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25 March 2020, Volume 37 Issue 2 Previous Issue    Next Issue

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An Arbitrary Lagrangian-Eulerian Type Moving Mesh Generalized Riemann Problem Scheme for Reactive Flows XIAO Min, XU Xihua, NI Guoxi 2020, 37(2): 127-139.  DOI: 10.19596/j.cnki.1001-246x.8019 Abstract ( )   HTML ( )   PDF (7253KB) ( )   We present a generalized Riemann problem based, remapping free moving mesh scheme to simulate reactive flows. The scheme is based on solution of a generalized Riemann problem on moving meshes and is explicitly remapping free. In construction of numerical fluxes, we use generalized Riemann problem scheme to get high accuracy. A variational approach is applied to generate an adaptive moving mesh to get high resolution in reactive zone. The scheme can not only keep the mesh quality,but also avoid efficiently numerical errors induced by an explicit remapping process in arbitrary Lagrangian-Eulerian methods. Numerical experiments, including Chapmann-Jouguet detonation and unstable detonation, demonstrate accuracy and robustness of the scheme. It shows that the generalized Riemann problem moving mesh method performs well for reactive flows with both discontinuities and smooth structures.

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An ADRS Approximated Riemann Solver in Compatible Lagrangian Method LIU Yan, MAO Dekang 2020, 37(2): 140-152.  DOI: 10.19596/j.cnki.1001-246x.8031 Abstract ( )   HTML ( )   PDF (33795KB) ( )   Analyzing advantages and disadvantages of three Riemann solvers of AC(Acoustic), MFCAV(Multi Fluid Channel on Averaged Volume) and HLLC for compressible multimaiterial fluid problems, we constructed an adaptive Riemann solver(ADRS) as a weighted average of three solvers. Rule for designing weights is discussed in detail. ADRS Riemann solver is applied to a compatible cell-centered Lagrangian method which resisting spurious mesh deformation by viewing MFCAV as a modification of AC solver. Numerical examples include Taylor Green vortex problem are given to show efficiency of the method.

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A Fast Filtered-Back-Projection Algorithm for Image Reconstruction of Compton Camera YAN Xiaosong, YANG Jianlun, YANG Yiwei 2020, 37(2): 153-162.  DOI: 10.19596/j.cnki.1001-246x.8037 Abstract ( )   HTML ( )   PDF (7890KB) ( )   A Compton camera consisting of a CZT pixel detector and a NaI scintillator array was proposed. Factors that affect angular resolution of the camera, including geometry of detectors, energy resolution and Doppler effect of CZT detector, were analyzed. Overall angular resolution was between 5.1° and 5.6° and geometry of detectors was confirmed as main factor that limits angular resolution of the camera. A filtered-back projection algorithm was analytically deduced. The angular resolution was 1.7° as broadening was omitted, and 4.2° as broadening was considered. Geant4 simulations were performed and the data were reconstructed with a practical method of filtered-back projection algorithm. Angular resolution was 1.7° as broadening was omitted and 5.1° as practical broadening factors of Compton camera was considered. Parallel acceleration with GPU in the framework of OpenCL was applied in the reconstruction and the acceleration ratio was 79.

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An Open Boundary Condition with Application in Internal Tide Simulation MIAO Chunbao, WU Lidan 2020, 37(2): 163-172.  DOI: 10.19596/j.cnki.1001-246x.8014 Abstract ( )   HTML ( )   PDF (6040KB) ( )   A clamped radiation boundary condition is proposed. Clamped radiation condition can be used as both active and passive open boundary conditions (OBCs), and can be used in simulating tides and other oceanic dynamic processes. Several OBCs were compared in a layered internal tide model with mode-split technique. In external mode, Dirchlet condition, clamped radiation condition, Flather condition and relaxation condition were compared. It shows that performance of clamped radiation condition and Flather condition is the best, but clamped radiation needs less data than Flather contidion, and hence can be applied more widely. In internal mode, relaxation condition, Sommerfeld radiation condition and Sommerfeld radiation condition based on normal mode were compared. It shows that relaxation condition is the best.

