(497c) Multiscale Modeling of Two-Phase Flow Through Microtechnology Based Devices With Complex Geometries

Multiscale
Modeling of Two-Phase Flow through Microtechnology Based Devices with Complex
Geometries

Agnieszka Truszkowska, Frederick Atadanaand
Goran Jovanovic

Oregon State University, School of Chemical, Biological,
and Environmental Engineering, Corvallis, OR 97330, USA

Emails: truszkoa@onid.orst.edu, atadanaf@onid.orst.edu, goran.jovanovic@oregonstate.edu

Bubble management is one of the
key challenges in development of many microtechnology-based processes. The presence
of a discrete gas phase (bubbles) in a continuous liquid phase flow provides
opportunities for advanced design of microtechnology-based devices; but also,
causes side effects which alter device performance or even set off device
dysfunctionallity. Prevention of entering or generation of gas bubbles in
microscale-based devices could be a difficult task; hence, more often effort is
shifted towards efficient management of flow of bubbles already present in the
system.

In this paper we focus our
attention on a two-phase system in which gas phase bubbles may be deliberately
introduced to provide (for example): reactants in microreactors, oxygen in
bioreactors, or a phase carrier for separation operations. Our work also includes
optimization of device architecture, a process based on numerical simulation. Devices
with complex micro/nano-features very often enable designs with substantial potential
for successful management of a two-phase flow. A 3D simulation of a two-phase
flow is computationally intensive, due to a large resolution requirement, which
imposes limitations in computational exploration and improvement of device
design.

In this paper we propose a novel multiscale
modeling approach in describing a two-phase flow with discreet gas phase (bubbles)
pertinent for microscale devices with complex structural features. Our effort
is focused on the management of bubble motion (velocity, residence time,
acceleration), which is influenced by the internal structure of a
microscale-based device. We are using a two-dimensional Lattice Boltzmann modeling
approach to develop an appropriate forcing function term which acts on bubble
interface and effectively accelerates, redirects, or blocks bubble motion.  This
forcing term serves as an ?information carrier? between lower scale with
distinct micro-features and upper, geometrically homogeneous scale. The forcing
term reflects bubble curvature, contact angles and resulting pressure
distribution due to interactions with detailed geometry of the microscale-based
device. In the ?upper? scale bubble shape is partially transformed but the effective
movement of bubbles is preserved from the ?lower? scale.

Finally, we demonstrate a
possible design optimization approach for microscale devices with microposts.
Based on experimentally observed bubble behavior in a liquid flow with force
field acting on the bubble interface we numerically produced different gas
phase (bubble) retention patterns leading to preliminary conclusions about size
and distribution of microscale features in the simulated device.