Modelagem matemática de escoamentos bifásicos usando a metodologia IMERSPEC combinada com os métodos VOF e Front- Tracking

Abstract

The present work proposes to extend the IMERSPEC methodology to solve two-phase flows. This methodology based on the coupling of Fourier psedospectral method (FPSM) and immersed boundary method (IBM). The main features of the FPSM are the high rate of numerical convergence, high numerical accuracy combined with high computational efficiency because it uses the Fast Fourier Transform algorithm, and beside that, in order to solve the Navier-Stokes equations, solving linear system for pressure-velocity coupling is not necessary. To deal with two-phase flows with moving and deformable geometry, two methods were coupled the IMERSPEC methodology: the Front-Tracking method (FT) and Volume of Fluid method (VOF). The FT method works with two domains, the Eulerian, where the equations for the fluid are evaluated and the Lagrangian for modeling the interfaces. In the FT, both domains are coupled by using interpolation and distribution process, with no restriction on the movement and deformation of the dispersed phase of the Lagrangian mesh over Eulerian domain. The disadvantages of the FT method are a possible mass loss and the need of a fragmentation and coalescence bubble model. The VOF method defines the surface by the volume fractions which allows the fragmentation and coalescence of bubbles without the requirement of implementing a specific model, however it may present numerical instabilities. The results obtained by evaluating the spurious currents, mass conservation and analysis through numerical experimentation of bubbles rise show that IMERSPEC-FT can be considered validated and promising, while the IMERSPEC-VOF presents promising results for cylindrical bubble regime.