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Title: Lattice Boltzmann modelling of immiscible two-phase flows
Author: Zhang, Duo
Awarding Body: University of Liverpool
Current Institution: University of Liverpool
Date of Award: 2015
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The scope of the current thesis is the comprehensive understanding of the droplet impact and spreading dynamics on flat and curved surfaces with the aim of simulating high density ratio immiscible two phase flows in porous media. Understanding the dynamic behavior of droplet impingement onto solid substrate can provide significant information about the fluid flow dynamics in porous structures. The numerically study process will be realized by using a high density ratio multi-phase lattice Boltzmann model which is able to simulate multi-phase flows in complex systems. The interfacial information between the two immiscible phases can be captured without tracking or constructing the vapour-liquid interface. A three dimensional lattice Boltzmann model is applied on the study of the impaction of a liquid droplet on a dry flat surface for a liquid-gas system with large density ratio. The impaction of liquid droplet on a curved surface for the liquid-gas system with large density ratio and low kinematic viscosity of the fluid is computed by a two-dimensional multi-relaxation-time (MRT) interaction-potential-based lattice Boltzmann model based on the improved forcing scheme. The dynamics behaviors of the spreading of the liquid droplet on the flat surface as well as the impaction of the liquid droplet on a curved surface are computed, followed by their dependence on the Reynolds number, Weber number, Galilei number and surface characteristics. Moreover, an improved force scheme is proposed for the three-dimensional MRT pseudopotential lattice Boltzmann model which is based on the improved force scheme for the Single relaxation time (SRT) pseudopotential lattice Boltzmann model and the Chapman-Enskog analysis. The validation for the new developed three-dimensional multi-relaxation time lattice Boltzmann model is carried out through Laplace’s law ad by achieving thermodynamic consistency. In addition, the relationship between the fluid-solid interaction potential parameter Gw and the contact angle is investigated for the new developed three-dimensional MRT lattice Boltzmann model. The immiscible two-phase flow in porous media is carried out by a two dimensional MRT lattice Boltzmann model. The porous media structures with different geometrical properties are artificially generated by a Boolean model based on a random distribution of overlapping ellipses/circles. Furthermore, the impact of geometrical properties on the immiscible two-phase flows in porous media is investigated in the pore scale. The lattice Boltzmann model results provide significant information i on the interface between the two immiscible phases in complex systems, it is easy to apply for complex domains with bounce back boundary wall condition and be able to handle multi-phase and multi-component flows without tracing the interfaces between different phases.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available