Miscible displacements with a chemical reaction in a capillary tube

Miscible displacement of a more-viscous liquid by a less-viscous one with a chemical reaction in a capillary tube was investigated experimentally and theoretically. In such a flow field, the less-viscous liquid continuously leaks from the tip of the fingershaped boundary between the two liquids to form another thin finger depending on flow condition. This is called a "spike." Experimental results show that in the spike product is clearly or scarcely observed when the initial reactant concentration in the less-viscous liquid is sufficiently larger or smaller than the stoichiometry, respectively. On the basis of theoretical results, a model is proposed in which the difference in the reaction plane's location in either the less-viscous liquid or in the boundary (determined by the variation in the initial reactant concentrations) results in a significant difference between the locations of the boundary and the reaction plane, this difference being affected by the spike configuration of the boundary.