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25 July 2008, Volume 25 Issue 4 Previous Issue    Next Issue

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High Order FD-WENO Schemes for Rayleigh-Taylor Instability Problems LI Shoufu, YE Wenhua, ZHANG Yuan, SHU Shi, XIAO Aiguo 2008, 25(4): 379-386.  Abstract ( )   PDF (611KB) ( )   High order weighted essentially non-oscillatory finite difference schemes (FD-WENO) are applied successfully to numerical simulation of gravity-driven high density ratio Rayleigh-Taylor instability problems and laser ablative Rayleigh-Taylor instability problems in two dimensions. It provides important references to numerical study of inertial confinement fusion (ICF) as well as to other high-tech fields. High order FD-WENO schemes are applicable to numerical simulation of ICF inplosion.

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High Order Hybrid Centrai-WENO AMR Method for Gaseous Detonation LIU Guozhao, ZHANG Shudao 2008, 25(4): 387-395.  Abstract ( )   PDF (540KB) ( )   A high order hybrid central-WENO finite difference scheme with adaptive mesh refinement (AMR) for numerical simulation of gaseous detonations is presented. Governing equations are two-and three-dimensional reactive Euler equations in a ZND detonation model. The hybrid scheme combines high order central finite difference schemes and WENO schemes effectively. In high gradient regions, WENO schemes are empolyed to capture discontinuity, while in smooth regions a more efficient and accurate central finite difference scheme is adopted. The AMR grid is based on flow field structure. Numerical results show that a hybrid scheme with AMR method has characteristics of high-order, high-resolution, and high-efficiency.

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Simulation of Complex Flows with Large-scale Moving Boundaries WANG Bing, XU Houqian 2008, 25(4): 396-400.  Abstract ( )   PDF (306KB) ( )   Complex flow with large-scale moving boundaries is divided into a moving boundary zone and a common flow zone connected by a special interior boundary named zone interface. Local remeshing method is applied to deal with grid-reforming of a high-speed bullet. The axis is defined as a special grid-deforming boundary to avoid negative volume of grid near the axis. Arbitrary Lagrangian-Eulerian (ALE) formulation is used to solve unsteady process of a bullet leaving a muzzle. It indicates that the bullet is accelerated and then decelerated gradually.

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Asymmetric Jet Formation in Finite-distance Flow Metallic Collisions SHI Yina, QIN Chengsen, FENG Qijing, HANG Yihong 2008, 25(4): 401-406.  Abstract ( )   PDF (386KB) ( )   We study asymmetric jet and slug formation in collision of two plane flows at a finite distance from stagnation point. Analytic expressions for width and flow direction of jet and slug are given on a solution ellipse. The jetting process is simulated with Euler hydrocode of high order precision and YOUNGS algorithm for tracking interfaces. Predictions are more accurate than results of other analytic models and are in agreement with KS experimental data. With increase of asymmetry between incoming flows, flow direction of slug changes considerably, whereas the direction of jet barely deviates from the direction of symmetric bisector of incoming flows.

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Refraction of Shock Waves at Fe-Be Interface YU Ming, CHENG Junbo 2008, 25(4): 407-413.  Abstract ( )   PDF (453KB) ( )   We investigate numerically refraction of shock waves at ferrum-beryllium (Fe-Be) interface. Equations of state for Fe and Be adopt "stiffen gas" formulas. A shock polar theory is employed to analyze critical angles of transition from regular refraction to irregular refraction. A shock-capturing method in finite volume scheme with two order of precision and wave propagation is employed to discretize and solve hydrodynamics equations of shock waves. For regular refraction, numerical results agree well with shock polar theory. For irregular refraction, precursory refracted shock waves are observed, and refraction images vary with shock intensity and incident angles.

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Effect of Penetration in HPCOIL LV Junming, HU Zongmin, JIANG Zonglin 2008, 25(4): 414-420.  Abstract ( )   PDF (438KB) ( )   Three-dimensional CFD technology is applied in an RADICL model by solving laminar Navier-Stokes equations and transportation equations. Mixing and reaction of flows, gas-dynamics fields and gains are studied at different jet intensity. It is found that the penetration depth plays an important role for special distribution of small signal gain macroscopically. Strong impinges between jets and unsteady structures are induced by over-penetration in mixing flow field.

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Simulation of 3D Hypersonic Ionized and Radiating Flows in Thermal and Chemical Nonequilibrium WANG Yibin, WU Yizhao, LIU Xueqiang 2008, 25(4): 421-426.  Abstract ( )   PDF (439KB) ( )   A numerical method applicable to unstructured mesh is proposed to compute 3D hypersonic ionized and radiating flowfields in thermo-chemical nonequilibrium. The flowfield is described with multi-specy N-S equations. The chemical model includes 11 species(O2, N2, O,N, NO, NO+, N+, O+, N2+, O2+, e-) and 20 reactions. For thermal nonequilibrium effect, a two temperature model is considered. Radiation transfer equation (RTE) is solved with finite volume method. Numerical result on MUSES-C is shown and compared with referenced data. Influence of radiation on flowfield is discussed.

