388856 Lattice Boltzmann Method Based Multiscale Modeling of Two-Phase Flows through Microarchitectures with Microfeatures

Wednesday, November 19, 2014: 2:18 PM
401 - 402 (Hilton Atlanta)
Agnieszka Truszkowska, Oregon State University, Corvallis, OR and Goran Jovanovic, School of Chemical, Biological, and Environmental Engineering, Oregon State University, Corvallis, OR

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.

[1] Shui, Lingling, Jan CT Eijkel, and Albert van den Berg, "Multiphase flow in microfluidic systems--Control and applications of droplets and interfaces", Advances in Colloid and Interface Science, 133,1 (2007): 35-49

[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. "Gas--liquid dynamics at low Reynolds numbers in pillared rectangular micro channels", Microfluidics and nanofluidics, 9,1 (2010): 131-144


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