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25 May 2016, Volume 33 Issue 3 Previous Issue    Next Issue

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Level Set Parallel Highly Accurate Evolution Based on GPU Cluster YUAN Bin 2016, 33(3): 253-265.  Abstract ( )   HTML ( )   PDF (3563KB) ( )   We design and implement parallel level set evolution algorithm based on tensor product B-spline which improves accuracy and parallelism of level set evolution. Each step of evolution need compute B-spline coefficients. Furthermore, a parallel high approximation solver for diagonally dominant tridiagonal linear system based on exact LU decomposition is implemented, which is used to compute B-spline coefficients. Two step communications are used to remove communicating dependency, so as to communicate in parallel. As a result, it speeds up level set evolution efficiently.

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Moving Mesh Method for Pitching Naca0012 Airfoil ZENG Xianyang, NI Guoxi 2016, 33(3): 266-272.  Abstract ( )   HTML ( )   PDF (1908KB) ( )   We give discretization for fluid system in integral form with arbitrary moving velocity on unstructured meshes, where re-mapping step in ALE method to interpolate flow variables between old mesh and new one can be avoided. We give three kinds of velocity for different part of computational domain, and apply the scheme to pitching Naca0012 airfoil with moving boundary. It shows that the scheme is efficient and accurate.

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Preconditioning HLLEW Scheme for Flows at All Mach Numbers LIU Zhongyu, ZHANG Mingfeng, ZHENG Guannan, YANG Guowei 2016, 33(3): 273-282.  Abstract ( )   HTML ( )   PDF (2497KB) ( )   Based on HLLEW (Harten-Lax-Van Leer-Einfeldt-Wada) scheme, low speed preconditioning technology is introduced to develop a three-dimensional Navier-Stokes solver for flows at all Mach numbers. Low speed preconditioning techniques is introduced to reconstruct dissipative term in HLLEW scheme and preconditioning HLLEW scheme is proposed. Implicit time-marching method is constructed based on preconditioning Jacobian Matrix. Results of NACA 4412 incompressible flow and RAE 2822 transonic flow with preconditioning HLLEW scheme are compared with results by original method and experimental data. It shows that preconditioning HLLEW method improves accuracy and convergence rate for low speed flow. It can be applied for flows at all Mach numbers.

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Multi-Objective Optimization for Natural Laminar Flow Airfoil in Transonic Flow CHEN Yongbin, TANG Zhili, SHENG Jianda 2016, 33(3): 283-296.  Abstract ( )   HTML ( )   PDF (6789KB) ( )   Multi-objective genetic algorithms are implemented to optimize airfoil shape for obtaining greater laminar range and weaker shock wave drag simultaneously by using a shock control bump. Non dominated solutions of this two-objective optimization problem indicate that aerodynamic performances of airfoils trade-off between delay of profile's transition location and increased intensity of shock wave due the bump installed at upper surface of airfoil.

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Static Instability of Mars Entry Vehicles Flying at Small Angle of Attack LV Junming, MIAO Wenbo, HUANG Fei, CHENG Xiaoli, WANG Qiang 2016, 33(3): 297-304.  Abstract ( )   HTML ( )   PDF (2809KB) ( )   Three-dimensional Navier-Stokes equations in high temperature real gas model and perfect gas model are solved for hypersonic entry process. Good agreement is achieved between numerical results, reference values and flight data of Viking, which validates physical-chemical models and numerical methods. Aerodynamic prediction of Mars Pathfinder proves that results of real gas model are close to LAURA. Perfect gas model with effective specific heat ratio is capable of computing lift and drag coefficients. At 2° angle of attack, MPF exhibits static instability along trajectory, which perfect gas model failed to catch on. It is considered that main reasons of static instability are sonic line shifting around shoulder in windward, subsonic area varying and subsonic bubble occurring in leeward. They result in different pressure change in shock layer and in transportation process from expansion zone to upstream.

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A Field-Equation Turbulence Model Closed By Lagrange Method WANG Lu, XU Jiangrong, LIU Baoyin 2016, 33(3): 305-310.  Abstract ( )   HTML ( )   PDF (2114KB) ( )   First-order moment equations of hybrid second-order moment model are obtained by Euler method, while second-order moment equations are deduced by Lagrange equations. Equations for particle fraction and momentum are provided firstly. A Lagrange model with mean Langevin equations is obtained and Reynold stress equation is deduced, so that hybrid second-order moment model is closed without additional approximate assumptions. Wall-jet-flow loaded with solid particles is simulated. It shows that the model is effective.

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Lattice Boltzmann Simulation of Capture on a Vibrating Cylinder ZHANG Haolong, TAO Shi, GUO Zhaoli 2016, 33(3): 311-321.  Abstract ( )   HTML ( )   PDF (7303KB) ( )   Capture on a vibrating cylinder is simulated. Flow field is obtained with lattice Boltzmann method combined multi-block lattice Boltzmann method. Motion of single particle is calculated with Langevin equation by Lagrange integration. Drag force and Brownian diffusion is considered only. Cylinder does harmonic motion in flow direction with various frequency and amplitude at Re=200. As a result, different flow pattern present. We found capture efficiency raises. Especially at AⅢ vortex pattern, distribution of initial position deviates from center.

