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Research Containing: Wetting

Capillary Wetting Analysis of the CFE-Vane Gap Geometry

by on 9 June 2015in Physical Sciences No comment

The Vane Gap Capillary Flow Experiments are part of a suite of low-g experiments flown onboard the International Space Station to observe critical wetting phenomena in ‘large length scale’ capillary systems. The Vane Gap geometry consists of a right cylinder with elliptic cross-section and a single central vane that does not contact the container walls. The vane is slightly asymmetric so that two gaps between the vane and container wall are not of the same size. In this study, we identify the critical wetting conditions of this geometry using the Concus-Finn method for both perfectly and partially wetting fluids as a function of container asymmetry. In a cylindrical container in zero-g, single-valued finite height equilibrium capillary surfaces fail to exist if a critical wetting condition is satisfied. This nonexistence results in significant redistribution of the fluids in the container. It will be shown that there could be three critical geometric wetting conditions that include one in each gap region and one for a global shift of bulk fluid which, among the three, is the most significant.

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Geometry Pumping on Spacecraft (The CFE-Vane Gap Experiments on ISS)

by on 9 June 2015in Physical Sciences No comment

urrent experiments aboard the International Space Station (ISS) illustrate an extent to which liquid behavior aboard spacecraft can be controlled by wetting and container geometry. The experiments are referred to as the 'Vane-Gap' experiments and are part of a more general set of simple handheld Capillary Flow Experiments1) (CFE) designed and developed at NASA's Glenn Research Center for conduct on ISS. The CFE-Vane Gap experiments highlight the sensitivity of a capillary fluid surface to container shape and how small changes to said shape may result in dramatic global shifts of the liquid within the container. Understanding such behaviors is central to the passive management of liquids aboard spacecraft and in certain cases permits us the ability to move (pump) large quantities (potentially tons) of liquid by a simple choice of container shape. In particular, the Vane-Gap experiments identify the critical geometric wetting conditions of a vane structure that does not quite meet the container wall-a construct arising in various fluid systems aboard spacecraft such as liquid fuel and cryogen storage tanks, thermal fluids management, and water processing equipment. In this paper experimental results are compared with preliminary theoretical and numerical analyses.

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