Graduate Thesis Or Dissertation

 

Multiscale modeling of two-phase flows in microarchitectures with microfeatures Public Deposited

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/5q47rt56m

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  • Two-phase flows in microtechnology based devices are purposefully present in multiphase reactors, phase separators, analytical devices and others. Two-phase flows can also be an undesirable side effect occurring during operation due to phase transitions or, more commonly, introduction of surrounding air through equipment gaps and with process feed. In both cases, the two phases require control to achieve desired system performance. Devices with microfeatures such as posts and pillars represent relatively unexplored design direction with the potential for successful fulfillment of various multi-phase flows objectives. Efficient design of microfeatured devices requires computational tools. However, the importance of two-phase interface physics imposes high resolution computing, which when combined with usual microtechnology high-aspect ratios results in large computational efforts. Multiscale modeling provides a means for preserving accuracy while lowering computational costs. This thesis proposes a novel multiscale modeling approach for modeling microarchitectures with microfeatures. The main idea of the approach is to enable numerical simulations of two-phase flows in microfeatured architectures without resolving the actual microfeatures. Effect of microfeatures presence is incorporated through a coupling operator, vector, or scalar field. Removal of microfeatures allows for modeling with significantly coarser computational grids with grid size being limited by the smallest droplet sizes. Multiscale modeling approach is accompanied by a piecewise modeling concept in which characterization of the entire microarchitecture is performed with smaller, and hence computationally less intensive, representative domains. Piecewise modeling can be used as a replacement for full-size architecture simulations in multiscale modeling but can also serve as an independent modeling tool. The basic framework of the proposed approach is developed based on the example of droplet retention times in microfeatured architectures. This approach is successfully incorporated into Shan and Chen Lattice Boltzmann method, validated and applied to three different architectures. Demonstrated are the capabilities and challenges of the proposed multiscale modeling approach. Viability and potential improvements of piecewise modeling are also confirmed.
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