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Control volume method for the dynamo problem in the sphere with the free rotating inner core

STUDIA GEOPHYSICA ET GEODAETICA 2003年第1期47卷 147-159页

作者： Hejda, P Reshetnyak, M Acad Sci Czech Republ Inst Geophys CR-14131 Prague 4 Czech Republic Russian Acad Sci Inst Phys Earth Moscow 123995 Russia Moscow MV Lomonosov State Univ Ctr Res Comp Moscow 119899 Russia

A model of thermally driven dynamo in the Boussinesq approximation in the spherical shell with the free rotating inner core is considered. To solve equations we use a new in dynamo modeling control volume technique (for details of this method for hydrodynamics see Patankar, 1980). The main advantage of this method over previous attempts to solve magnetohydrodynamics equations in the spherical grids is that no filtering of high harmonics in the pole regions is needed. We present the results of simulations for the self-consistent dynamo system evolution over the diffusion time and longer periods. Different ways of stabilizations of magnetohydrodynamics equations, when convective terms are of the same order (or larger) as conductive ones, are considered.

关键词： hydromagnetic dynamo finite volumes simple algorithm up-wind scheme

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Study on Antigravity Mold Filling by Conservative Scalar Method

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Journal of Shanghai University(English Edition) 2003年第2期7卷 196-200页

作者：李日王友序杨根仓毛协民 SchoolofMaterialsScienceandEngineering DepartmentofMaterialsScienceandTechnology

By simple method and Van Leer scheme, a program on numerical simulation for 3D mold filling has been developed. The fluid flow field of gas and liquid is calculated in couples by a single phase N S equation using simple method, and free surface control equation is handled by Van Leer scheme. Then it is verified by an anti gravity mold filling of thin wall plate. In order to demonstrate its ability to simulate 3D casting, an anti gravity mould filling of a cube is computed by the program.

关键词： thin wall casting numerical simulation 3D mold filling simple algorithm Van Leer scheme.

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A MODIFIED simple algorithm FOR 2-D FLOW IN OPEN CHANNEL

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Journal of Hydrodynamics 2000年第3期12卷 68-74页

作者： Han Long-xi, Jin Zhong-qing College of Water Resources and Environment, Hohai Universit y, Nanjing 210024, P.R.China College of Water Resources and Environment Hohai University Nanjing 210024 P.R.China

For two-dimensional wa ter flow in open channel, by discritizing hydrodynamic differential equation of conservative form, the corresponding algebraic equations were derived which invo lve the relationship between velocity and depth. Based on the relationship, this paper deduced a modified formula of velocity correction for simple algorithm. A s a test case, the flow in a prismatic channel with two different slopes was com puted and a good result was obtained.

关键词： two-dimensional flow conservative form simple algorithm velocity correction

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Cascade arc studies of hydrogen/nitrogen plasmas in nonequilibrium

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JOURNAL OF PROPULSION AND POWER 2002年第1期18卷 176-183页

作者： Moeller, T Keefer, D Rhodes, R Univ Tennessee Inst Space Tullahoma TN 37388 USA

A cascade arc facility was developed to study the characteristics of nonequilibrium plasma propellants for electric propulsion applications. The cascade arc was operated with 50 A hydrogen arcs at absolute pressures of 1.34 x 10(4) and 4.14 x 10(4) Pa. Spatially resolved spectral emission data were collected using a two-dimensional optical multichannel analyzer (OMA), and radial distributions of H-alpha line widths of the Abel inverted emission line profiles were obtained. The measured H-alpha line widths were compared to values predicted by nonequilibrium cascade are simulations using the UTSI Cascade Arc Plasma Simulation (CAPS) code and dynamic ion Stark broadening/electron number density correlations. Agreement was sensitive to the finite-rate kinetic model used for hydrogen. When used in CA-PS, University of Illinois kinetics model gave the best agreement with the hydrogen cascade arc measurements. The experimental electric field and radially resolved H-alpha line widths accurately predicted measured values at both pressures within experimental uncertainty. H-alpha line widths for simulated ammonia and hydrazine were also obtained at pressures of 1.34 x 10(4), 4.14 x 10(4), and 6.89 x 10(4) Pa. These mixture data can be used for future evaluations of kinetic models for hydrogen/nitrogen mixtures.

