Multiphase flow simulations benefit a variety of applications in science and engineering as forexample in the dynamics of bubble swarms in heat exchangers and chemical reactors or in theprediction of the effects of droplet or bubble impacts in the design of turbomachinery systems.Despite all the progress in the modern computational fluid dynamics (CFD), such simulations stillpresent formidable challenges both from numerical and computational cost point of view.Emerging as a powerful numerical technique in recent years, the lattice Boltzmann method(LBM) exhibits unique numerical and computational features in specific problems for its abilityto detect small scale transport phenomena, including those of interparticle forces in multiphaseand multicomponent flows, as well as its inherent advantage to deliver favourable computationalefficiencies on parallel processors.In this thesis two classes of LB methods for multiphase flow simulations are developed whichare coupled with the level set (LS) interface capturing technique. Both techniques are demonstratedto provide high resolution realizations of the interface at large density and viscosity differenceswithin relatively low computational demand and regularity restrictions compared to theconventional phase-field LB models. The first model represents a sharp interface one-fluid formulation,where the LB equation is assigned to solve for a single virtual fluid and the interfaceis captured through convection of an initially signed distance level set function governed by thelevel set equation (LSE). The second scheme proposes a diffuse pressure evolution descriptionof the LBE, solving for velocity and dynamic pressure only. In contrast to the common kineticbasedsolutions of the Cahn-Hilliard equations, the density is then solved via a mass conservingLS equation which benefits from a fast monolithic reinitialization.Rigorous comparisons against established numerical solutions of multiphase NS equations forrising bubble problems are carried out in two and three dimensions, which further provide anunprecedented basis to evaluate the effect of different numerical and implementation aspects ofthe schemes on the overall performance and accuracy. The simulations are eventually appliedto other physically interesting multiphase problems, featuring the flexibility and stability of thescheme under high Re numbers and very large deformations.On the computational side, an efficient implementation of the proposed schemes is presented inparticular for manycore general purpose graphical processing units (GPGPU). Various segmentsof the solution algorithm are then evaluated with respect to their corresponding computationalworkload and efficient implementation outlines are addressed.
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