Pattern of confined chemical garden controlled by injection speed

TL;DR

This study investigates how the pattern of confined chemical gardens formed by injecting cobalt chloride into sodium silicate solutions depends on injection speed, revealing distinct patterns and underlying mechanisms through experimental and mathematical modeling.

Contribution

It introduces a controlled system to study pattern formation in chemical gardens and develops a mathematical model incorporating viscous effects and Laplace pressure.

Findings

Filament pattern frequency increases with injection speed.

Injection pressure spikes when filament patterns form.

The mathematical model accurately predicts filament dynamics.

Abstract

Pattern of confined chemical garden was controlled by the speed of injected fluid, and their mechanism is discussed. A confined chemical garden system was constructed where an aqueous solution of cobalt chloride was injected into a cell filled with sodium silicate solution. The reaction of these two solutions resulted in the formation of precipitation. The viscosities of the prepared aqueous solutions were set to be similar in order to rule out the possibility of Saffman-Taylor instability. The injection front showed three distinctive patterns: algaes, shells, and filaments, which were dependent on injection speed. The injection pressure and the spatio-temporal pattern of the injected fluid were measured, and a significant increase in the injection pressure was observed when the filament pattern appeared, which indicated the existence of thin lubrication layer between the precipitation and the substrate. The filament pattern was further analyzed quantitatively, and the number of active filaments was determined to be proportional to the injection speed. A mathematical model was constructed that considered both the viscous effect from the thin luburiation layer and the Laplace pressure. This model successfully reproduced the characteristic filament dynamics.