Flow Rate Limitation of Steady Convective Dominated Open Capillary Channel Flows Through a Groove

An open capillary channel is a structure that establishes a liquid flow path when the capillary pressure caused by surface tension forces dominates in comparison to the hydrostatic pressure induced by gravitational or residual accelerations. To maintain a steady flow through the channel the capillar...

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Bibliographic Details
Published in:Microgravity science and technology 2010-04, Vol.22 (2), p.129-138
Main Authors: Haake, Dennis, Klatte, Joerg, Grah, Aleksander, Dreyer, Michael E.
Format: Article
Language:English
Subjects:
Aerospace Technology and Astronautics
Capillarity
Capillary pressure
Channels
Classical and Continuum Physics
Drop towers
Engineering
Flow rate
Flow rates
Free surfaces
Hydrostatic pressure
Ingestion
Liquids
Maximum flow
Original Article
Space Exploration and Astronautics
Space Sciences (including Extraterrestrial Physics
Steady flow
Surface tension
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Summary:An open capillary channel is a structure that establishes a liquid flow path when the capillary pressure caused by surface tension forces dominates in comparison to the hydrostatic pressure induced by gravitational or residual accelerations. To maintain a steady flow through the channel the capillary pressure of the free surface has to balance the pressure difference between the liquid and the surrounding constant pressure gas phase. Due to convective and viscous momentum transport the pressure along the flow path of the liquid decreases and causes the free surface to bend inwards. The maximum flow rate through the channel is reached when the free surface collapses and gas ingestion occurs near the outlet. This stability limit depends on the geometry of the channel and the properties of the liquid. In this paper we present an experimental setup which is used in the low-gravity environment of the Bremen Drop Tower. Experiments with convective dominated systems have been performed where the flow rate was increased up to the maximum value. In comparison to this we present a one-dimensional theoretical model to determine important characteristics of the flow, such as the free surface shape and the limiting flow rate. Furthermore we present an explanation for the mechanism of flow rate limitation for these flow conditions which is similar to the choking problem for compressible gas flows.
ISSN:0938-0108
1875-0494
DOI:10.1007/s12217-009-9164-2