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Recursive Box Method for Wall Distance Computation ZHAO Huiyong, HE Xuzhao, LE Jialing 2008, 25(4): 427-430.  Abstract ( )   PDF (304KB) ( )   A recursive-box method is proposed to compute wall distance in a turbulence model. The method is efficient, general and robust. For 3D and 2D problems, compared with a direct method, the recursive-box method obtains similar results and reduces computational time by one order of magnitude. Moreover, the denser the grids are, the higher efficiency of recursive-box is.

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Keeping Volume Fraction of Fluid in Reconstructing Moving-interfaces of VOF on Rectangular Meshes WANG Ruyun, CHEN Pingping, BAN Changying 2008, 25(4): 431-436.  Abstract ( )   PDF (453KB) ( )   A moving interface reconstructing algorithm keeping volumed fraction of fluid in the volume of fluids (VOF) method is presented. The moving interface is approximated by a diagonal line of a grid, and two diagonal lines located in adjacent grids intersect on a public side. By keeping constant volume fraction of fluid in each grid, nonlinear equations are built on boundary grids, location of intersecting points of moving-interfaces with grid sides are decided by solving equations. The shape of moving-interfaces is reconstructed. The method simulates accurately moving interfaces with fewer cusps. Its availability and efficiency are demonstrated.

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Difference Schemes on Vertical Grids in a Hydrostatic Model LIU Yudi, CHENG Huhua, HOU Zhiming 2008, 25(4): 437-444.  Abstract ( )   PDF (347KB) ( )   To study forth-order compact schemes in numerical atmospheric or oceanic models, a general method is proposed for dispersion relation of hydrostatic linear baroclinic adjustment equations with differential or difference schemes, at horizontal length of 100 km, 10 km and I kin, respectively. Non-staggered grids (N grids), Lorenz grids (L grids), Charney-Phillips grids (CP grids), Lorenz time staggered grids (LTS grids) and Charney-Phillips time staggered grids (CPTS grids) in a second-order centered scheme and a forth-order compact scheme are compared. The forth-order compact scheme reduces errors of frequency, horizontal and vertical component of group velocity on N grids, CP grids and CPTS grids obviously, but increases errors of horizontal and vertical component of group velocity on LTS grids.

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Natural Convection in a Wavy Enclosure Filled with Porous Media ZENG Min, WANG Gang, XIE Gongnan, CHEN Qiuyang, WANG Qiuwang 2008, 25(4): 445-449.  Abstract ( )   PDF (398KB) ( )   We study heat transfer and fluid flow in a complex enclosure fiLled with porous media, with SIMPLEC (Semi-Implicit Method for Pressure Linked Equations Consistent) algorithm in curvilinear coordinates. The upper and lower walls of the enclosure are horizontal and adiabatic. The vertical wall forms cosine curve and is kept at a constant temperature. Governing equations are discretized with a finite-volume method on body-fitted coLlocated grids. Brinkman-extended-Darey model and local thermal non-equilibrium model are used to solve momentum and energy equations. Effects of parameters, such as Rayleigh numbers, Darey numbers and porosity, on heat transfer and fluid flow are studied. It is shown that Rayleigh numbers and Darey numbers have significant effect while porosity is negligible. There exists an optimal aspect ratio to make the heat transfer rate maximum.

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Numerical Analysis on Thermal Radiation-electricity Module in a Thermophotovoltaic System MAO Lei, YE Hong, CHENG Qian 2008, 25(4): 450-456.  Abstract ( )   PDF (426KB) ( )   Physical and numerical model for a thermal radiation-electricity module in a TPV (Thermophotovoltatic) system is constructed. Current/voltage characters of the system consisting of a SiC emitter and GaSb or Si PV cells are obtained. Influences of emitter and cell temperatures are analyzed for a SiC emitter with GaSb cells. As emitter temperature rises from 1 400 K to 1 900 K, system electric power density increases from 0.67 W· cm-2 to 5.43 W· cm-2, and cell efficiency increases from 16.3% to 24.8%. However, the rise of cell temperature causes an opposite trend. As cell temperature rises 10K, system electric power density deceases about 0.15 W· cm-2, and the cell efficiency deceases dramatically. The radiative energy distribution of a selective emitter with GaSb cells is discussed. Unusable radiative energy of the selective emitter can be reduced remarkably compared to a SiC emitter and thus improves system performance and stability effciently.

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Molecular Dynamics Study on Thermal Conductivity of Porous Argon Thin Films LIU Qixin, JIANG Peixue, XIANG Heng 2008, 25(4): 457-462.  Abstract ( )   PDF (314KB) ( )   In a classical Lennard-Jones potential model, we present molecular dynamics study on thermal conductivity of porous argon thin films. It shows that thermal conductivity of porous argon thin films is remarkably lower than that of pure argon thin films. Larger porosity results in lower thermal conductivity, A thermal conductivity model based on parallel method is used to analyze thermal conductivity of argon porous thin films. It shows that pore configuration in film affects thermal conductivity.

