Viscosity measurement using drop coalescence in microgravity

We present in here validation studies of a new method for application in microgravity environment which measures the viscosity of highly viscous undercooled liquids using drop coalescence. The method has the advantage of avoiding heterogeneous nucleation at container walls caused by crystallization...

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Bibliographic Details
Published in:Microgravity science and technology 2003-03, Vol.14 (1), p.9-19
Main Authors: Antar, Basil N., Ethridge, Edwin C., Maxwell, Daniel
Format: Article
Language:English
Subjects:
Coalescence
Coalescing
Computation
Crystallization
Design engineering
Experiments
Free surfaces
High speed photography
Liquids
Microgravity
Microgravity applications
Nucleation
Relaxation time
Surface tension
Surface velocity
Validation studies
Viscosity
Viscosity measurement
Weightlessness
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Summary:We present in here validation studies of a new method for application in microgravity environment which measures the viscosity of highly viscous undercooled liquids using drop coalescence. The method has the advantage of avoiding heterogeneous nucleation at container walls caused by crystallization of undercooled liquids during processing. Homogeneous nucleation can also be avoided due to the rapidity of the measurement using this method. The technique relies on measurements from experiments conducted in near zero gravity environment as well as highly accurate analytical formulation for the coalescence process. The viscosity of the liquid is determined by allowing the computed free surface shape relaxation time to be adjusted in response to the measured free surface velocity for two coalescing drops. Results are presented from two sets of validation experiments for the method which were conducted on board aircraft flying parabolic trajectories. In these tests the viscosity of a highly viscous liquid, namely glycerin, was determined at different temperatures using the drop coalescence method described in here. The experiments measured the free surface velocity of two glycerin drops coalescing under the action of surface tension alone in low gravity environment using high speed photography. The liquid viscosity was determined by adjusting the computed free surface velocity values to the measured experimental data. The results of these experiments were found to agree reasonably well with the known viscosity for the test liquid used.
ISSN:0938-0108
1875-0494
DOI:10.1007/BF02873332