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Title: A combined immersed boundary/phase-field method for simulating two-phase pipe flows
Author: Argyropoulos, Christos
ISNI:       0000 0004 6423 1449
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2015
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The investigation of the flow in a pipe is a major issue for the pipeline capacity but also plays an important role for the control and prevention of phenomena that could damage the pipe, such as corrosion, erosion, and the potential formation of wax or their deposits. Therefore, the characterization of the flow patterns is also a major issue for the prediction of the distribution over the cross-section of the pipe, in order to understand any problems that may interrupt or shut down the operation of the production line. The main purpose of the present effort is to develop an appropriate numerical method for simulating two-phase pipe flows. Advanced Computational Fluid Dynamics (CFD) methods are employed as Navier-Stokes solver, while a Phase-Field method is used to simulate the interfacial region between the two fluids. A Ghost-Cell Immersed Boundary Method (GCIBM) was developed and implemented for the reconstruction of smooth rigid boundaries (pipe wall) based on the work of Tseng and Ferziger (2003). The method was also modified in order to incorporate appropriate boundary conditions for coupling the Phase-Field and Navier-Stokes solvers for two-phase pipe flows. Tseng and Ferziger (2003) used the GCIBM for turbulent single-phase flows; the present modified version comprises a continuation of the method for handling two-phase pipe flows. The computational model is capable of handling large density and viscosity ratios with good accuracy. The developed GCIBM algorithm was validated against analytical solutions for single and two-phase pipe flow, presenting very good agreement. The computational model was compared to available experimental data from the literature for single rising bubbles and bubble coalescence in vertical pipe also with good agreement. The numerical method was used to investigate the lateral wall effects of a 3-D single bubble in a viscous liquid for different pipe diameters and bubble flow regimes. The dynamics of 3-D Taylor bubbles was also examined in vertical pipes for different properties of fluids (e.g. air-water system) and dimensionless parameters relevant to the problem (e.g. ReB, Eo, Mo). The numerical results were compared with available experimental and numerical data from the literature, presenting good agreement.
Supervisor: Boek, Edo Sponsor: Engineering and Physical Sciences Research Council
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral