A Flexible OpenFOAM-Based Simulation Framework for Multiphase Flow in Microsystems

In complex fluidic microsystems, such as microreactors, relevant transport phenomena frequently occur across multiple coupled length scales, from nanometer-scale interfacial reactions to micro-scale transport within porous structures and microchannels, up to millimeter-scale fluid distribution networks. Because these devices often involve multiphase conditions, processes such as reaction rates, heat release, species transport, and the formation of bubbles or droplets are tightly coupled in an inherently unsteady and three-dimensional manner. To simplify the simulation and analysis of these fluidic processes, we propose multiMultiFoam, a flexible, strongly object-oriented framework based on the open-source software OpenFOAM. The framework is explicitly designed to be easily extendable with respect to modeling physical behavior, solving transport equations, and adapting numerical solution strategies, and it bridges various length scales within a single, unified environment. Users can flexibly decide which regions of a microfluidic device require a fully resolved simulation approach and which can be efficiently approximated using specialized models; for example, flow through porous transport layers can be explicitly resolved at the micro-scale or modeled using a homogenized Darcy approach. ... mehrThe framework interfaces allow the inclusion of specialized third-party software, such as the Volume-of-Fluid library TwoPhaseFlow and the GeoChemFoam library for reactive transport within pore-scale geometries. We present the core architecture of the framework, strategies for integrating third-party code without reimplementation, and computational case studies including multiphase flows across multiscale geometries, porous media modeling with a hybrid VoF-Darcy approach, and continuous flow reactions.