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Steady Heat Conduction Analysis of Functionally Graded Materials with Barycentric Lagrange Interpolation Collocation Method WANG Leilei, JI Le, MA Wentao 2020, 37(2): 173-181.  DOI: 10.19596/j.cnki.1001-246x.8024 Abstract ( )   HTML ( )   PDF (3809KB) ( )   A new meshless method, named collocation method with barycentric Lagrange interpolation (BLIC), is presented for analyzing steady-state heat conduction in two-dimensional functionally graded materials(FGMs). Two-variable barycentric Lagrange interpolation function and its partial derivatives at Chebyshev nodes are derived. Then, based on a collocation method, it is directly introduced into controlling equations and boundary conditions of GEMs to obtain a linear discretijed equation. The method is a truly meshless method and takes advantages of both barycentric Lagrange interpolation and collocation method such as low computational cost, stable, accurate and easy to numerical implementation. Temperature fields of exponential, quadratic and trigonometrical FGMs models are simulated. It shows that the method is accurate and efficient, and is not sensitive to the change of material gradient parameters. It can be extended to solve transient heat conduction and thermal stress analysis of FGMs.

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Entropy Generation Analysis for Grooved Structure Plate Flows LIU Mei, LI Shuguang, WU Zhengren, WANG Songling, DENG Yuhan 2020, 37(2): 182-188.  DOI: 10.19596/j.cnki.1001-246x.8021 Abstract ( )   HTML ( )   PDF (13757KB) ( )   To investigate entropy generation caused by a grooved structure on flow, we used Fluent software and large eddy simulation (LES) technology to analyze entropy generation in flow over a plate with a grooved structure. It showed that a grooved structure was able to reduce entropy generation in the flow. At 30 m·s-1(Re≈20 000), total entropy generation in near-wall region decreased by approximately 25%. And at 40 m·s-1(Re≈27 000), it decreased by approximately 19%. However, the grooved structure did not have a sustained effect on subsequent flow. As distance from the wall in the normal direction increased, the effect decreased gradually. Entropy production at the top of the trench is much greater. And entropy production caused by turbulence is dominant. It provides a theoretical basis for optimizing drag reduction of trench structures.

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An Interpretation Method with “Well-Cave-Crack” Model of Dissolves Reservoir Considering Gravity Factors XU Yandong 2020, 37(2): 189-197.  DOI: 10.19596/j.cnki.1001-246x.8032 Abstract ( )   HTML ( )   PDF (3305KB) ( )   Shunbei oilfield belongs to fault reservoir formed by movement of large fracture structures. Longitudinal fracture system and vertical distribution of caves are main storage collective spaces. It is proposed that the pressure change in a cavern is caused by flow and fluctuation. According to this, energy conservation equation is combined with well test theory, and a method is established to explain well test of dissolvable reservoir considering gravity factors. With dimensionless quantity and Laplace transformation of dimensionless equation, bottom pressure on Laplace space is obtained. Plate curve for well test analysis is obtained with Stehfest numerical inversion algorithm. Sensitivity analysis of gravity factors shows that gravity factors affect end of the double logarithmic curve. As gravity factors are obvious, curve characteristics are similar to fixed pressure boundary. A well in Xinjiang oilfield is analyzed, in which the reason why it fell down in the later stage of the curve is explained and the valume of karst cave and other related parameters are given. The results are consistent with actual production situation.

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Multiple Screw Parallel Dislocations and a Griffith Crack in Magnetoelectroelastic Body GUO Huaimin, ZHAO Guozhong 2020, 37(2): 198-204.  DOI: 10.19596/j.cnki.1001-246x.8016 Abstract ( )   HTML ( )   PDF (1616KB) ( )   Interactions among parallel screw dislocations and a Griffith crack in magnetoelectroelastic media are investigated in terms of fundamental equations. Combining Muskhelishvili techniques and operator theory, analytic solutions for stress fields, electric fields and magnetic fields induced by screw dislocation and crack in magnetoelectroelastic solid are derived. Numerical examples show that singularity of stress occurs at crack tip and dislocation core. Away from dislocation point, the generalized stress is smaller, which is verified with existing results. As dislocation point approaches crack tip, stress fields between crack and dislocation tends to zero.

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Atomistic Analysis of Myoglobin Mechanical Unfolding HE Erbin, LUO Zhirong, ZHU Liuhua 2020, 37(2): 205-211.  DOI: 10.19596/j.cnki.1001-246x.8009 Abstract ( )   HTML ( )   PDF (9473KB) ( )   Myoglobin, which exists widely in skeletal muscle of vertebrates, plays crucial roles in life processes. Its proper folding depends on the binding of heme. In this paper, we report an atomistic and statistical analysis of force-induced unfolding of myoglobin with and without heme binding. It shows that heme is responsible for not only its biological functions, but also its unfolding dynamics. The unfolding pathway of myoglobin without heme binding involve an intermediate configuration. More importantly, it shows that intermediate state in force-induced unfolding process is different from that in chemical denaturant, which leads to the discovery of new intermediate configurations. Our results are in good agreement with related experimental observations and provide significant insight into general mechanisms of myoglobin unfolding.

