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25 November 2020, Volume 37 Issue 6 Previous Issue    Next Issue

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Influence of Capsule Support Tent on ICF Capsule Implosion Performance: Simulation Study GU Jianfa, GE Fengjun, DAI Zhensheng, ZOU Shiyang 2020, 37(6): 631-638.  DOI: 10.19596/j.cnki.1001-246x.8167 Abstract ( )   HTML ( )   PDF (9065KB) ( )   Influence of capsule support tent on ICF DD gas implosion performance is investigated with a two-dimensional radiation diffusion hydrodynamic code LARED-S. It shows that the support tent reduces significantly the neutron yield with a YOC (yield over clean) of 55.2%. The main degradation mechanism is that the capsule shell produces high-amplitude high-density spikes, penetrating deep into the central DD gas. It increases greatly power loss due to electron conduction on the CH/DD interface, leading to the rapid reduction of DD reaction rate and final neutron yield. Compared with one-dimensional ideal implosion simulation result, bang-time of the two-dimensional tent simulation is apparently earlier, and perturbations introduced by the capsule support tent reduce the central pressure and internal energy of DD gas, which is converted from the shell implosion kinetic energy.

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Application of Adaptive Multi-resolution Method in Numerical Simulation of Reactive Multiphase Flows NIU Xiao, NI Guoxi, MA Wenhua 2020, 37(6): 639-652.  DOI: 10.19596/j.cnki.1001-246x.8176 Abstract ( )   HTML ( )   PDF (9372KB) ( )   We applie adaptive multi-resolution method to numerical simulation of stiffened-gas equation of state based on CJ model. A conservation sharp interface method of multiphase flow, in which the interface problem is tracked and solved by level-set method and ghost fluid method, is adopted. This method handles long physical time scale interactions across interface well and reduces conservative associated errors. In addition, pyramid data structure and adaptive multi-resolution analysis are used to improve storage efficiency and calculation efficiency of the algorithm. Finally, numerical examples are given to demonstrate stability and effectiveness of the adaptive multi-resolution method in numerical simulation of reactive multiphase flows.

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A Well-balanced Gas Kinetic Scheme ZOU Xing, CHEN Songze, GUO Zhaoli 2020, 37(6): 653-666.  DOI: 10.19596/j.cnki.1001-246x.8158 Abstract ( )   HTML ( )   PDF (10674KB) ( )   Hydrostatic equilibrium is a static state that the fluid pressure is balanced with gravity. Classic finite difference and finite volume methods cannot maintain this equilibrium state on discrete scales, and produce non-physical phenomena often such as spurious currents. In this work, volume integral of the source term is implemented at cell interface, so that the balance of pressure and gravity under discrete conditions is achieved on discrete scales. A well-balanced gas kinetic scheme of the Navier-Stokes(NS) equation is therefore constructed. The scheme maintains accurately the static equilibrium state under isothermal conditions and captures small perturbation propagation near equilibrium state at machine precision. At the same time, the scheme solves non-isothermal stratified flow near equilibrium state. Apart from the non-isothermal equilibrium described by Euler's equation, the scheme can also represent balance of thermal conduction in addition to force balance. It is shown that the scheme preserves second-order accuracy with respect to both density and temperature distribution when simulating an non-isothermal equilibrium state. Numerical examples reveal that the scheme is a potential tool in simulating stratified flow of temperature and density under gravitational field.

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Ruelle-Takens Chaotic Natural Convection in a Horizontal Annulus with an Internally Slotted Circle ZHAO Ming, WANG Ke, YU Duanmin 2020, 37(6): 667-676.  DOI: 10.19596/j.cnki.1001-246x.8159 Abstract ( )   HTML ( )   PDF (2216KB) ( )   Natural convection in a two-dimensional horizontal annulus with an internally slotted circle is analyzed with lattice Boltzmann method (LBM). Flow instability is studied with nonlinear dynamic analysis techniques such as phase diagram and power spectrum. It shows that, with the increase of Rayleigh number Ra, the flow field changes from the beginning of a stable equilibrium point to a limit cycle after Hopf bifurcation. And the flow field may exhibit a change from steady-state to periodic oscillation. As the Rayleigh number is further increased, the stable limit cycle change to a two-dimensional torus. As the Rayleigh number Ra is greater than a critical value, chaotic state appears, and the system has a very complicated trajectory structure in the phase space. In general, the nonlinear dynamic characteristics and expressions at different Rayleigh numbers in the system show that the system evolves to chaos through Ruelle-Takens road. It shows evolution from a stable natural convection to chaotic motion with nonlinear characteristics.

