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Critical Velocities in Open Capillary FlowThis paper describes the proposed research program on open capillary flow and the preliminary work performed theoretically and in drop tower experiments. The work focuses on the fundamental physical understanding of the flow through capillary bound geometries, where the circumference of the cross section of the flow path contains free surfaces. Examples for such a flow configuration are capillary vanes in surface tension tanks, flow along edges and corners and flow through liquid bridges. The geometries may be classified by their cross section areas, wetted circumferences and the radii of curvature of the free surfaces. In the streaming float zone the flow path is bound by a free surface only. The ribbon vane is a model for vane types used in surface tension tanks, where a structure in proximity to the tank wall forms a capillary gap. A groove is used in heat pipes for the transportation of the condensed working fluid to the heat source and a wedge may occur in a spaceborne experiment where fluid has to be transported by the means of surface tension. The research objectives are the determination of the maximum volume flux, the observation of the free surfaces and the liquid flow inside the flow path as well as the evaluation of the limiting capillary wave speed. The restriction of the maximum volume flux is due to convective forces (flow velocity exceeding the capillary wave speed) and/or viscous forces, i.e. the viscous head loss along the flow path must be compensated by the capillary pressure due to the curved free surface. Exceeding the maximum volume flux leads to the choking of the flow path, thus the free surface collapses and.gas ingestion occurs at the outlet. The means are ground-based experimental work with plateau tanks and in a drop tower, a sounding rocket flight, and theoretical analysis with integral balances as well as full three dimensional CFD solutions for flow with free surfaces.
Document ID
19970000460
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Dreyer, Michael (Bremen Univ. Germany)
Langbein, Dieter (Bremen Univ. Germany)
Rath, Hans J. (Bremen Univ. Germany)
Date Acquired
August 17, 2013
Publication Date
September 1, 1996
Publication Information
Publication: Third Microgravity Fluid Physics Conference
Subject Category
Fluid Mechanics And Heat Transfer
Accession Number
97N10427
Funding Number(s)
CONTRACT_GRANT: DARA-50-WM-9432
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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