact angle is, the more seriously the bubble ruptures. The residual mass of the bubble decreases with the increasing of the contact angle. Moreover, it shows that as Eotvos number (Eo) increases, the proportion of surface tension decreases; The bubble ruptures more seriously; And the residual mass of the bubble passing through the porous media is smaller. It is found that the influence of wettability on residual mass of the bubble is the most obvious, and the influence of Eo is the minimum.

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Numerical Study on Natural Convective Flow and Heat Transfer of Nanofluids in a Circular Tube Containing Heat Source with Different Shape Guyue TANG, Qin LOU, Haoyuan WANG 2021, 38(3): 301-312.  DOI: 10.19596/j.cnki.1001-246x.8244 Abstract ( )   HTML ( )   PDF (9538KB) ( )   Natural convection of copper(Cu)-water nanofluids in a circular tube containing heat source with different shape (circular, triangular, and square) is numerically simulated with lattice Boltzmann method. Effects of Rayleigh number, nanoparticle volume fraction, and geometric shape of heat source on flow and heat transfer characteristics of the nanofluid are studied. It shows that heat transfer can be enhanced with increasing volume fraction of nanoparticles. And the increase of average Nusselt number in the case with small Rayleigh numbers is faster than those with large Rayleigh numbers. The largest average Nusselt number could be obtained in the square heat source case for all Rayleigh numbers considered. Finally, empirical prediction functions among average Nusselt number of the heat source surface, volume fraction of nanoparticles, and the Rayleigh number are presented. These relations provide predictions for engineering problems.

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Lattice Boltzmann Study of a Droplet Impinging on a Stationary Droplet on a Fixed Wall Surface with Different Wettability Jia LIANG, Ming GAO, Lu CHEN, Dongmin WANG, Lixin ZHANG 2021, 38(3): 313-323.  DOI: 10.19596/j.cnki.1001-246x.8265 Abstract ( )   HTML ( )   PDF (8601KB) ( )   A single-component multi-phase pseudo-potential lattice Boltzmann method is used to simulate the process of a large droplet vertically hitting a stationary small droplet on a wall with different wettability. The size ratio of the droplets is 1.5. Hydrophilic and superhydrophobic wall surfaces are studied. The droplet spreading factor and relative height are obtained. It shows that as We number increases the spreading factor of the droplet increases, the spreading diameter increases and the relative height reduces. And as We number increases, on a superhydrophobic surface, a cavity appears at the bottom of the spreading process and size of the cavity increases. In addition, as We number increases to 107.35 the droplet breaks.

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Applicability Exploration of Superposition Principle for Pressure Transient Analysis in Polymer-flooding System Jia ZHANG, Shiqing CHENG, Yang ZENG, Man ZHANG, Haiyang YU 2021, 38(3): 324-332.  DOI: 10.19596/j.cnki.1001-246x.8262 Abstract ( )   HTML ( )   PDF (1797KB) ( )   A mathematical model for pressure transient analysis in polymer-flooding system was established, in which the shear thinning effect of non-Newtonian polymer solution is considered. The governing equations were discretized by finite volume method with a hybrid grid consisting of Cartesian meshes with radial refinement around well positions. The shut-in pressures from numerical solution were compared with those obtained with the superposition principle method. It shows that shut-in bottom-hole pressure computed with superposition principle method is much lower than the numerical result for polymer-flooding system, which indicating that the superposition principle cannot be used for pressure transient analysis in polymer-flooding system. Shut-in pressure data of an injection well in a polymer-flooding system was interpreted. It is found that the permeability obtained with superposition principle method is very small, which shows that the superposition principle method cannot be used to solve the nonlinear model for pressure transient analysis in polymer-flooding system. The numerical method is more suitable for polymer-flooding system. The conclusions are applicable to similar nonlinear problems in pressure transient analysis.

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An RWCE Algorithm with Intelligently Adjusted Acceptance Probability of Improper Solutions Yiwen JIANG, Guomin CUI, Zihe CHEN, Jiaming YU, Qianqian ZHAO 2021, 38(3): 333-342.  DOI: 10.19596/j.cnki.1001-246x.8214 Abstract ( )   HTML ( )   PDF (2253KB) ( )   Random walk algorithm with compulsive evolution(RWCE) is an effective method for the optimization of heat exchanger network with advantage of simple evolutionary strategy and less control parameters. The probability of accepting improper solution has important influence on individual jumping out of local optimal solution. We count times of total annual cost decrease in a certain iteration interval in the later stage of optimization, and analyze influence of probability of accepting improper solution in the optimization process. A heat exchange network optimization method is proposed to adjust probability of accepting improper solution with difference between structure of improper solution and original structure. It strengthens evolutionary ability of the algorithm. Effectiveness of the strategy is shown with several examples.

