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25 September 2016, Volume 33 Issue 5 Previous Issue    Next Issue

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A Highly-efficient Discrete Boltzmann Model for Detonation ZHANG Yudong, XU Aiguo, ZHANG Guangcai, ZHU Chengmin 2016, 33(5): 505-515.  Abstract ( )   HTML ( )   PDF (4131KB) ( )   A discrete Boltzmann model is presented for detonation simulation. It consists of a discrete Boltzmann equation and a phenomenological reaction rate equation. In physical modeling, it is equivalent to a traditional Navier-Stokes model and a coarse grained model for thermodynamic non-equilibrium behavior. Compared with traditional fluid model, it provides more dynamic information and more kinetic information as well. The model adopts 16 discrete velocities, which has high computational efficiency. Additional degrees of freedom are introduced so that it can be used to simulate various detonations with different specific heat ratios. Several classic examples of detonation are simulated to validate the model. It shows that besides detonation dynamics where traditional hydrodynamic model works, it can also be used to study non-equilibrium effects where traditional fluid model does not work.

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Numerical Inlet and Outlet Boundary Conditions in SPH Method ZHOU Jie, XU Shengli 2016, 33(5): 516-522.  Abstract ( )   HTML ( )   PDF (2954KB) ( )   With concepts of virtual particles, we present a method for inlet and outlet boundary conditions. Inlet zone is located just outside inlet boundary, which is defined and filled with virtual particles. Outlet and buffer zones are located just outside outlet boundary. Quantities of outlet boundary virtual particles are calculated, and quantities of buffer boundary virtual particles are imposed. According to stream status of every time step, zone property of fluid particles could to be changed. Relevant fluid particles are added or remored, when boundary virtual particles inflow or outflow fluid domain. With SPH method based on N-S equation, two-dimensional pipe flow is used to verify boundary conditions. Finally boundary conditions applied in calculation models of shock tube and flow around a cylinder are studied. Inlet and outlet boundary conditions are proposed to avoid fluid particles integral truncation near border, and to assure fluid particles and shock wave flow out boundary.

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A 2D Cell-centered MMALE Method Based on MOF Interface Reconstruction JIA Zupeng, SUN Yutao 2016, 33(5): 523-538.  Abstract ( )   HTML ( )   PDF (12868KB) ( )   A 2D cell-centered multi-material arbitrary Lagrangian-Eulerian(MMALE) method based on moment of fluid(MOF) interface reconstruction is developed. Hydrodynamic equations are discretized and solved by cell-centered Lagrangian scheme. Tipton's pressure relaxation model is adopted as closure model for mixed cells. MOF method is simplified and improved to reconstruct interface in mixed cells. A conservative integral remapping algorithm based on cell-intersection is used in remapping phase. Several numerical examples are given, such as 2D periodic vortex problem, Sedov problem, interaction of a shock wave with an helium bubble,a strong water shock impacting on a cylindrical air bubble in water,2D Rayleigh-Taylor instability, etc.It shows that the method is of second order accurate, and is capable of computing problems involving large density and/or pressure ratios across interface. Its robustness is better than that of staggered MMALE method and it is applicable to complex multi-material hydrodynamic problems.

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Influence of Wind Sand Flow on Potential and Electric Field Distributions Along High Voltage Insulators TANG Qiuming, GAO Qiang 2016, 33(5): 539-546.  Abstract ( )   HTML ( )   PDF (3165KB) ( )   Wind sand flows affect surface electric field and potential on insulators. We established a gas-solid flow model for insulator surrounded by sand and a sand-electricity coupling model made up of high voltage insulator based on finite volume method (FVM). Spatial distribution and deposition of sand on surface of insulator and electric field distribution along insulator under different wind sand flow are calculated. It shows that surface potential and electric field distortion are influenced obviously by wind speed and particle size. Distortion of electric potential increases with increase of wind speed and particle size, while distortion of electric field decreases with increase of wind speed and particle size. Different spatial distribution and deposition of sand make different distortion on potential and electric field along insulator.

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Optical Tamm States with Three Dispersion Models of Metals Dielectric Constant JIANG Helun, LIU Qineng 2016, 33(5): 547-553.  Abstract ( )   HTML ( )   PDF (2115KB) ( )   To investigate metal dielectric constant influence on optical Tamm state, complex refractive index in three dispersion models is studied. TE wave and TM wave of optical Tamm state with different incident angle and silver layer thickness and cycles number are studied in silver-photonic crystal-silver structure. Two optical Tamm state appeare (OTS1 and OTS2). In three dispersion models wavelength of optical Tamm state changing with incident angle and silver layer thickness and cycles number are similar. Transmission peak of optical Tamm state changing with incident angle and silver layer thickness and cycles number are different. Drude-Lorentz model and Lorentz model can describe characteristics of silver, but the Drude model can't.

