### MICHAEL MANGA: Recent Refereed Publications

## Abstracts

#### Stark, J and M. Manga, The Motion of long bubbles in a network of tubes,
*Transport in Porous Media*, vol. 40, 201-218.

Abstract:

The motion and interaction of discrete bubbles in porous materials
is studied numerically using a network model.
The goal is to extend analytical results for
the motion of bubbles through
a single straight tube to a more ``realistic'' geometry for
porous materials, modeled
here as a planar network of straight
tubes of different radii. The problem is characterized by two dimensionless
parameters, the Capillary number (Ca) and the volume fraction of
bubbles (phi); results are characterized by determining the
effective permeability of the network
and the mean residence time of bubbles
in the material.
The simulations indicate that at low volume fraction
most of the bubbles
follow a limited number of high-flow pathways through the network. In this
case the predictions of our simulations can be approximated by a simple
analytical model.
Bubbles interact with each other because their presence changes
the local resistance to flow in individual tubes.
As phi increases,
interactions between individual bubbles become important
resulting in a wider range of mean residence times
in the porous material.

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