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Pressure Dynamic Analysis of Vertical Well Flow with Partial Penetration Fractures LIU Hailong 2016, 33(3): 322-332.  Abstract ( )   HTML ( )   PDF (2899KB) ( )   An actual physical model which shows partial penetration of heterogeneous reservoir formations was built and a three-dimensional mathematical model for instability of anisotropic rectangular reservoirs was built. The mathematical model takes impermeable top, combination of boundary conditions of constant pressure and top border and bottom border into consideration. By using dimensionless transformation, Laplace transformation, Fourier cosine transformation and variable separation methods analytical solution of Laplace domain was obtained. By using Stephenson numerical methods numerical solution pressure of real domain was obtained.Dynamic pressures were plotted and sensitivity analysis was carried out.Pressures obtained are basically consistent with numerical simulation, which shows reliability of the method. Sensitivity analysis shows that:Dynamic pressure curve can be divided into early linear flow, mid-radial flow, late spherical flow and boundary control flow.Fracture length mainly affects early linear flow. Permeability anisotropy mainly affects mid-radial flow.Degree of penetration in reservoir and fracture orientation mainly affect late spherical flow.Boundary conditions and reservoir border width mainly affect boundary control flow.Optimal degree of open shot, vertical permeability and other parameters can be obtained easily.It provides theoretical guidance for reservoir engineering analysis and fracturing process design.

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E-H Time-Domain Finite-Element Method with Hierarchical Vector Basis Functions for Analysis of Cavity and Waveguide Structures YE Zhenbao, ZHOU Haijing 2016, 33(3): 333-340.  Abstract ( )   HTML ( )   PDF (1622KB) ( )   We present E-H time-domain finite-element method using hierarchical high-order vector basis functions. Electric fields and magnetic fields are computed together and Crank-Nicolson difference scheme is implemented to obtain an unconditionally stable algorithm. Meanwhile, perfectly matched layers are used for truncation of unbounded regions. Three-dimensional cavity and waveguide structures are simulated. It shows that accuracy is improved by E-H TDFEM method with higher-order basis functions.

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Barycentric Lagrange Interpolation Collocation Method for Two-dimensional Hyperbolic Telegraph Equation LIU Ting, MA Wentao 2016, 33(3): 341-348.  Abstract ( )   HTML ( )   PDF (590KB) ( )   We propose a numerical scheme for two-dimensional hyperbolic telegraph equation, in which Chebyshev-Gauss-Lobatto collocation nodes and approximate solutions with multi-variable barycentric Lagrange interpolation functions are used. Multi-variable barycentric Lagrange interpolation functions are given for spatial, temporal variable and their derivatives. Accuracy of the method is demonstrated with test examples with Dirichlet and Neumann boundary conditions. Numerical results are more accurate than numerical solutions in literatures. In additional, the method is easy to implement for multidimensional problems.

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Optimization of Heat Integration in Dynamic Multi-agent Differential Evolution Algorithm CHEN Shang, CUI Guomin, ZHANG Chunwei, DUAN Huanhuan 2016, 33(3): 349-357.  Abstract ( )   HTML ( )   PDF (1864KB) ( )   For optimization problem of heat integration system, serious nonlinear and non-convex heat exchanger network belonging to multi-extremum and multi-dimensional problems are considered. Dynamic multi-agent differential evolution algorithm is provided to solve the problem. It makes use of sensing capability of multi-agent with dynamic update strategy, which improves formation mechanism of population and mutation mechanism of differential evolution algorithm and globle searching ability in large scale nonlinear system. The algorithm was applied to 10SP2 and 9SP1 cases of heat exchanger network problems. Better total annual cost is obtained, which indicates better globle searching ability of the algorithm.

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A Generalized Finite Element for Plane-Strain Problem YANG Pu, NIU Hongpan, XIAO Shifu 2016, 33(3): 358-366.  Abstract ( )   HTML ( )   PDF (2505KB) ( )   Considering advantages of generalized finite element and rational finite element a kind of quadrilateral elements (generalized element) is developed for plane-strain problem. The element includes Poisson's effect. Additional terms of displacement mode inside element are constructed according to semianalytical solution of node displacement degrees of freedom constraint elastic plane strain equation. The element reflects real displacement field accurately and elemental calculation accuracy was improved. Shape functions of generalized elements and generalized isoparametric elements are constructed and patch test and numerical tests are designed to verify calculation accuracy. Numerical tests indicate that whether in regular or irregular grid new element has higher accuracy than conventional element and generalized element. The element is convenient for implementation, which is suitable for practical engineering.

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Phase Field Modeling of Columnar Grain Growth:Effect of Second-Phase Particles LUO Zhirong, GAO Yingjun, MAO Hong, LU Chengjian, HUANG Shiye 2016, 33(3): 367-373.  Abstract ( )   HTML ( )   PDF (2450KB) ( )   In a moving hot zone model with uniform temperature and an infinite temperature gradient under directional annealing, effect of second-phase particles (SPPs) on growth of columnar grain microstructure in polycrystalline materials was studied with phase field method. It shows that SPPs inhibit formation of columnar grain structure and inhibitory effect increases with increasing volume fraction of SPPs and decreasing size of SPPs. Effect of SPPs on final grain radius follows Zener relation under condition of directional annealing. Volume fraction of SPPs and their dispersive distribution at grain boundaries in materials should be reduced as far as possible to obtain better columnar grain structures during directional annealing.

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First Principles Study on Adsorbing of Fe on N Doping Carbon Nanotube Rings YANG Zhonghua, LIU Guili, QU Yingdong, LI Rongde 2016, 33(3): 374-378.  Abstract ( )   HTML ( )   PDF (1878KB) ( )   CASTEP program based on density functional theory was employed to study adsorbing of Fe on N doping carbon nanotube rings under deformation. It shows that bonding energy of new construction is negative, which satisfying energy conditions of stable existence. Adsorbing energies of Fe are enhanced since activities of doping system are increased to form Fe-N covalent bonds easily. Increasing stretch and compression deformations linearly, adsorbing energies of Fe reduce rapidly in parabola shape. They are more sensitive to stretch deformations.