Interface Fingering Instability Triggered by a Density-Coupled Oscillatory Chemical Reaction via Precipitation

A density fingering
hydrodynamic instability is triggered by a
chemical reaction at the interface between two fluids. The density
instability is controlled by the density gradient between both solutions,
while the excitability of the bubble-free Belousov–Zhabotinsky-1,4-cyclohexanedione
(BZ-CHD) oscillatory chemical reaction controls the importance of
the chemistry in the system. Both parameters are thoroughly analyzed,
and the mechanism underlying the instability is unveiled. The experimental
observations lead us to modify the existing and accepted models for
the BZ-CHD reaction within this context. The important role played
by precipitation is considered in this context and included into the
model. The modified kinetic model once coupled with fluid dynamics
along with the precipitation mechanism was able to reproduce the experimental
observations.