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Marcello Lappa^{1, 2}
FDMP-Fluid Dynamics & Materials Processing, Vol.1, No.1, pp. 1-20, 2005, DOI:10.3970/fdmp.2005.001.001
Abstract Possible natural transport mechanisms in cubical and shallow cavities with different heating conditions (from below or from the side) are investigated by means of numerical solution of the non-linear model equations and multiprocessor computations. Attention is focused on a variety of three-dimensional steady effects that can arise in such configurations in the case of low-Pr liquids (silicon melt) even for relatively small values of the temperature gradient due to localized boundary effects and/or true instabilities of the flow. Such aspects are still poorly known or completely ignored owing to the fact that most of the existing experiments focused on the… More >

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1093

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A.Yu. Gelfgat¹, A. Rubinov², P.Z. Bar-Yoseph², A. Solan²
FDMP-Fluid Dynamics & Materials Processing, Vol.1, No.1, pp. 21-32, 2005, DOI:10.3970/fdmp.2005.001.021
Abstract The three-dimensional instability of the thermocapillary convection in cylindrical undeformable floating zones heated laterally is studied numerically. Different types of the boundary conditions, including radiation heating, linearized radiation and prescribed heat flux are used in the calculation. Stability diagrams showing the Prandtl number dependence of the critical Marangoni numbers that represent the thermocapillary forcing for different heating conditions are reported. It is shown that the primary instability of initially axisymmetric thermocapillary flows is defined mainly by the total amount of heat supplied through the heated side surface. The way in which the heat is supplied has a less significant effect… More >

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934

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C. W. Lan¹, B. C. Yeh
FDMP-Fluid Dynamics & Materials Processing, Vol.1, No.1, pp. 33-44, 2005, DOI:10.3970/fdmp.2005.001.033
Abstract The suppression of unstable Marangoni convection in floating-zone crystal growth by magnetic fields has enjoyed over recent years a widespread use as a reliable and useful strategy. A transversal direction of the field is particularly efficient, but asymmetric zone shapes and thus segregation are induced. Counter-rotation of the feed and of the crystal rods is a common way to improve dopant homogeneity. However, its effects under magnetic fields are complex and have not yet been studied in detail. In the present analysis, three-dimensional (3D) simulations based on a finite-volume/multigrid method are used to illustrate the effects of rotation on the… More >

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1071

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T. Tsukada¹, M. Kobayashi², C. J. Jing³, N. Imaishi⁴
FDMP-Fluid Dynamics & Materials Processing, Vol.1, No.1, pp. 45-62, 2005, DOI:10.3970/fdmp.2005.001.045
Abstract In this paper, our recent numerical studies on the Czochralski (CZ) crystal growth of oxide are surveyed. In the first part of the analysis, a "global" heat transfer model for an inductively heated CZ furnace is introduced and depicted in detail. It is emphasized that accounting for the internal radiation within the crystal and/or melt is of crucial importance since they are often semitransparent to infrared radiation. Results coming from such a "global" approach suggest that the melt/crystal interface shape is strongly affected by the optical properties of the crystal, of the melt and by the melt convection. The second… More >

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1106

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Asghar Esmaeeli¹
FDMP-Fluid Dynamics & Materials Processing, Vol.1, No.1, pp. 63-80, 2005, DOI:10.3970/fdmp.2005.001.063
Abstract We use direct numerical simulations to study phase distribution of bubbles under terrestrial and microgravity conditions. The full Navier-Stokes and energy equations, for the flows inside and outside the bubbles, are solved using a front tracking/finite difference technique. Both nearly spherical and deformable bubbles are considered. For buoyancy-driven flows, spherical bubbles at Re = O(10) and deformable ones at Re = O(100) exhibit a uniform spatial distribution at quasi steady-state conditions, while nearly spherical bubbles at Re = O(100) form horizontal rafts. Bubbles, driven by thermocapillary effects in microgravity, also form horizontal rafts, but due to an entirely different mechanism.… More >

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979

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Gustav Amberg¹, Junichiro Shiomi²
FDMP-Fluid Dynamics & Materials Processing, Vol.1, No.1, pp. 81-96, 2005, DOI:10.3970/fdmp.2005.001.081
Abstract A few issues in materials science are reviewed with regard to the importance of fluid flows. The effect of convection on generic solidification problems is discussed. One relevant class of flows in melts is those driven by surface tension gradients. In welding this thermo- or solutocapillary flow will determine the penetration depth, and will depend very sensitively on the composition of the material, through the dependence of surface tension on temperature, presence of surfactants, etc. In crystal growth the convective motion in the melt may cause instabilities that are often undesired in practical processes. The unsteady flow structure can cause… More >

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