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Large-eddy simulations of multi-phase plumes in crossflow and stratified flow

Mitrou, Elli 2020. Large-eddy simulations of multi-phase plumes in crossflow and stratified flow. PhD Thesis, Cardiff University.
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Abstract

The mixing and transport properties of bubble plumes make them an interesting and unique component of environmental and engineering applications, such as destratification and aeration of lakes or reservoirs, prediction of gas release from accidental well blow-outs or from natural vents, chemical and/or nuclear reactors. Understanding the hydrodynamics of the interaction between the gas and liquid phases is essential to predict more accurately their movement and therefore to achieve more efficient results in the aforementioned applications. The description of multi-phase flows has been a challenging task for both Computational Fluid Dynamics modellers and experimentalists, due to the different treatment of the carrier and dispersed phases. Experimental studies have provided valuable information mainly about the bubbles' characteristics, whilst numerical methods arise as a tool to be used for more detailed study not only of the dispersed phase, but also for the surrounding continuous phase. In this thesis, a high-fidelity large-eddy simulation computational approach is adopted, including a Eulerian-Lagrangian method for the description of the dispersed phase. The combination of these numerical methods others balance between computational resources and accuracy. The numerical approach is applied and validated with simulations of multi-phase plumes in cross flow and stratified ambient flow. A detailed investigation of the flow mechanisms and the interaction of liquid-gas phases are visualized through 2D and 3D streamlines, isosurfaces of and velocity contours. The numerical results have been thoroughly validated against experimental studies. This study is among the first to attempt the case of bubble plume in cross flow numerically with a 3D code. And most likely the first one to employ an E-L arrangement, which is, given the limitations of interface tracking methods, among the most accurate applicable to this case. The results are reliable (given by the validation) and the insights provided (such as the Reynold stresses and the turbulent structures) cannot be predicted by other models.

Item Type: Thesis (PhD)
Date Type: Completion
Status: Unpublished
Schools: Engineering
Uncontrolled Keywords: multi-phase flows, bubbles, crossflow, LES
Date of First Compliant Deposit: 24 May 2021
Last Modified: 24 May 2021 14:56
URI: http://orca.cardiff.ac.uk/id/eprint/141525

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