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Effects of Gravity on Bubble Formation at a Plate OrificeA model of the dynamic regime of gas injection through a submerged plate orifice into an ideally wetting liquid is developed in the circumstance when successively detached bubbles may be regarded as independent objects. Two major factors favor bubble detachment: the buoyancy force and a force due to the momentum inflow into the bubble with injected gas. In normal and moderately reduced gravity, the first factor dominates. At relatively low flow rates, a growing bubble is modeled as a spherical segment touching the orifice perimeter during the whole period of its evolution till detachment. If the flow rate exceeds a critical value, another stage of bubble evolution occurs in which an almost spherical gas envelope is connected with the orifice by a nearly cylindrical gaseous stem that lengthens as the bubble rises above the plate. The bubble continues to grow until the gas supply through the stem is completely cut off, after which back flow of gas into the stem from the bubble becomes possible. In microgravity, the second factor prevails, and the latter stage is always present irrespective of the flow rate. However, the gas envelope rises and the stem lengthens very slowly. This difference in the underlying physical mechanisms provides for key properties of bubble growth and detachment being drastically different in appreciable and sufficiently reduced gravity. The frequency of bubble formation slightly decreases with and the detachment volume is almost proportional to the gas flow rate in the first case, in accordance with familiar relations. In the second case, the first variable is proportional to the flow rate whereas the second one is independent of it. Effects of other parameters, such as the orifice radius, gas and liquid densities, and surface tension are discussed.
Document ID
20020014840
Acquisition Source
Ames Research Center
Document Type
Conference Paper
Authors
Webbon, Bruce W.
(NASA Ames Research Center Moffett Field, CA United States)
Buyevich, Yu A.
(National Academy of Sciences - National Research Council Moffett Field, CA United States)
Date Acquired
August 20, 2013
Publication Date
January 1, 1995
Subject Category
Fluid Mechanics And Thermodynamics
Meeting Information
Meeting: Fluid Engineering Conference
Location: Hilton Head, SC
Country: United States
Start Date: August 13, 1995
End Date: August 18, 1995
Sponsors: American Society of Mechanical Engineers, Japan Society of Mechanical Engineers
Funding Number(s)
PROJECT: RTOP 199-61-62
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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