Effect of Pore‐Wall Roughness and Péclet Number on Conservative Solute Transport in Saturated Porous Media

Abstract

AbstractWhile modeling solute transport has been an active subject of research in the past few decades, the influence of pore‐wall roughness on contaminant migration has not yet been addressed. We therefore conduct particle tracking simulations in three porous domains that have different pore‐wall roughness characteristics. Specifically, we consider five surface fractal dimensions ds = 1.0, 1.1, 1.2, 1.4, and 1.6, and four different Péclet numbers Pe = 10, 102, 103, and 105. Overall, arrival time distributions are simulated for 60 scenarios (3 domains  5 surface fractal dimensions  4 Péclet numbers) some of which show heavy‐tailed patterns indicating non‐Fickian transport. To interpret the simulations and quantify the transport behavior, we analyze the resulting arrival time distributions by the continuous time random walk (CTRW) approach. Results show that, on average, as the surface fractal dimension increases from 1.0 to 1.6, the CTRW model parameters , an exponent showing the degree of anomalous transport, v, the average solute velocity, and t2, the cut‐off time to Fickian transport, remain nearly constant. However, the dispersion coefficient, D, increases and the characteristic transition time, t1, decreases. We found t1 and D are more sensitive to pore‐wall roughness compared to the other CTRW parameters. We also found that as the Péclet number increases from 10 to 105, on average, v and D increase, t1 and decrease, and t2 remains nearly constant. The simulations demonstrate that the exponent and the dispersion coefficient are correlated to the average solute velocity.