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On the Spatio‐Temporal Flow Phenomena in Low Prandtl Number Melts Part 2: Shapes of the Interfaces and the Formation of Striations
Author(s) -
König F.,
Neumann W.
Publication year - 2001
Publication title -
crystal research and technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.377
H-Index - 64
eISSN - 1521-4079
pISSN - 0232-1300
DOI - 10.1002/1521-4079(200103)36:3<255::aid-crat255>3.0.co;2-9
Subject(s) - prandtl number , buoyancy , convection , thermal , mechanics , flow (mathematics) , temperature gradient , aspect ratio (aeronautics) , rayleigh number , materials science , chemistry , natural convection , thermodynamics , physics , meteorology , composite material
By marking the solid‐liquid interfaces during a stepwise decrease of the height of a stationary molten zone of Bi 05 Sb 15 Te 3 reasonable and changing curvatures of the interfaces are determined. In opposite to the lower interface the upper interface changes its shape from convex to concave for aspect ratios ar ≥2. The differences regarding the shape of both interfaces are indirectly due to the different flow intensities in both half zones. Furthermore, in addition to experiments described in Part 1 of this paper the molten zone was moved dynamically through the sample (zone melting). By estimating solutal and thermal Rayleigh numbers the solutal contribution to buoyancy convection is considered as negligible compared to the thermal part for the investigated zone heights. Time‐dependent convection during zone melting results in pronounced striations. With suitable models for the correlation between the oscillations of temperature, growth rate and microscopical concentration it was possible to estimate the shape and quantity of oscillating compositional inhomogeneities (striations).