(509g) Lattice Boltzmann Method Based Multiscale Modeling of Two-Phase Flows through Microarchitectures with Microfeatures

Lattice Boltzmann
Method based multiscale modeling of two-phase flows through
microarchitectures with microfeatures

Agnieszka Truszkowska¹
and Goran Jovanovic¹

¹Oregon
State University, Department of Chemical, Biological, and
Environmental Engineering, Corvallis, OR 97330, USA 

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

Segmented
two-phase flows in microscale-based structures display attractive
characteristics such as enhanced mixing and intensification of mass
and heat transfer, reduced Taylor dispersion, and opportunity to
control and manipulate dispersed phase; bubbles or droplets.
Two-phase flow in microscale-based structures is commonly used in
emulsification and encapsulation operations, microreactors, material
synthesis, bioassays and many other applications ([1],[2]). Apart for
its purposeful presence, dispersed phase could occur in
microarchitectures as a side effect emerging from phase transition,
inadvertent inflow with process feed, or through equipment gaps
([3],[4]). Whether part of an intended operation or unwanted
operating byproduct, second/discrete phase has to be properly
controlled to achieve desired system performance.

Optimization of two-phase processes
on microscale level results in numerous opportunities related to both
operating conditions and design architecture. However, efficient and
comprehensive optimization often requires recurring use of numerical
models in addition to experimental data. Additionally, these
computational models require high resolution computing due to
dominant interfacial transport phenomena. Due to the need for
excessive computational resources many researchers reduce modeling
effort to a representative small segment of the system, or make
overly simplifying assumptions and approximations.

In this paper we present a novel,
multiscale-modeling approach for numerical representation of the
two-phase flow in microscale-based structures containing micro
features such as posts and pillars. Microscale-based architectures
containing various micro features are relatively unexplored design
options ([5], [6]) with vast potential for optimization due to their
extreme design flexibility. We explore their characteristics and
provide a novel multiscale modeling approach within the framework of
Shan and Chen Lattice Boltzmann modeling method.

Example used in the numerical
experiments is an array of cylindrical micropillars with staggered,
equilateral arrangement. A multiscale operator in the form of field
of discrete vector quantities, forcing terms, is developed. Discrete
vector forcing terms are applied on the interface of the dispersed
phase, which results in an equivalent average behavior of the
dispersed phase in the geometrically simplified scale, just as in the
geometrically fully resolved scale. We present several variations of
the operator as well as its characteristics and robustness. Finally,
we discuss applicability and limitations of the approach based on
model system simulations and classical benchmark cases.

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[2] Gunther, Axel, and Klavs F.
Jensen, "Multiphase microfluidics: from flow characteristics to
chemical and materials synthesis", Lab on a Chip, 6,12 (2006):
1487-1503

[3] Jensen, Mads Jakob, Goran
Goranovic, and Henrik Bruus, "The clogging pressure of bubbles
in hydrophilic microchannel contractions", Journal of
Micromechanics and Microengineering, 14,7 (2004): 876

[4] Litterst, C., et al., "Improved
gas bubble mobility in CHIC-type flow channels", Actuator, Messe
Bremen, Germany (2004): 541-544

[5] Krishnamurthy, Santosh, and Yoav
Peles, "Gas-liquid two-phase flow across a bank of
micropillars", Physics of Fluids 19 (2007): 043302

[6] De Loos, S. R. A., et al.
"Gasâ??liquid dynamics at low Reynolds numbers in pillared
rectangular micro channels", Microfluidics and nanofluidics, 9,1
(2010): 131-144