Numerical modeling of multi-phase flows and bubble dynamics

The development of computational fluid dynamics (CFD) tools allows engineering to analyze the behavior of fluid systems. In the framework of the SoFiA project, supported by the European Union, numerical simulations of the motion of soap bubbles are in focus. The following thesis explores the possibilities to simulate the dynamic movement, with particular regards to the analysis of the collision between soap bubbles. The developed code relies on Basilisk, an open-source software that allows to work with two-phase systems, providing simplicity in modeling different types of physics. After the verification of the program against benchmarks tests, the focus of this work is on two test cases: the contact of a soap bubble with an hydrophobic surface, and the collision between soap bubbles. Because of the limited literature on the numerical treatment for these cases, some modeling hypotheses have been explored in relation to the thickness of the bubbles and the dynamic role of the surfactants. First, an increased thickness has been adopted, which allows to reduce the overall computational expense and may be justified using self-similarity concepts. Second, a viscoelastic model (Oldroyd-B) is explored to model the constributions of micelles in the soap films. Towards a rational organization of the results, the dimensionless numbers characterizing the problem have been analyzed to understand the different physical effects in the two test cases. From the results obtained, it is possible to observe that surface tension plays an important role on the dynamics, and significantly affects the contact behavior of soap bubbles with solid walls and other bubbles.