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Proceedings Paper

Damping of unsteady flows in the physical vapor transport process
Author(s): Walter M. B. Duval; N. B. Singh; M. E. Glicksman
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Paper Abstract

The dynamics of the flow field during physical vapor transport of mercurous chloride is analyzed computationally for practical crystal growth conditions to distinguish between unsteady flow and thermal stress as the cause of crystal inhomogeneity. We analyze the flow field over the parametric range of 1.56 multiplied by 102 less than or equal to Ra less than or equal to 2.08 multiplied by 105, .011 less than or equal to Ar less than or equal to .112, and show that the effect of thermal stress as the cause of crystal inhomogeneity can be investigated by performing experiments with low aspect ratio enclosures for Ar less than .028 and Ra less than 2.4 multiplied by 103 for which the flow becomes diffusive-advective. Dynamical characteristics of the flow field indicate a transition from chaotic flow Ra equals 2.08 multiplied by 105 to steady flow Ra less than 1.4 multiplied by 104 occurs through period doubling. A microgravity environment can be used effectively to grow high quality crystals, if thermal stresses are not the cause of crystal inhomogeneity, since unsteady flows are damped regardless of the aspect ratio of the enclosure.

Paper Details

Date Published: 7 July 1997
PDF: 11 pages
Proc. SPIE 3123, Materials Research in Low Gravity, (7 July 1997); doi: 10.1117/12.277721
Show Author Affiliations
Walter M. B. Duval, NASA Lewis Research Ctr. (United States)
N. B. Singh, Northrop Grumman Corp. (United States)
M. E. Glicksman, Rensselaer Polytechnic Institute (United States)

Published in SPIE Proceedings Vol. 3123:
Materials Research in Low Gravity
Narayanan Ramachandran, Editor(s)

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