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Molecular Dynamics Simulation on Crystallization Kinetics of Sodium Sulfate in Supercritical Water ZHOU Lu, MA Honghe 2020, 37(2): 212-220.  DOI: 10.19596/j.cnki.1001-246x.8012 Abstract ( )   HTML ( )   PDF (8168KB) ( )   Sodium sulfate is a common inorganic salt that causes blockage in supercritical water (SCW) reactors. An investigation of its crystallization kinetics is important for the design of deposition-preventing reactors. Microscopic crystallization process of sodium sulfate in SCW was studied with LAMMPS molecular dynamics simulation. Water molecule was calculated with SPC/E model, and ion-ion and ion-water interactions were calculated with Coulumb and Lennard-Jones combined potential energy functions. It shows that the impact of water on electrostatic shielding effect of ion charges decreases at higher temperatures and lower densities. Increasing temperature and density is advantageous to diffusion of ions, which helps ions to collide and form nuclei. Magnitude of nucleation rate is generally in the order of 1029 cm-3s-1 in simulated parameters range of SCW.

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Adsorption Mechanism of Two Organic Molecules with Different Polarities on Calcite (104) Surface: Density Functional Theory Study CHAI Rukuan, LIU Yuetian, YANG Li, ZHANG Yixin, XIN Jing, MA Jing 2020, 37(2): 221-230.  DOI: 10.19596/j.cnki.1001-246x.8027 Abstract ( )   HTML ( )   PDF (11446KB) ( )   Density functional theory was employed to explore adsorption mechanism of benzoic acid and toluene molecules on calcite surface, and to analyze influence of polarity on the adsorption. It showed that benzoic acid was tilted adsorbed on CaCO3(104) surface in the form of undissociated molecules and in monodentate mode, while toluene was parallel adsorbed. Geometrical structure of organic molecules changed significantly during the adsorption, in which the deformation of benzoic acid was much greater than that of toluene. Meanwhile, electronic structure of the adsorption system was also changed. During the adsorption of benzoic acid, Ca-O ionic bond and H-O covalent bond were formed. However, there was only weak hydrogen bond between toluene and CaCO3(104) surface. Obviously, adsorption intensity of benzoic acid (polar molecule) on CaCO3(104) surface is greater than that of toluene (non-polar molecule). It provided theoretical support for EOR and mineral flotation engineering.

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Effect of Hydrostatic Pressure on Magneto-optical Properties of Al14Mn2P16: A Density Functional Theory Study CHEN Yu, XING Yongming 2020, 37(2): 231-239.  DOI: 10.19596/j.cnki.1001-246x.8023 Abstract ( )   HTML ( )   PDF (13851KB) ( )   With first-principle calculations, we investigate elastic and magneto-optical properties of Al14Mn2P16 under hydrostatic pressures (0~20 GPa). Our calculations show that the ground state is a ferromagnetic state. The system was proved stable according to the elastic stability criterion. The magnetic moment decreases with increasing hydrostatic pressure. Below 5 GPa, the system hosts Curie temperature (TC) of 184 K combine with a slightly decrease with increasing hydrostatic pressure. Furthermore, intriguingly, as external pressure furthers improves, TC drops sharply, even vanishes at 18 GPa. It was found that the absorption peak in visible optical range has obvious blue shift. As hydrostatic pressure reaches 20 GPa, absorption peak in visible optical range disappears.

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Synchronization Control and Parameter Identification for Unified Chaotic System Based on Improved Clonal Selection Algorithm SHI Jianping, LI Peisheng, LIU Guoping 2020, 37(2): 240-252.  DOI: 10.19596/j.cnki.1001-246x.8001 Abstract ( )   HTML ( )   PDF (11947KB) ( )   An improved clonal selection algorithm was proposed for parameter identification of chaotic systems. Global exploration and local exploration of the algorithm are effectively balanced by two mechanisms of hypermutation and receptor editing. Convergence quality of the algorithm is improved by introducing strategy of learning from elite antibody. Experiments on 10 optimization problems show that the algorithm has good performance in terms of accuracy, convergence speed and stability. Taking synchronization control of unified chaotic system with unknown parameter as research object, synchronization controller was designed reasonably and stability of the synchronization system was analyzed theoretically. By setting synchronization scale factors, a variety of synchronization methods such as complete synchronization, anti-synchronization and projective synchronization of unified chaotic system are realized. Simulation results show that the method realizes accurate identification of unknown system parameter and effective synchronization control of drive-response system. Feasibility and effectiveness of the method are verified.