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Buoyancy- and chemically-driven pattern formation in the contact zone between two fluids
To characterize phenomena occuring in the contact zone between two fluids, it is possible to place them between two plates separated by a small gap, thus confining the flows in a quasi 2D geometry. We will here present two studies performed in this type of set up, called Hele-Shaw cell.
In a first part, we will focus on a buoyancy-driven instability developing at the miscible interface between two liquids. In the case of a viscous and dense fluid injected into a less viscous and less dense fluid, we report the observation of a thin stripes oriented in the direction of the flow. The onset time of the instability and the wavelength of the pattern are characterized as a function of the flow rate, the thickness of the cell and the relative properties of the two fluids.
In a second part, we will show that a coupling between hydrodynamics and a precipitation chemical reaction is able to produce a large variety of patterns when the concentrations of the two reagents are changed.