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Tikhonov Regularization Determination of Interfacial Heat Transfer Coefficient in Metal Solidification SUI Dashan, CUI Zhenshan 2008, 25(4): 463-469.  Abstract ( )   PDF (356KB) ( )   Interfacial heat transfer coefficient (IHTC) between casting and mould is an essential boundary condition in simulation of metal solidification. We present an inverse method based on Tikhonov regularization theory. A regularized functional is established and regularization parameters are deduced with Arcangeli criterion and Morozov discrepancy principle. The functional is solved by sensitivity coefficients and Newton-Raphson iteration method. The regularization method ensures stability and accuracy of determination and overcomes ill-pesedness of inverse heat conduction problems (IHCP). It shows better accuracy especially with increasing error of measurement temperature.

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Classical Dynamics of a Hydrogen Molecular Ion (H2+) Intense Laser Fields:1D and 3D Models GUO Jing, LIU Shixing, XU Tianfu, LIU Xueshen, DING Peizhu 2008, 25(4): 470-476.  Abstract ( )   PDF (364KB) ( )   Classical trajectory method is used in 1D and 3D models to study classical dynamics of Hydrogen molecular ion (H2+) in intense laser fields. Probabilities of survival, ionization, dissociation and Coulomb explosion and average distance between electron and the mass-center are calculated. It is shown that the 1D model is available for dynamics of hydrogen molecular ion in intense laser fields.

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Monte Carlo Method for Nonlinear Neutron Transport LI Shu, TIAN Dongfeng, DENG Li 2008, 25(4): 477-482.  Abstract ( )   PDF (292KB) ( )   An approximate linearization method is proposed for nonlinear neutron transport equations. The equation is deduced to a form suitable for Monte Carlo simulations. Numerical results show that it is reasonable. It provides a tool for simulating high energy neutron transportation.

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Study on a Three-dimensional Photonic Crystal Pressure Sensor WEI Yiming 2008, 25(4): 483-487.  Abstract ( )   PDF (422KB) ( )   Band structure and characteristics of polystyrene three-dimensional photonic crystals are analysed with a plane-wave method. Effects of pressure on polystyrene three-dimensional photonic crystals are studied. Linear relation between pressure ranging from 0 to 41.3 MPa and normalised frequency ranging from 0.596 to 0.608 nm is shown. Since structure scale of photonic crystal is close to the wave-length, it is possible to realize three-dimensional photonic crystal pressure sensors with high accuracy.

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Molecular Simulation on Migration of Kinks on a 30° Partial Dislocation in Silicon WANG Chaoying, MENG Qingyuan, LI Chengxiang, ZHONG Kangyou, YANG Zhifu 2008, 25(4): 488-492.  Abstract ( )   PDF (375KB) ( )   Left kink (LK) and right kink (RK) migration and velocity at different temperatures and shear stresses are obtained with molecular dynamics (MD) method. By means of nudged elastic band method (NEB) based on tight binding (TB) potential, migration energies of LK and RK are calculated. It shows that due to high migration energy a single LK or RK moves slowly. Multiple kink pair structure of LK and RK-reconstruction defect (RC) dissociated from RK accelerate motion of LK and RK. Particularly, RC makes 30° partial dislocation move faster.

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Sound Fields in a Concave Spherical Transducer with Linear Superposition of Rayleigh Integrals CHENG Jianzheng, ZHOU Yulu, MAO Yanxin, ZHANG Dejun 2008, 25(4): 493-498.  Abstract ( )   PDF (394KB) ( )   A method called Rayleigh integral linear superposition algorithm is introduced, in which nonlinear propagation and high order harmonic attenuation are considered. Principle of the method is analyzed. For a concave spherical transducer, medium attenuation and nonlinear propagation in sound focused region are studied. The method is compared with Khokhov-Zabolotskaya-Kuznesov (KZK) method. It is shown that the method is effective in calculating high-intensity focused ultrasound(HIFU) sound fields.

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Coarse Graining Method in Lempel-Ziv Complexity Arithmetic ZHANG Dianzhong 2008, 25(4): 499-504.  Abstract ( )   PDF (432KB) ( )   To improve noisepmof ability and stability of Lempel-Ziv complexity (LZC), LZC is calculated by an equiprobable coarse graining method. Relation between threshold of bi-quantified coarse graining and LZC is analyzed. An anti-jamming test is performed with 87 series generated by Logistic map. Correlation coefficients and relative variance coefficients of LZC series before and after noise inject are used to measure noiseproof ability of LZC indexes. 10 electroencephalograms are used to test stability of LZC. It shows that with equiprobable coarse graining, correlation coefficients are more than 0.998, relative variance coefficients are smaller and stability of LZC of electroencephalogram is good.