Méthode réglée de niveau pour le cheminement d'interface : développement et applications

Abstract

Numerical simulation for multiphase flows requires a specific approach to describe interface behaviours, such droplet coalescence or break-up. Front tracking methods are based on the Lagrangian tracking of marker particles; they are more efficient when the interface curvature does not exhibit stiff behaviours, However it appears that topological changes, which are involved in droplet coalescence, depend on an interaction time parameter of great influence. Volume of Fluid method is describing the volumetric fraction of each phase in grid cells. The main disadvantage of the method is the interface reconstruction that appears quite difficult on 2D domain, and numerically prohibitive on 3D domain. A consequence is the uncertainty on interface curvature and thus on surface tension forces. Our work deals with a Level Set method that describes the interface with the zero level curve of a continuous function. This function is defined as the signed distance to the interface. Its advancement is updated with a convection equation, coupled with a constraint that ensures that the function is always a signed distance. Different numerical methods can be implemented to take into account for surface tension forces (delta formulation or ghost fluid method), which depend on the curvature of zero level curve, in Navier Stokes equations. We provide the advantages and the drawbacks of this method and we discuss about its potential improvements. The main target of this study is to reach a better understanding of primary and secondary atomization, processes, studying jet stability and droplets collisions.