Simulação numérica fina do processo de transporte de interfaces

Abstract

In this work a new method for analysing problems related to two—phase flows, in the brands of Computational Fluid Mechanics, is presented. One of the great difficulties in the simulation of this class of flows is related to the presence of moving-boundaries. The technique employed here is called Front-Tracking Method. The present formulation allows the tracking and geometric definition of interfaces. lt allows also to place dinamically the moving-boundary and physical properties variation as well. Such results are possible through a so called Indicating function. A process for boundary grid regularization is also used, in order to warranty the numerical stability. Some preliminary results are showed, where the boundaries are tracked by a creeping flow field of tangent—inverse and parabolic types. A harder test consists in forcing a velocity ' shock in the flow field. Such a procedure permits testing the geometric parameters calculation, grid updating and the visualization of the indicating function. A passive bubble—tracking is simulated between two flat parallel plates, through the solution of the well-known Navier-Stokes equations. Two configurations are used: two fixed plates and a relative displacement between them. Finally, the results for active boundary- tracking are presented, via the solution of the Navier—Stokes equations, where the presence of interfacial stress changes the pressure and velocity fields of the continuous phase. Several values for Interfacial stress are used, and the resulting pressure and velocity fields are observed. The results for the pressure jump among the phases are compared to the analytical ones, for circular bubbles. The comparison allows a preliminary validation for the method and the computational code.