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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 5 (1993), S. 2610-2623 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: For many materials processing techniques, the meniscus of liquid bridging the crystal to the melt is critical in determining the properties of the solidified crystal. It is standard practice for existing theoretical models to use equilibrium meniscus shapes with specified contact angle to represent the behavior of the meniscus. It is shown here that with such boundary conditions, multiple solutions exist to the axisymmetric form of the Laplace–Young equation. Furthermore, these possible meniscus profiles may, depending on the interaction of Bond number, pressurization, aspect ratio and contact angle, correspond to minima, maxima or nonextrema points, as far as energy is concerned. The implications of this observation on meniscus stability are explored. The effect of direction of pulling in relation to gravity is also investigated. It appears that for tall menisci, commonly adopted equilibrium shapes may be unstable and the consequent dynamic behavior must be considered. Quasiequilibrium dynamics of the meniscus is simulated using a simplified hysteresis model for the contact angle at the top of the meniscus. A variety of behavior is found to arise, which is not fully captured by relations governing meniscus behavior used hitherto in many theoretical simulations.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Computational mechanics 9 (1992), S. 285-304 
    ISSN: 1432-0924
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract For the time dependent flow simulation, despite the existence of extensive literature dealing with either the convection or the unsteady terms, their interaction has not been adequately investigated. In order to shed more light on this important issue, three time stepping methods, including the first-order backward Euler scheme, the second-order Crank-Nicolson scheme, and the third-order Adams-Bashforth/Adams-Moulton predictor-corrector scheme are studied along with four convection schemes, including the first-order upwind, the second-order upwind, the second-order central differencing, and QUICK schemes. The Burgers equation of both linear and nonlinear forms is used as the test problem, aided by the von Neumann stability analysis and the FFT spectral analysis. The results indicate that a second-or higher-order accuracy for both time and space discretizations can produce satisfactory results for smooth solution profiles. Overall, among the schemes tested, either a combination of first-order upwind for convection and Crank-Nicolson for time, or a combination of second-order upwind for convection and backward Euler for time performs better. It appears that by selectively utilizing the dispersive and diffusive characteristics of the time stepping and convection schemes in complementary manners, overall accuracy can be improved.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 12 (1991), S. 143-160 
    ISSN: 0271-2091
    Keywords: Adaptive grid computation ; Natural convection ; Navier-Stokes flow ; Curvilinear coordinates ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A three-dimensional model has been developed to compute the thermofluid transport within a discharge arctube. The model has proved very useful for guiding the choice of design parameters to optimize the lamp performance. However, uncertainties exist with respect to quantitative aspects of the physical model, especially those related to radiation heat transfer. In the present work a grid refinement procedure and an adaptive grid method are used to improve the quantitative accuracy of the model and to help improve the physical modelling. The adaptive grid method, based on the multiple one-dimensional equidistribution concept, can responsively redistribute the grids to optimize the grid resolutions. Adaptive grid solutions modify the predicted maximum gas temperature, the buoyancy-induced convection strength, the location of the high-temperature core, and the wall temperature profiles. The adaptive grid solutions show more consistent trends when compared to the measurements. On the basis of the quantitatively more definite information, adjustments can be made with regard to the uncertainties of the physical model.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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