Dissolution at the pore scale


Figure 1: Dissolution of a circular gypsum chip: The initially circular chip (left panel) dissolves asymmetrically (center panel), because of the fluid flow (left to right). The simulated shape is shown in the right panel. The experiments were made by Filip Dutka and Piotr Szymczak.

Figure 2: Area of the gypsum chip as a function of time; experiment and simulation.

For a quantitative comparison between simulation and experiment, we have investigated the dissolution of a circular chip, 20 mm in diameter and 0.5mm thick, within the same microfluidic cell. In this case the there is no gap on top of the chip and the fluid flows around it. The initially circular chip (left panel) dissolved asymmetrically, because of the fluid flow (left to right). After 4 days the chip is adopting a petal shape, with a sharp tip pointing in the downstream direction (center). The simulation generates a similar shape (right).

The area of the dissolved chip can be extracted from the images and the results are plotted in Figure 2. The simulations include a correction to the diffusivity from the activity coefficients of the aqueous ions. This makes for a significant (25%) slowing down of the time scale by reducing the effective diffusion of the ions and brings the simulation results into better, but not yet perfect agreement with experiment. The discrepancies remain an active area of investigation.

Dissolution of a circular chip: Evolving shape and concentration field.

References

Collaborators

Vitaliy Starchenko
Piotr Szymczak




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Last updated August 2018