Density difference driven instabilities in porous media

In the present work, we analyze density driven instabilities in miscible fluids in a random packing of monosized glass spheres (porous medium). The aim of this work is to detect heterogeneities in flow velocity using tracer dispersion because of the sensitivity of this technique. The influence of non-Newtonian rheological properties on the displacement front between two fluids of different densities is particularly studied. We compared the width of the displaced fronts in the case of Newtonian fluids with the same density contrast. Our analysis allows us to find a characteristic gravity number G (ratio between hydrostatic and viscous pressure gradients). A same threshold value of G for Newtonian and non Newtonian solutions is directly related to the structural properties of the porous medium. Received: 30 March 2000