Modeling and numerical simulation of transient flows in superposed porous and pure-fluid layers

摘要

In this work we are concerned with the modeling and numerical simulation of transient flows in superposed porous and pure-fluid layers, with heat transfer and chemical reactions. In the first part, we propose a single-domain approach, thermal non-equilibrium model which incorporates porosity as a field variable. The advantage of this approach is that it does not require additional matching conditions at the interface. Also, the flow structures at the transition layer between the two regions are resolved, which renders this model ideal for the study of unsteady flows. In the second part, we describe the proposed numerical algorithm for the treatment of the governing equations. It is a generalization of projection methods for the Navier-Stokes equations to multi-phase flows, which is straight-forward to implement in a computer code. In the third part, we present our work on constant-density shear flows at the interface between a porous medium and a pure fluid. The discussion includes both analytical results, in the form of a linear stability analysis, and results from numerical simulations of both 2D and 3D shear layers. In the fourth part we study fluid flow with heat transfer in the domains of interest. In particular, we are concerned with the problems of natural and forced convection in a channel, as well as shear layers under thermal stratification. Finally, in the fifth part, we focus on results from our simulations of reacting flows through a porous medium. In the first case considered, the ignition of the porous fuel is induced by exposure to a stream of hot oxidizer. In the secondcase, the porous fuel is ignited by spark.