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Effect of Shear Flow on Secondary Magnetic Islands in DTM at High Magnetic Reynolds Numbers Yao TAN 2021, 38(3): 343-351.  DOI: 10.19596/j.cnki.1001-246x.8235 Abstract ( )   HTML ( )   PDF (16043KB) ( )   At high magnetic Reynolds numbers, as double tearing modes develop into rapid magnetic reconnection phase secondary magnetic island instability occurs, which intensifies the release of magnetic field energy. We developed a high-precision numerical simulation program based on perturbed conservative MHD equation. Effect of antisymmetric shear flow on second-order magnetic islands in double tearing modes was studied in a plane configuration. It shows that the number of secondary magnetic islands and current-sheet aspect ratio both decrease with the increase of shear flow velocity and gradient of shear flow velocity. In addition, a strong polar shear flow inhibits the occurrence of secondary magnetic island instability.

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Terminating Arrhythmia by Using Motion Controller Jing BAI, Zhijing HUANG, Guoning TANG 2021, 38(3): 352-360.  DOI: 10.19596/j.cnki.1001-246x.8243 Abstract ( )   HTML ( )   PDF (7965KB) ( )   A control method suppressing spiral wave and spatiotemporal chaos by using local electric shock produced by moving controller is proposed. The local electric shock is to myocardial cells around spiral wave tip to suppress the rotation of spiral wave tip, causing spiral wave tip to move out of the boundary. We studied numerically with Luo-Rudy phase I heart model. It shows that with appropriate number of grid points controlled by local electrical shock and the control thresholds of membrane potential, both spiral wave and spatiotemporal chaos can be suppressed. The minimum number of controlled grid points is 9. The shortest control times of spiral wave and spatiotemporal chaos are less than 150 ms and 500 ms, respectively.

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Dynamics Modeling of Charged Defects in Si under B Ion Implantation Pengdi LI, Jun LIU, Qirong ZHENG, Chuanguo ZHANG, Yonggang LI, Yongsheng ZHANG, Gaofeng ZHAO, Zhi ZENG 2021, 38(3): 361-370.  DOI: 10.19596/j.cnki.1001-246x.8245 Abstract ( )   HTML ( )   PDF (2331KB) ( )   To describe accurately the dynamic physical process and obtain quantitatively boron (B) spatial distribution as well as it's evolution behaviors in silicon (Si) under boron implantation, we built a multiscale dynamic model of charged defects. In the model, multiple microscopic processes of defects generation and evolution are comprehensively considered under B ion implantation, including charge states of defects and reactions among charged defects, evolution of B-interstitial clusters (BICs) and interactions between charged defects and carriers. The simulated B distribution is consistent with experiments. It shows that BICs dominate the depth distribution of B concentration and interstitial B (BI) makes B distribution extend into depth. Besides, considering charge states of defects, we correct diffusion coefficients of Si interstitials (I) and BI so that the behavior of B distribution can be described accurately. The model reveals real physical processes and micro-mechanisms in Si under B implantation, which demonstrates that BICs and real charge states of defects are the key in describing B distribution. It provides theoretical guidance for semiconductor device fabrication.

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Enhanced Photocatalytic Activity of ZnO for Water-splitting with Isovalent Anion-Cation Codoping: First-principles Calculations Jing PAN, Guohua SHEN 2021, 38(3): 371-378.  DOI: 10.19596/j.cnki.1001-246x.8253 Abstract ( )   HTML ( )   PDF (6187KB) ( )   We propose an isovalent anion-cation codoping approach to improve photoelectrochemical (PEC) water-splitting efficiency of ZnO for hydrogen production. First-principles calculations reveal that the isovalent codoping reduces the band gap to enhance optical absorption in visible light and suppresses electron-hole recombination centers to improve carrier mobility as well. Specifically, (Cd+Te) codoped ZnO may be a strong candidate for PEC water-splitting in virtue of its suitable band gap and matched band edge positions for water redox. This isovalent codoping approach could be applied in other wide-band-gap semiconductors for improving photocatalytic activity.