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Adsorbing of Magnesium on Phosphorus-Doping Single-Walled Silicon Nanotubes: First-principles Study ZHOU Shuang, LIU Guili, JIANG Yan, SONG Yuanyuan 2016, 33(5): 554-560.  Abstract ( )   HTML ( )   PDF (3132KB) ( )   Adsorption characteristics of magnesium atoms on phosphorus-doped single-walled silicon nanotubes (SWSiNTs) are studied using plane wave pseudopotential method with generalized gradient approximation based on density functional theory. Adsorption energies of magnesium atoms on pure,phosphorus-doped and deformation effects (compressive or tensile) (6,6) SWSiNTs are calculated. Bond and Mulliken population of both pure and phosphorus-doped SWSiNTs are also analyzed.It shows that covalent bond and ionic bond conexist in armchair silicon nanotube superlattices doped with phosphorus atoms by forming ionic bond of Mg-P and Si-P,and enhancing ionic bond of Si-Si. Adsorption energy of Mg atom on SWSiNTs are improved significantly by doping phosphorus atoms. Adsorption energy are also increased under compressive deformation at 0.25%,0.50%,1.00%,1.25% and tensile deformation at 1.00%,1.25%. It enhances adhesion of interface of silicon nanotubes as reinforce combined with matrix.

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A Strategy of Differential Evolution with Opposition-based Multi-population Parallel DUAN Huanhuan, CUI Guomin, CHEN Jiaxing, CHEN Shang 2016, 33(5): 561-569.  Abstract ( )   HTML ( )   PDF (1502KB) ( )   Generally, differential evolution (DE) algorithm is easily stuck into local optima as well as suffers from low convergence accuracy when employed for optimization of heat exchanger network. To solve these issues, an opposition-based multi-population parallel differential evolution algorithm is proposed. Firstly, opposite population is built by using initial population. Then, new generation of individuals are generated through information exchange, which is produced by mutated operation between opposite population and its original correspondence. The final step is to retain evolution of multi-population in parallel by applying multi-round opposites, so that the population is enable to keep current solution information and search new solutions in a larger space as well. Computing results of improved DE algorithm on 9sp and 15sp suggests that the method improves population diversity, jumps out local optima and at the same time achieves higher speed and accuracy.

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Simulation of VENUS-III Benchmark Experiment by JMCT Monte Carlo Code LIU Xiongguo, DENG Li, HU Zehua, LI Rui, Fu Yuanguang, LI Gang 2016, 33(5): 570-580.  Abstract ( )   HTML ( )   PDF (2751KB) ( )   VENUS-III benchmark was simulated based on 3-D general-purpose Monte Carlo coupled neutron and photon transport code JMCT (J Monte Carlo Transport Code). It includes detailed modeling, criticality calculation and shielding calculation. Firstly, criticality calculation is done, in which keff eigenvalue, fluxes in importance regions and energy spectrums are calculated. Almost same results are achieved by JMCT and MCNP. Warp of keff is about 0.24% the flux warp is less than 1%. Then, deep penetration shielding is simulated, in which fixed source is used. Tally includes fluxes of detectors in different locations. Calculated results agree well with experimental data. The most warps of JMCT and tests are within target accuracy of ±15%. It satisfies requirement of shielding calculation. It shows that JMCT code suits well for criticality and shielding simulation.

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Design and Realization of Mesh Tally in General Monte Carlo Particle Transport Code JMCT FU Yuanguang, ZHENG Jianhua, SHANGGUAN Danhua, LI Rui, LI Gang, MA Yan, DENG Li 2016, 33(5): 581-586.  Abstract ( )   HTML ( )   PDF (4704KB) ( )   Mesh tally function of monte Carlo method can give a detailed and intensive calculation of flux distribution in specific volumes. To realize such function in JMCT mesh tally function are designed and realized. It supports non-uniform mesh in three kinds of orthogonal geometry (xyz of rectangular coordinates, rθz of cylindrical coordinates, and rθφ of spherical coordinates). Algorithm for rectangular coordinates is discussed. Calculation on DAYAWAN reactor core pin-by-pin model, Venus benchmark model and a 1-D ITER model verifies preliminarily correctness of JMCT mesh tally. Furthermore, U-array benchmark model is used to test serial performance of JMCT mesh tally. Both JMCT and MCNP5 use same xyz mesh grids and run under same condition. It shows that JMCT takes less time consuming and has higher performance dealing with xyz geometry.

