Experimental and Simulation Study on Validating a Numerical Model for CO2 Density-Driven Dissolution in Water

Abstract

Carbon dioxide density-driven dissolution in a water-filled laboratory flume of the dimensions 60 cm length, 40 cm height, 1 cm thickness, was visualized using a pH-sensitive color indicator. We focus on atmospheric pressure conditions, like in caves where CO 2 concentrations are typically higher. Varying concentrations of carbon dioxide were applied as boundary conditions at the top of the experimental setup, leading to the onset of convective fingering at differing times. The data were used to validate a numerical model implemented in the numerical simulator DuMu x . The model solves the Navier-Stokes equations for density-induced water flow with concentration-dependent fluid density and a transport equation, including advective and diffusive processes for the carbon dioxide dissolved in water. The model was run in 2D, 3D, and pseudo-3D on two different grids. Without any calibration or fitting of parameters, the results of the comparison between experiment and simulation show satisfactory agreement with respect to the onset time of convective fingering, and the number and the dynamics of the fingers. Grid refinement matters, in particular, in the uppermost part where fingers develop. The 2D simulations consistently overestimated the fingering dynamics. This successful validation of the model is the prerequisite for employing it in situations with background flow and for a future study of karstification mechanisms related to CO 2 -induced fingering in caves.

On the Role of Density‐Driven Dissolution of CO2 in Phreatic Karst Systems

“…Hence, the model solved in 2D can be viewed as a pseudo-3D approach. Class et al (2020) showed that this approach was able to reproduce experimental results in stagnant water satisfactorily.…”

“…While the study of Michel-Meyer et al (2020) refers to processes in porous media, we remind that our focus here is primarily on open water bodies, where we have no such experimental data available. The modeling study presented below builds on a small experimental laboratory setup, previously used by Class et al (2020) under stagnant conditions for validating the numerical Navier-Stokes model which is briefly explained in Appendix A.…”

A Dynamic and Fully Implicit Non‐Isothermal, Two‐Phase, Two‐Component Pore‐Network Model Coupled to Single‐Phase Free Flow for the Pore‐Scale Description of Evaporation Processes

“…We chose the latter here. This approach has been applied successfully for a number of different applications with thin, slit‐like domains (Venturoli & Boek, 2006; Laleian et al., 2015; Kunz et al., 2015; Class et al., 2020). The channel is discretized with 30 cells in vertical and 133 cells in horizontal direction such that three grid cells coincide with one pore body at the interface.…”

Dynamics of CO2 Density‐Driven Flow in Carbonate Aquifers: Effects of Dispersion and Geochemistry

“…This instability promotes CO 2 mixing due to convection, which is beneficial for the whole process. Beside CS, convective mixing is relevant to a wide range of other natural and industrial applications, such as enhanced oil recovery (EOR) (Kahrobaei et al, 2012;Sabet et al, 2018;Sheng, 2011), thermal and compositional mixing in the sea and oceanic water and karstification (Anderson et al, 1979;Ronen et al, 1988;Smith, 2004;Class et al, 2020), industrial chemical production (Wylock et al, 2014(Wylock et al, , 2017 and enhanced heat transfer using nanofluids (Heris et al, 2007;Li et al, 2003).…”