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Numerical Study of Inertial Focusing Behavior of Ellipsoidal Particles in a Microchannel WANG Jianyi, PAN Zhenhai, WU Huiying 2020, 37(6): 677-686.  DOI: 10.19596/j.cnki.1001-246x.8163 Abstract ( )   HTML ( )   PDF (8909KB) ( )   With immersed boundary-lattice Boltzmann method, inertial migration behavior and rotational dynamics of an ellipsoidal particle in an infinite square cross-section microchannel were numerically studied. Two main motion states were found for ellipsoidal particles migrating in a microchannel, i.e., tumbling and log-rolling. It shows that for particles in flow with relatively low Re (Re=10), rotational behavior varied from different initial orientation. However, for particles in flow with higher Re (50≤Re≤200), they perform same rotational behavior and reach the same equilibrium position. As Re number increases, equilibrium position of the ellipsoidal particle moves firstly towards the wall then the center of the channel. At higher Re numbers (Re>300), the particles do not retain stable inertial focusing. Finally, the phenomena were analyzed from flow field around the particles. In addition, mechanism of transition of motion states of particles is explained from fluid and particle inertia.

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Modeling and Simulation of Dynamic Traffic Assignment Based on Conserved Higher-order Model LI Haoyu, LIN Zhiyang, ZHANG Peng, DUAN Yali 2020, 37(6): 687-699.  DOI: 10.19596/j.cnki.1001-246x.8143 Abstract ( )   HTML ( )   PDF (3978KB) ( )   For dynamic traffic assignment problem in road network,we adopt a conserved higher-order (CHO) model for modeling and numerical study. The CHO model is combined with dynamic network loading (DNL) model,and the dynamic network loading model is analyzed through variational inequalities. In numerical simulation,the first-order finite volume method was used to solve the CHO model,and a gradient descent method was used to solve the variational inequality problem of the dynamic network loading model iteratively. Finally,a distribution equilibrium was achieved under the dynamic user optimal condition. The numerical results show that the combination of CHO model and DNL model is feasible for solving the dynamic traffic assignment problem.

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Axial Acoustic Radiation Force of Cylindrical Diverging Waves on a Multilayered Sphere ZANG Yuchen, GAO Jinbiao 2020, 37(6): 700-708.  DOI: 10.19596/j.cnki.1001-246x.8157 Abstract ( )   HTML ( )   PDF (4076KB) ( )   Acoustic radiation force of an incident cylindrical diverging wave exerted on a multilayered sphere is theoretically and numerically studied. Based on sound scattering theory, a closed-form of the acoustic radiation force is obtained and several numerical simulations are provided. It shows unexpectedly that the radiation force becomes negative at selected values of ka and kr0 in a cylindrical diverging progressive wave (where k is the wave number, a is the sphere's radius and r0 is the distance of the sphere from the acoustic source). As kr0 increases to infinity, it degenerates to the case of a plane wave field. Relative thickness of layer affects both magnitude and position of the resonant peaks for a two-layered sphere while it does not significantly affect those for a three-layered sphere. As the innermost layer is substituted by the air, the resonant peaks become more pronounced due to the large difference of acoustic impedance. This study is expected to provide a theoretical basis to develop a new generation of acoustic tweezers using a single beam of progressive waves, which has potential applications in biomedical ultrasound and material sciences.

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Group Velocity and Phase Velocity Analysis of TTI Coal Seam LI Qin, ZHAO Bin, MA Suibo 2020, 37(6): 709-717.  DOI: 10.19596/j.cnki.1001-246x.8151 Abstract ( )   HTML ( )   PDF (20204KB) ( )   We combine group velocity formula and phase velocity formula in tilted transverse isotropy (TTI) media with elastic matrix theory in anisotropic media,and design a model in transversely isotropic (TTI) strata with inclined symmetry axis. According to the model,velocity of TTI coal bed phase velocity changes gently with the change of anisotropic parameter while group velocity change fiercely. Therefore, group velocity determines the wave field shape of anisotropic media; Within a certain range, group and phase velocity for qP wave are greater with increasing ε; Group and phase velocity for qSV wave are greater with increasing δ; Group and phase velocity for qSH wave are greater with increasing γ.

