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Critical point wetting drop tower experimentThe 100 m Drop Tower at NASA-Marshall was used to provide the step change in acceleration from 1.0 to 0.0005 g. An inter-fluid meniscus oscillates vertically within a cylindrical container when suddenly released from earth's gravity and taken into a microgravity environment. Oscillations damp out from energy dissipative mechanisms such as viscosity and interfacial friction. Damping of the oscillations by the later mechanism is affected by the nature of the interfacial junction between the fluid-fluid interface and the container wall. In earlier stages of the project, the meniscus shape which developed during microgravity conditions was applied to evaluations of wetting phenomena near the critical temperature. Variations in equilibrium contact angle against the container wall were expected to occur under critical wetting conditions. However, it became apparent that the meaningful phenomenon was the damping of interfacial oscillations. This latter concept makes up the bulk of this report. Perfluoromethyl cyclohexane and isopropanol in glass were the materials used for the experiment. The wetting condition of the fluids against the wall changes at the critical wetting transition temperature. This change in wetting causes a change in the damping characteristics of the interfacial excursions during oscillation and no measurable change in contact angle. The effect of contact line friction measured above and below the wetting transition temperature was to increase the period of vertical oscillation for the vapor-liquid interface when below the wetting transition temperature.
Document ID
19900011892
Acquisition Source
Legacy CDMS
Document Type
Contractor Report (CR)
Authors
Kaukler, William F.
(Alabama Univ. Huntsville, AL, United States)
Date Acquired
September 6, 2013
Publication Date
April 18, 1990
Subject Category
Materials Processing
Report/Patent Number
NASA-CR-186513
NAS 1.26:186513
Accession Number
90N21208
Funding Number(s)
CONTRACT_GRANT: NAG8-511
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
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