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Title: Horizontal and low-inclination oil-water flow investigations using laser-based diagnostic techniques
Author: Ibarra-Hernandez, Roberto
ISNI:       0000 0004 6422 9082
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2017
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The extraction of detailed phase and velocity-fields structures, which have not been fully explored in the literature, represents key information that can assist with the fundamental understanding of multiphase flows and be used to improve, develop, or validate closure relationships. This work is focused on the investigation of co-current oil-water flows in horizontal and low-inclination pipes in terms of flow regimes, in situ phase fractions, pressure gradients, and interface and flow velocity information. This was achieved by the implementation of shadowgraphy and laser-based techniques, along with pressure drop measurements. The laser-based experimental methodologies consist of a novel two-line light sheet arrangement which allows the extraction of simultaneous two-dimensional spatio-temporally resolved fluid-phase and velocity information in stratified flows for fluids with different refractive indices whose physical properties correspond directly to real field-industrial applications. Analysis of the experimental data reveals interesting flow structures and interactions between the fluids. The distribution of the phases is dependent on the flow velocities, the inclination of the pipe, and the design of the inlet section. The latter was found to have a significant effect on the flow instabilities either by generating droplets or promoting separation which in turn affects the pressure gradient along the pipe. Instantaneous velocity fields, mean velocity profiles, turbulence characteristics, and interface profiles are extracted from the laser-based measurements. Mean axial velocity profiles show characteristics of laminar and turbulent flows while wall-normal velocity profiles suggests that secondary flows (structures or vortices in the azimuthal direction), which are attributed to have an influence on the unsteadiness in the flow, are present in the investigated flows as single- or counter-rotating vortices generating a region of high shear where the vortices interact. Moreover, Reynolds stresses and mixing lengths profiles are constructed in order to offer further information on the level of turbulence in the flow. Experiments in upward pipe inclinations reveal that instabilities at the interfacial region are enhanced as a result of complex flow structures (e.g. large vortices and regions with only wall-normal velocity component). Mean and fluctuating velocity profiles, along with Reynolds stresses, at a given flow condition are strongly dependent on the pipe inclination for low mixture velocities; however, weakly dependent as the mixture velocity increases. In general, space- and time-resolve phase and velocity information has been obtained for stratified oil-water flows revealing detailed and complex interfacial and flow structures on both liquid phases.
Supervisor: Matar, Omar K. ; Markides, Christos N. Sponsor: Imperial College London
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral