Effect of grid size on diffusion in heterogeneous media

[Won Woo Yoon]

Hello all,

I am currently seeking advice regarding a phenomenon I observed while testing various grid sizes for a diffusion problem in a heterogeneous domain.

The system is divided into a source zone, where uraninite dissolves and releases species, and a bentonite zone, where diffusion takes place.

I observed that using a finer grid size results in a progressively larger amount of uranium being released from the source into the bentonite.

Comparing the results of the attached input files (test_hr_1D_diss.in vs. test_lr_1D_diss.in), the Total UO2++ concentration remains identical within the source zone, while the concentration in bentonite zone is higher in the finer grid case.

This phenomenon occurs when the release from the source is driven by mineral dissolution. In the cases where I assigned a high initial uranium concentration to the source without mineral dissolution (test_hr_1D_const.in and test_lr_1D_const.in), the Total UO2++ profiles were identical across all domains regardless of grid size.

I have attached the input files and the database used.

I would appreciate any advice or suggestions on how to resolve this grid dependency issue.

Best regards,

Won Woo Yoon