Experimental study of CO2 convective dissolution: The effect of color indicators

Abstract

Color indicators are often used for visualization purposes in experimental studies of CO2 convective dissolution in aqueous solutions. We analyze and compare here experimentally the hydrodynamic fingering pattern induced by CO2 dissolution in aqueous solutions of various color indicators. Characteristics of the convective patterns are measured as a function of time to study whether the choice of the color indicator or its concentration has an influence on the dynamics. We also compare the visualization of the fingering instability with a color indicator to the pattern observed with a Schlieren technique tracking changes in index of refraction. We find that color indicators are able only to track pH isocurves and do not always allow to capture the full extent of the fingers. We conclude that color indicators should be used with caution in experimental works devoted to quantify properties of CO2 convective dissolution.