There are many options available when selecting a computational model for
two-phase flows. It is important to understand all the features of the model
selected, including when the model is appropriate and how using it may affect
your results. This work examines how volume displacement effects in two-phase
Eulerian-Lagrangian models manifest themselves. Some test cases are examined
to determine what input these effects have on the flow, and if we can predict
when they will become important. Bubble injection into a traveling vortex ring is
studied in-depth, as it provides significant insight into the physics of these
volume displacement effects. When a few bubbles are entrained into a traveling
vortex ring, it has been shown that even at extremely low volume loadings, their
presence can significantly affect the structure of the vortex core (Sridhar & Katz
1999). A typical Eulerian-Lagrangian point-particle model with two-way coupling
for this dilute system, wherein the bubbles are assumed subgrid and momentum
point-sources are used to model their effect on the flow, is shown to be unable to
accurately capture the experimental trends of bubble settling location, bubble
escape, and vortex distortion for a range of bubble parameters and vortex
strengths. Accounting for fluid volume displacement due to bubble motion, using
a model termed as volumetric coupling, experimental trends on vortex distortion
and bubble settling location are well captured. The fluid displacement effects are
studied by introducing the notion of a volume displacement force, the net force
on the fluid due to volumetric coupling, which is found to be dominant even at
the low volume loadings investigated here. A method of quantifying of these
forces is derived and used to study the effects for a wide range of particle to
fluid density ratios in Taylor-Green vortices. A simple modification to the standard
point-particle Lagrangian approach is developed, wherein the interphase reaction
source terms are consistently altered to account for the fluid displacement effects
and reactions due to bubble accelerations. / Graduation date: 2013 / Access restricted to the OSU Community at author's request from Sept. 24, 2012 - Sept. 24, 2013
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/33789 |
| Date | 24 September 2013 |
| Creators | Cihonski, Andrew John |
| Contributors | Apte, Sourabh |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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