On the limitation imposed by gravity on measurements of the critical viscosity of a pure fluid


  • Richard A. Ferrell,

    1. Theoretische Physik, Physik-Department der Technischen Universität München, D-85747 Garching bei München, Germany
    2. Center for Theoretical Physics of the Department of Physics, University of Maryland, College Park, Maryland 20742, USA
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  • Michael R. Moldover

    1. Thermophysics Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
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Measurements of the viscosity of a fluid by means of a parallel plate torsional oscillator are conventionally limited to a plate separation that is much larger than the viscous penetration depth of the fluid contained between the plates. Here we demonstrate that, in principle, useful measurements can be carried out in the opposite regime where the thickness is smaller than the penetration depth. An alternative method, described in the last part of this paper, for alleviating the restriction imposed by the density stratification that results from the earth's gravity, is to use electrostriction, rather than the inertial force, to drive the fluid between the plates.