Experimental study of linear and nonlinear regimes of density-driven instabilities induced by CO2 dissolution in water

摘要

Density driven instabilities produced by CO_2 (gas) dissolution in water containing a color indicator were studied in a Hele Shaw cell. The images were analyzed and instability patterns were characterized by mixing zone temporal evolution, dispersion curves, and the growth rate for different CO_2 pressures and different color indicator concentrations. The results obtained from an exhaustive analysis of experimental data show that this system has a different behaviour in the linear regime of the instabilities (when the growth rate has a linear dependence with time), from the nonlinear regime at longer times. At short times using a color indicator to see the evolution of the pattern, the images show that the effects of both the color indicator and CO_2 pressure are of the same order of magnitude: The growth rates are similar and the wave numbers are in the same range (0–30 cm~(-1)) when the system is unstable. Although in the linear regime the dynamics is affected similarly by the presence of the indicator and CO_2 pressure, in the nonlinear regime, the influence of the latter is clearly more pronounced than the effects of the color indicator.