Title:
Modeling moderately dense to dilute multiphase reacting flows
Modeling moderately dense to dilute multiphase reacting flows
Author(s)
Panchal, Achyut
Advisor(s)
Menon, Suresh
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Abstract
Computational modeling of multiphase flows consists of two broader sets of methods: resolved approaches where the multiphase entities (MPE) are larger and resolved on the computational grid, and dispersed approaches where the MPEs are relatively small and not resolved on the grid but they are treated as point-particles that interact with the background continuum. A consistent multiphase formulation is developed in this work that can be used to model either resolved or unresolved MPEs over a complete range of volume fractions. One phase is always modeled as a continuum Eulerian phase, whereas the other phase is modeled either as a continuum Eulerian phase, a dispersed Eulerian phase, or a dispersed Lagrangian phase.
In the dispersed phase limit, a hybrid EE-EL formulation is developed from first principles, which asymptotes to well-established EE and EL methods in limiting conditions. A smooth and dynamic transition criterion and a corresponding algorithm for conversion between EE and EL are developed. To use EE and EL in their respective regions of effectiveness (dense and dilute, respectively), the transition criterion is designed as a function of the local volume fraction and the local kinetic energy of random uncorrelated motion of particles. Simulations of particle evolution in turbulence, particle dispersion in sector blast, and reactive spray jet show the method’s validity and practical relevance.
In the resolved multiphase limit, the formulation limits to a compressible seven-equation diffused interface method (DIM). Novel extensions are developed for modeling surface tension, viscous effects, arbitrary EOS, multi-species, and reactions. The use of a discrete equations method (DEM) relieves the need to use conventional stiff relaxation solvers. Shock propagation through a material interface, surface tension-driven oscillating droplet, droplet acceleration in a viscous medium, and shock/detonation interaction with a deforming droplet are simulated to validate various part of the computational framework and demonstrate its applicability.
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Date Issued
2022-03-14
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Text
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Dissertation