Magnetic resonance imaging of reaction-driven viscous fingering in a packed bed

The formation of 3-dimensional viscous fingers has been investigated in a packed bed using magnetic resonance imaging. Fingering patterns are produced as a result of the formation of a highly viscous wormlike micelle solution formed at the interface between solutions of cetyltrimethylammonium bromide (CTAB) and sodium salicylate (NaSal), which have similar viscosities, but that are significantly lower to the wormlike micelle solution. In this system, fingers are driven by an interfacial instability, rather than a Saffman-Taylor instability. The structure of the fingering patterns, which were found to be sensitive to flow rate, where analysed using histogram plots characterizing the distribution of pores containing the CTAB solution. This system shares similar characteristics to the growth of biofilms.