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Local and Global Bifurcations of Flow Fields During Physical Vapor Transport: Application to a Microgravity ExperimentThe local bifurcation of the flow field, during physical vapor transport for a parametric range of experimental interest, shows that its dynamical state ranges from steady to aperiodic. Comparison of computationally predicted velocity profiles with laser doppler velocimetry measurements shows reasonable agreement in both magnitude and planform. Correlation of experimentally measured crystal quality with the predicted dynamical state of the flow field shows a degradation of quality with an increase in Rayleigh number. The global bifurcation of the flow field corresponding to low crystal quality indicates the presence of a traveling wave for Ra = 1.09 x 10(exp 5). For this Rayleigh number threshold a chaotic transport state occurs. However, a microgravity environment for this case effectively stabilizes the flow to diffusive-advective and provides the setting to grow crystals with optimal quality.
Document ID
19970009621
Document Type
Conference Paper
Authors
Duval, W. M. B. (NASA Lewis Research Center Cleveland, OH United States)
Singh, N. B. (Northrop Grumman Corp. Pittsburgh, PA United States)
Glicksman, M. E. (Rensselaer Polytechnic Inst. Troy, NY United States)
Date Acquired
September 6, 2013
Publication Date
December 1, 1996
Subject Category
Materials Processing
Report/Patent Number
E-10541
NAS 1.15:107372
NASA-TM-107372
Meeting Information
American Conference on Crystal Growth(Vail, CO)
Funding Number(s)
PROJECT: RTOP 962-20-00
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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