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unpleasant inconvenience.
We present a set of complementary experimental and numerical tools for studying
miscible fluid displacements in porous media with large scale heterogeneities.
Experiments are realized in transparent 2D Hele-Shaw cells allowing optical
observations and in 3D packings of glass beads with an acoustical technique for
imaging fluid displacements. Permeability heterogeneities are modeled by spatial
variations of either the local aperture of the Hele-Shaw cell or the diameter of the
grains used in the packing. The Hele-Shaw cell model provides high resolution maps of
the invasion front location at regular time intervals and of the flow lines: the
velocity field is determined by combining these informations. Acoustical images of
relative concentration distributions in the 3D packing are in agreement with Hele-Shaw
cell data and can be obtained in a broader range of experimental situations. Such
experiments realized with a stabilizing density contrast between invading and displaced
fluids demonstrate a strong reduction of the front width at low flow velocities, a
similar reduction is obtained at high velocities with a stabilizing viscosity
contrast. The technique is also applicable to study fluid displacements in natural
opaque media. Numerical simulations by a Boltzmann lattice technique using a
Stokes-like diffusive term to smooth out the effect of permeability discontinuities
provide complementary informations. They are shown to give similar results as
experiments for same flow parameter values and to allow for a fast exploration of a
broad range of fluid properties and flow situations.