关键词： Nonequilibrium Plasmas Thermal Conductivity Propellant Chemical Kinetics Electric Propulsion simple algorithm Ohmic Heating Spectrometers Conservation Equations Activation Energy

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Finite volume multigrid method of the planar contraction flow of a viscoelastic fluid

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INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS 2001年第8期36卷 885-902页

作者： Al Moatssime, H Esselaoui, D Hakim, A Raghay, S Univ Cadi Ayyad Fac Sci & Tech Dept Maths Info Marrakech Morocco Univ Ibn Tofail Lab Sci Ingenieur Anal Numer & Optimisat Kenitra Morocco

This paper reports on a numerical algorithm for the steady flow of viscoelastic fluid. The conservative and constitutive equations are solved using the finite volume method (FVM) with a hybrid scheme for the velocities and first-order upwind approximation for the viscoelastic stress. A non-uniform staggered grid system is used. The iterative simple algorithm is employed to relax the coupled momentum and continuity equations. The non-linear algebraic equations over the flow domain are solved iteratively by the symmetrical coupled Gauss-Seidel (SCGS) method. In both, the full approximation storage (FAS) multigrid algorithm is used. An Oldroyd-B fluid model was selected for the calculation. Results are reported for planar 4:1 abrupt contraction at various Weissenberg numbers. The solutions are found to be stable and smooth. The solutions show that at high Weissenberg number the domain must be long enough. The convergence of the method has been verified with grid refinement. All the calculations have been performed on a PC equipped with a Pentium III processor at 550 MHz. Copyright (C) 2001 John Wiley & Sons, Ltd.

关键词： FAS multigrid algorithm FVM non-uniform staggered grid Oldroyd-B fluid simple algorithm

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Sensitivity of mixed subsonic-supersonic turbulent mixing layers

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JOURNAL OF PROPULSION AND POWER 2001年第4期17卷 823-835页

作者： Cottrell, DC Plesniak, MW Purdue Univ Sch Mech Engn Maurice J Zucrow Labs W Lafayette IN 47907 USA

Numerical predictions of compressible turbulent mixing layers have been performed for convective Mach numbers up to 0.7 (M-C less than or equal to0.7), This flow is particularly challenging to compute because the mixing layer consists of one supersonic stream and one subsonic stream, resulting in a mixed hyperbolic/elliptic solution. The FLUENT (C) computational fluid dynamics code, which incorporates a renormalization group k-is an element of turbulence model and the simpleC solution algorithm, was used to perform the computations. Initially, predictions were performed for several different convective Mach numbers (M-C = 0.2, 0.5, and 0.7), and the computed results (mixing layer thickness, mean velocity, and turbulence parameters) were compared with experiments to benchmark the code. Following this qualification procedure, the sensitivity of the Me = 0.7 case to disturbances was further investigated by introducing small perturbations to the boundary conditions and recomputing the mixing layer. Specifically, effects of perturbations to the secondary stream stagnation pressure and test section wall adjustment angle were investigated, It was found that the compressible mixing layer growth rate was significantly altered by small changes (<4%) in the secondary stream stagnation pressure. In addition, divergence or convergence of the test section walls of less than 3 deg resulted in appreciable changes in the streamwise pressure gradient and mixing layer development.

关键词： Turbulent Mixing Adverse Pressure Gradient simple algorithm Kinematic Viscosity Freestream Velocity Kinetic Energy Stress Distribution Solution algorithm Turbulence Models Turbulent Boundary Layer

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Natural convection in a trapezoidal enclosure with offset baffles

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JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER 2001年第2期15卷 212-218页

作者： Moukalled, F Acharya, S Amer Univ Beirut Dept Mech Engn Beirut Lebanon Louisiana State Univ Dept Mech Engn Baton Rouge LA 70803 USA

A numerical investigation has been made of natural convection heat transfer in a trapezoidal enclosure (representing attic spaces) with offset baffles. Two thermal boundary conditions representing summerlike conditions (upper surface heated) and winterlike conditions (upper surface cooled) and two baffle heights are studied. For each boundary condition and baffle height, two baffle positions are considered. In position I, the upper baffle is offset toward the heated vertical wall and the lower baffle is offset toward the symmetry plane of the enclosure, whereas in position II, the upper baffle is offset toward the symmetry plane and the lower baffle is offset toward the heated wall. Rayleigh number values range from 10(3) to 5 x 10(7) for summerlike conditions and from 10(3) to 10(6) for winterlike conditions. Predictions reveal a decrease in heat transfer in the presence of baffles. In winterlike conditions, convection starts to dominate at a Rayleigh number much lower than that in summerlike conditions. The maximum reduction in heat transfer is achieved with long baffles placed in position II for summerlike conditions and in position I for winterlike conditions. Average Nusselt number correlation for both boundary conditions are presented.