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Realization of Optimal Grid Searching in JMCT LI Rui, LI Gang, ZHANG Baoyin, DENG Li, WANG Wei 2016, 33(5): 587-592.  Abstract ( )   HTML ( )   PDF (1037KB) ( )   Time consuming analysis of grid search in JMCT, a continuous-energy Monte Carlo neutron transport code, is done. Region projecting acceleration is performed on grids of main energy, fission yield neutron and unresolved resonance data. Quality of project grid is shown with arithmetic progression and geometric progression. At last, optimized grid search is test on several k∞ problems. The models are fuel lattice cell at begin of cycle and middle of cycle. It shows that optimized grid search improves speed of JMCT remarkably in middle of cycle problem.

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Automatic Source Particle Biasing Sampling Function of JMCT and Its Application QIU Youheng, DENG Li, SHANGGUAN Danhua, ZHENG Zheng 2016, 33(5): 593-598.  Abstract ( )   HTML ( )   PDF (1740KB) ( )   Multigroup neutron adjoint transport and automatic source particle biasing sampling function of JMCT is introduced. A press water reactor shielding neutron flux is achieved by JMCT with source biasing sampling technique, which is well accord with experiment. Its computation efficiency is higher than that of MCNP using geometry important method.

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3D Discrete Ordinates-Monte Carlo Coupling Method for Nuclear Power Plant Cavity Streaming Calculation ZHENG Zheng, WANG Mengqi, LI Hui, MEI Qiliang 2016, 33(5): 599-605.  Abstract ( )   HTML ( )   PDF (6585KB) ( )   By combining advantages of SN method (high calculational efficiency) and advantages of MC method (fine geometrical modelling), three-dimensional discrete ordinates-Monte Carlo method (3D SN-MC coupling method) is able to calculate cavity streaming dose rate in short time. SN-MC coupling method is applied on Qinshan No.1 reactor and CAP1400 reactor cavity streaming calculation. Results of SN-MC coupling method are compared with measurements and results of MCNP bootstrapping method. It shows that theoretical model and codes of 3D SN-MC coupling method are both correct.

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Design and Development of Auto-Modeling Tool JLAMT for Field Application of Large-scale Models MA Yan, FU Yuanguang, QIN Guiming, DENG Li, LI Gang, SHANGGUAN Danhua, HU Zehua, HU Xiaoli, LI Rui, CHENG Tangpei 2016, 33(5): 606-612.  Abstract ( )   HTML ( )   PDF (5342KB) ( )   In order to develop large-scale transport simulation (such as simulation of whole reactor core pin-by-pin problem), we developed a neutron photon coupled transport code JMCT. In this article, developing idea of a auto modeling tool JLAMT based on field oriented development is introduced. JLAMT developed several quick and assembly modeling tools. Data structure based on hierarchical geometry tree was designed. Automatic conversion and generation of physical model input file for GDML file format are made. By using those modeling tools, complex devices (include DAYAWAN whole-core model) were created, and transformed file was delivered to JMCT for transport calculation. Results were validated for correctness of visual modeling tools.

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Dose Coefficient Calculation of External Exposure of Radionuclides Based on Chinese Reference Voxel Phantom LU Wei, WU Zhen, QIU Rui, LI Chunyan, YANG Bo, LI Junli 2016, 33(5): 613-624.  Abstract ( )   HTML ( )   PDF (2160KB) ( )   Dose coefficients for external photon radiation are widely used for assessment of radiation dose to public and workers due to ground surface contamination and air immersion of radionuclides released in nuclear accidents. Dose coefficients based on Chinese reference voxel phantom were presented. Photons that incident into the cylinder, which is slightly larger than phantom, is simulated using Geant4, including distributions of angle, height and energy of photons; Secondly, photons are sampled on surface of cylinder around Chinese Reference Male/Female Voxel Phantom with MCNPX 2.4.k from the above source, dose coefficients of 20 initial gamma ray energies, from 15keV to 10 MeV, are calculated. Thirdly, dose coefficients of 68 important nuclides are evaluated by combining of decay data from ICRP 107 and photon coefficients using cubic-spline fitting. GB/T 17982-2000 shows an overestimation for ground contamination while an underestimation of high Z nuclides for air immersion compared to our results.

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Simulation of Moderator for Improving Measurement Accuracy of Elements in PGNAA Coal Online Measurement System SHAN Qing, CAI Pingkun, CHU Shengnan 2016, 33(5): 625-630.  Abstract ( )   HTML ( )   PDF (1592KB) ( )   Two optimizing schemes of moderator are proposed. In the first scheme two channels are directly added to initial moderator, and in the second scheme two channels are introduced after adding a lead layer to initial moderator. Monte Carlo simulations are carried out for two optimizing schemes. It shows that the first scheme can improve measurement accuracy of carbon and oxygen, but it decreases measurement accuracy of other elements such as H and Si. In the second scheme, measurement accuracy of all elements can be increased as selecting proper thickness of lead and inclination of channels.