Journal of Porous Media

ON THE PREDICTIONOFAN AVERAGE DROPLET SIZE EVOLUTION DURING TRANSPORT IN HOMOGENEOUSPOROUS MEDIA UNDERLAMINAR FLOW CONDITIONS

ABSTRACT

This paper deals with the prediction of a spatially averaged droplet size during transport within homogeneous porous media. More precisely, this transport process occurs in a mixture of a continuous aqueous phase which includes a discontinuous one in the form of droplets. The mixture flows in a homogeneous porous medium under laminar flow conditions. The collection of γ-order moments, Sγ, is used here to describe the time evolution of the spatially averaged mean diameter of spherical droplets, mainly because Sγ satisfies the convective/diffusive transient transport equation. As it is well known, breakup and coalescence are the primary local phenomena controlling the size of droplets in such a process. The essence of the so-called "Sγ concept" is that break-up and coalescence processes determine the source terms in a transport equation for the moments of an averaged characteristic size, representative for the droplet size. The velocity vector at any point is calculated by typical computational fluid dynamics simulations. The assumptions made are that (a) the flow conditions correspond to low Reynolds numbers, (b) the local flow field is independent of the droplets and thus, the droplet size is small enough compared with the mean pore diameter, and (c) the liquid/solid interfaces are chemically neutral. Since the proposed constitutive model adequately simulates the droplet transport process, it is used here for the investigation of the effect of porous geometry and flow characteristics on the droplet size.