关键词： Natural Convection Thermal Boundary Condition Isotherms Conduction Vortices Thermal Conductivity simple algorithm Numerical Modeling Jet Stream Conservation Equations

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CFD development and simulation of flow fields in ventilated spaces with multiple occupants

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TRANSACTIONS OF THE ASAE 2001年第6期44卷 1839-1850页

作者： Wu, B Gebremedhin, KG Cornell Univ Biol & Environm Engn Dept Ithaca NY 14853 USA Tongji Univ Automobile Engn Dept Shanghai 200092 Peoples R China Cornell Univ Biol & Environm Engn Dept Ithaca NY USA

Simulation of flow fields in ventilated spaces with multiple occupants (cows) was conducted using a computational fluid dynamics (CFD) technique. Airflow in a ventilated space is affected by the locations of the inlet and outlet, inlet or room shape, and positions of the occupants. Three simulation test cases considered are: (1)four cows standing in a row with one end wall simulating as an inlet, and the opposite end wall simulating as an outlet;(2) four cows standing in a row with the two end walls simulating as inlets, and an outlet located at the center of the ceiling;and (3) ten cows placed at random with inlet and outlet arrangements the same as in Case (2). The body-fitted coordinate (BFC) system is adopted to characterize the shape of a cow, and the governing equations in the Cartesian coordinate system are transformed into the BFC system. To generate the grid under the BFC system, partial differential equations and algebraic interpolation methods were used The finite volume method is applied to transform the partial differential equations into algebraic ones, and the simple (Semi-Implicit Method for Pressure-Linked Equation) algorithm is extended to the BFC system to solve the flow field. The effects of obstructions (cows), and the positions of cows, inlets, and outlet on flow distribution were clearly demonstrated by velocity vectors, velocity profiles, and streamline plots generated. The flow field was more evenly distributed when cows were positioned at random than when in a row.

关键词： simulation CFD flow field ventilated space multi-occupant body-fitted coordinate system simple algorithm

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Numerical simulation of the cold flow in an axisymmetric non-compressing engine-like geometry

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INTERNATIONAL JOURNAL OF ENERGY RESEARCH 1999年第10期23卷 899-908页

作者： Bilgin, A Karadeniz Tech Univ Dept Mech Engn TR-61080 Trabzon Turkey

Fluid motion within the cylinder of a piston engine has a major influence on the performance of the engine. The general motion within the cylinder and the associated turbulence affect the charge stratification, combustion and heat transfer processes. In order to predict the charge stratification, one must understand and be able to predict the turbulent mixing processes (Reynolds, 1980). There are numerous alternative turbulence modelling approaches of varying degrees of complexity, but two of them, k-epsilon turbulence models and Reynolds stress models, are commonly used in engine modelling activities. In the present study, k-epsilon turbulence model was used to predict the how in the cylinder of a non-compressing engine-like configuration. Wall function treatment was employed in order to bridge the wall layer to the inner region. Finite volume method incorporated with hybrid (central/upwind) spatial and implicit temporal schemes, and simple algorithm (Patankar, 1980) were used to obtain numerical solutions. Results were compared with the measurements of Morse et al. (1978) and predictions of Gosman et al. (1980). Although the degree of agreement between the predictions and the measurements varies throughout the cycle and the flow field, the overall agreement is found to be satisfactory. Copyright (C) 1999 John Wiley & Sons, Ltd.

关键词： reciprocating engine flow k-epsilon turbulence model finite volume wall-functions simple algorithm

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Quantitative evaluation of flow computations by rainbow Schlieren deflectometry

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AIAA JOURNAL 1998年第11期36卷 1953-1960页

作者： Shenoy, AK Agrawal, AK Gollahalli, SR Univ Oklahoma Sch Aerosp & Mech Engn Norman OK 73019 USA

Rainbow schlieren deflectometry, a line-of sight optical measurement technique, was used to evaluate computations of steady nonreacting and reacting flows in axisymmetric systems. The nonreacting flow was that of an isothermal helium jet discharged vertically in air, and the reacting how was that of a hydrogen jet diffusion flame. The computed results were processed to obtain a color schlieren image for direct visual comparison with the corresponding experimental color schlieren image. The computed and measured angular deflections of light rays were also compared. In addition, the computed field distributions of scalar flow properties including the refractive index, species concentration, and temperature were compared quantitatively by inverting the experimental schlieren measurements, The results demonstrate the effectiveness of the rainbow schlieren technique in evaluating the physical models used for how computations.

关键词： Refractive Index Heat Transfer Thermal Diffusivity Kinematic Viscosity Schmidt Number simple algorithm Particle Image Velocimetry Laser Doppler Velocimetry Conservation Equations Chemical Equilibrium

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