  Reactive flows inside porous media play an important role in a number of
geophysical and industrial processes. Here we present three-dimensional
experimental measurements on how precipitation and flow patterns change with
the flow rate inside a model porous medium consisting of monodisperse glass
beads. The sample is initially filled with an aqueous solution of sodium
carbonate into which a solution of barium chloride is injected at a constant
flow rate. Upon contact and reaction, the two reactants produce water-insoluble
barium carbonate which precipitates onto the glass beads. This precipitate then
modifies the flow morphology which in turn changes the spatial distribution of
the precipitate. We discuss the influence of the flow rate on the morphology of
the flow pattern and demonstrate that neither viscous fingering nor the
Rayleigh-Taylor instability have any significant influence in our model system.