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An Active Thermal Cloak Suitable for Symmetrical Cross Sections LIU Yang, DUAN Yang, XU Guoliang, HUANG Xiaoming, CHEN Xintao 2020, 37(6): 718-724.  DOI: 10.19596/j.cnki.1001-246x.8152 Abstract ( )   HTML ( )   PDF (5655KB) ( )   A method of directly solving the heat conduction equation is used to numerically study a controllable thermal cloaking technology with adaptive heat source.We explore heat flow control method and cloaking effect,and deduce general solution of distribution of adaptive heat source in the thermal cloak region with two-dimensional arbitrary symmetrical section under uniform background. Simulation results show that for a cloak with arbitrary symmetrical section,the adaptive heat source makes disturbed temperature field turn to the background temperature field and achieves the purpose of thermal cloaking.

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Improvement of Evolutionary Ability of Heat Exchange Network Structure with Periodic Advantage Structure Extraction and Search Path Enhancement JIN Yan, CUI Guomin, CAO Mei, SHEN Hao, CHEN Zihe 2020, 37(6): 725-733.  DOI: 10.19596/j.cnki.1001-246x.8147 Abstract ( )   HTML ( )   PDF (1144KB) ( )   To solve the problem that the forced evolutionary random walk algorithm (RWCE) falls into local optimization and reduces search ability in the later stage of optimization,a strategy of combining periodic dominance structure extraction with search path enhancement is proposed. Firstly,population of the system is preliminarily optimized,and the dominant individuals are extracted in certain period.Then these dominant individuals are replicated by multiple paths to other individuals. Finally,according to the search mechanism,they are spread all over the whole solution domain. It shows that the multi-path search strategy centered on dominant individuals improves accuracy of local optimization,increases diversity of population,enhances global search ability,and improves efficiency and quality of optimization.

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Heat Exchanger Network Optimization Using Structural Perturbation Strategy XU Yue, CUI Guomin 2020, 37(6): 734-744.  DOI: 10.19596/j.cnki.1001-246x.8160 Abstract ( )   HTML ( )   PDF (1701KB) ( )   As nodes-based nonstructural model with stream splits (NNM-SS) applied in heat exchanger network synthesis, optimization may be trapped in local optima due to the difficult in generating suitable structures with stream splits. Structural perturbation strategy is proposed and is added into random walk algorithm with compulsive evolution (RWCE-SS). During optimization, a heat exchanger without stream splits is chosen under a certain probability, and then generating a new substream structure on its position to add the number of stream splits in the network. Optimization results obtained by retrofitted algorithm are better than those in literatures.

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Tighter Monogamy Inequality for Squared Tsallis-q Entanglement YUAN Guangming, WANG Xuewen, DONG Minghui, BAI Zhiming, LIU Enchao 2020, 37(6): 745-749.  DOI: 10.19596/j.cnki.1001-246x.8150 Abstract ( )   HTML ( )   PDF (869KB) ( )   Tsallis-q entanglement is a well-known entanglement measures which obeys a tighter monogamy inequality with q∈[2,3]. We extend the range of q for analytic formula of Tsallis-q entanglement to q∈[(5-√13)/2,(5+√13)/2], and prove that it is a tighter monogamy inequality of quantum entanglement in terms of squared Tsallis-q entanglement. It is tighter than existing ones,and the range of q become broader than tighter monogamy inequality using Tsallis-q entanglement.

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Firing Activity of Memristive Neural Network Under Field Coupling ZHOU Qian, WEI Duqu 2020, 37(6): 750-756.  DOI: 10.19596/j.cnki.1001-246x.8168 Abstract ( )   HTML ( )   PDF (8338KB) ( )   In reality, in addition to synapse coupling, magnetic flux coupling between neurons exists. Therefore, it is of practical significance to investigate the firing activity of neural network under field coupling. A Hodgkin-Huxley memristive neural model under field coupling is constructed, in which a distance-weighte between neurons is introduced. Then, effect of time-varying electromagnetic field is described with magnetic flux and a flux-controlled memristor is used to realize coupling between membrane potential and magnetic flux. The influence of distance-weighted and system size on the firing activity of memristive neural model under field coupling is studied. Experimental results show that with the increase of weight, the firing activity of neural network is enhanced. Besides, in order to induce neuronal excitability, threshold of weight increases as system becomes larger. Nevertheless, the evolution behavior of neural network activity with different weight is not affected by the system size. On the other hand, with different weight the evolution behavior of neural network activity of different systems is obviously different. These phenomena demonstrate that the weight and system size are important for the firing activity of memristive neural network under field coupling, and especially, the distance-weighte plays a leading role.