This work concerns the numerical simulation of boiling on unstructured grids.
PhD thesis under the supervision of:
Abstract
The objective of this thesis is the numerical simulation of the boiling phenomenon on unstructured grids. Boiling is the phase change of fluid particles from the liquid phase to the vapor phase under the action of thermal fluxes at the interface separating the two phases. Boiling is thus encountered in two-phase flows and driven by the mass transfer rate at the interface. This mass transfer rate is computed from the thermal fluxes on both sides of the interface. Consequently, a highly accurate numerical method is needed to locate the interface throughout the simulation. The Navier-Stokes equations are then coupled to the heat equation by means of the mass transfer rate at the interface. Such simulations have been performed by Tanguy et al. (J. Comput. Phys., 2014) on two-dimensional axisymmetric cartesian grids. In this thesis, we extend this methodology to three-dimensional unstructured grids (composed of irregular tetrahedra, useful to describe complex geometries). We then developed a specific solver in the YALES2 code (finite-volume-based code for simulations of two-phase flows on 3D unstructured grids). The interface motion is captured by the Level Set method. Phase change implies velocity and pressure discontinuities at the interface which especially depend on the mass transfer rate. These discontinuities are taken into account by the Ghost Fluid Method, with two velocity fields and two temperature fields. This methodology being already well established for structured cartesian grids, the contribution of this thesis relies on the ability to simulate phase change by boiling on three-dimensional unstructured grids. The particularities of unstructured grids have demanded numerous developments for the reinitialization of the Level Set function after advection, as well as the use of high-order operators for the computation of the mass transfer rate at the interface. The proposed developments
are finally validated on unstructured grids against the analytical test-case of a 3D bubble expanding inside a superheated quiescent liquid.
Jury’s members:
M. Sébastien TANGUY, Maître de Conférences, Université Paul Sabatier (Toulouse), Rapporteur
M. Olivier DESJARDINS, Associate Professor, Cornell University (Ithaca, NY), Rapporteur
M. Julien REVEILLON, Professeur des Universités, Université de Rouen, Examinateur
M. François-Xavier DEMOULIN, Professeur des Universités, Université de Rouen, Examinateur
M. Emmanuel MAITRE, Professeur des Universités, Grenoble INP, Examinateur
M. Philippe MARTY, Professeur Emérite, Université Grenoble Alpes, Examinateur, Directeur de thèse
M. Guillaume BALARAC, Maître de Conférences, Grenoble INP, Membre invité
M. Giovanni GHIGLIOTTI, Maître de Conférences, Université Grenoble Alpes, Membre invité
M. Vincent MOUREAU, Chargé de Recherche, Université de Rouen, Membre invité