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Ph.D. Thesis Proposal
By
Achyut Panchal
(Advisor: Prof. Suresh Menon)
02:30 PM, Thursday, 9 November, 2017
Montgomery Knight Building, Room 317
MODELING & SIMULATION OF DENSE-TO-DILUTE MULTIPHASE REACTING FLOWS
Abstract: Predicting performance of liquid fueled combustors using large-eddy simulations (LES) require accurate modeling of the spray characteristics of the fuel injector, but most existing models are often limited to the dilute regime where droplets are treated as Lagrangian point particles within a Eulerian gas phase model far from the actual injector. The near-field of the injector for these methods is often modeled using empirical breakup models (still within the EL method) that require tuning to match the experimental data, or by using decoupled interface resolved primary breakup simulations of the liquid jet from the injector which are too numerical intensive for their use in the far-field. A fully coupled approach should take advantage of both these near and far field techniques, but is currently not possible as the intermediate regimes where the finite volume fraction and finite size particle effects play an important role have not been fully addressed, and are one of the primary focus of this effort. For LES, point particles are much smaller than the grid resolution, and so, subgrid modeling is also required for their coupling with the unresolved gas phase.
In this study, the relatively unexplored moderately dense regime and its transition to dilute regime is investigated using a mathematically consistent procedure that combines a Eulerian-Eulerian (EE) dense model with a dense-to-dilute Eulerian-Lagrangian (EL) and a finite-size particle method. Hybrid EE-EL dispersed phase method that transitions from pure EE regime in the dense phase to EL in the dilute regime is developed allowing for a finite fraction of the cell volume to be occupied by the droplets. In addition, a finite-size particle method is proposed to allow the droplets to be larger than the grid without resolving the interfacial boundary layers. Coupling of this method with the hybrid EE-EL approach is also considered using representative configurations. This hybrid method is especially needed in the near injector region where the grid is refined to resolved the gas flow but can be so small as to violate the point-particle assumption. Subgrid dispersion and vaporization modeling for unresolved gas-spray coupling in LES is combined with the EE-EL hybrid method to establish a method that can capture many of the near-injector physical processes. Verification and validation (V & V) are conducted using canonical problems involving dispersion and vaporization of single/multiple droplets in laminar/turbulent environment followed by more complex flows such as reacting spray jets.
Committee Members:
Prof. Suresh Menon (Advisor)
Prof. Joseph Oefelein
Prof. Timothy Lieuwen
