Phase Field Theory on ANSYS fluent: Implementation of Spinodal Decomposition of Binary Mixture

Abstract

Diffuse interface model(also known as phase field theory) is a powerful tool which can lead to a complete description of many phenomena like demixing of partial miscible liquids, droplets breaking out and whenever the interface dimension is system one alike. In the present thesis this theory is applied to the specific study of liquid mixtures which present a temperature and composition dependent lack of miscibility, so that a deep quench or concentration shift is enough to trigger phase separation of the initial system. This feature can be exploited in many extraction processes, even ones which employ thermolabile liquids. Therefore, the implementation of the phase field model on a commercial simulation software seems to be a useful tool which would allow us to investigate the aforementioned systems. This thesis work is divided into different parts; at first the underlying theory will be presented, this outline ranges from statistical thermodynamics to incompressible binary mixture equation of motion, therefore the adopted numerical scheme will be described, together with the aspects related to the implementation of the mathematical expressions into the solver. In the end, the results of simulations about a square box will be presented, though some kind of changes about the boundary conditions will be made. Subsequently the results of analogue system in more complex geometries. The study of the spinodal decomposition is a topic largely covered in scientific literature albeit differently; a lot of work has been done to correctly implement it using different methods. Particular attention requires [1] ,where the spinodal decomposition is simulated using a semi implicit time scheme and a spectral one for the spatial discretization. Despite the goodness of the paper there is a CFL constrain that is avoided in fluent given the implicit nature of the solver. Others like [2] obtained good results(the data herein obtained are benchmarked with theirs) but used pseudo-spectral techniques that are difficult to adapt in complex geometries; so this work opens up many possibilities because it employs much more powerful techniques