Análise da dispersão de poluentes no solo usando fluidodinâmica computacional

Abstract

The transport of pollutants through porous media is a major problem and causes significant concern worldwide. In this scenario, it becomes essential to evaluate the transport mechanisms of pollutants through porous media, in order to estimate their final dispersion. This work focused on carrying out a laboratory-scale sandbox experiment, where the migration of a dye marker in a saturated porous medium was examined through digital image analysis. A numerical simulation was carried out using Computational Fluid Dynamics (CFD) and the experimental results were compared with the numerical simulation. The finite volume technique was used in a structured three-dimensional mesh, laminar regime, isotropic medium, saturated soil, and multiphase flow. The results demonstrated a favorable alignment between numerical and experimental results. Once validated, the method was used to evaluate the dispersion of pollutants in the soil from a possible leak from a generic stabilization pond. Two types of geometry were used, a single layer and a multilayer model. With the single-layer geometry, simulations were carried out with different flow speeds, volumetric fraction of pollutants, porosity, and soil permeability. The concentration of the pollutant increases as flow velocities increase, however, the time required to reach the highest pollutant value decreases, indicating that the degree of pollution of the porous medium was greater. By decreasing porosity and permeability, there was a decrease in the time needed to reach the highest value of the pollutant, however, there was no reduction in concentration. When porosity increases and permeability decreases, the time to reach the highest pollutant value at all points analyzed was longer, however, the concentration did not show a significant difference in both cases. The results of the multilayer model showed that when using a soil with low porosity and permeability in the surface layer, there is less water retention, facilitating its transmission to the lower layers of the soil. When comparing the single-layer model with the multilayer model, it was found that the depth reached by the plume was lower in the multilayer model, however, there was no significant decrease in the volumetric fraction values of pollutants in the soil layers.