The rise velocity of injected air phase from the injection point toward the
vadose zone is a critical factor in in-situ air sparging operations. It has been
reported in the literature that air injected into saturated gravel rises as discrete air
bubbles in bubbly flow of air phase. The objective of this study is to develop a
quantitative technique to estimate the rise velocity of an air bubble in coarse
porous media. The model is based on the macroscopic balance equation for forces
acting on a bubble rising in a porous medium. The governing equation
incorporates inertial force, added mass force, buoyant force, surface tension and
drag force that results from the momentum transfer between the phases. The
momentum transfer terms take into account the viscous as well as the kinetic
energy losses at high velocities. Analytical solutions are obtained for steady,
quasi-steady, and accelerated bubble rise velocities. Results show that air bubbles
moving up through a porous medium equilibrate after a short travel time and very
iv
short distances of rise. It is determined that the terminal rise velocity of a single
air bubble in an otherwise water saturated porous medium cannot exceed 18.5
cm/sec. The theoretical model results compared favorably with the experimental
data reported in the literature. A dimensional analysis conducted to study the
effect of individual forces indicates that the buoyant force is largely balanced by
the drag force for bubbles with an equivalent radius of 0.2-0.5 cm. With
increasing bubble radius, the dimensionless number representing the effect of the
surface tension force decreases rapidly. Since the total inertial force is quite small,
the accelerated bubble rise velocity can be approximated by the terminal velocity.
| Identifer | oai:union.ndltd.org:METU/oai:etd.lib.metu.edu.tr:http://etd.lib.metu.edu.tr/upload/12604709/index.pdf |
| Date | 01 January 2004 |
| Creators | Cihan, Abdullah |
| Contributors | Corapcioglu, Mehmet Yavuz |
| Publisher | METU |
| Source Sets | Middle East Technical Univ. |
| Language | English |
| Detected Language | English |
| Type | M.S. Thesis |
| Format | text/pdf |
| Rights | To liberate the content for public access |
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