Studying Effect of Travel Distance on Dispersion Coefficient in Layered Soil Perpendicular to Flow Direction using Numerical Model

One of the most important measurable properties of the porous medium is dispersivity, which is used in advection-dispersion equations related to pollutant transport in the study of groundwater. In the past, the dispersivity coefficient for the entire porous medium was considered as a constant coefficient, but many studies conducted in the last few decades have shown that the dispersivity depends on many parameters, including the travel distance. Since most of these studies have been conducted in homogeneous porous media, in this research, the effect of travel distance of ۲۰, ۵۰ and ۸۰ cm on the dispersivity coefficient in a porous medium corresponding to coarse, medium and fine granularity was investigated. The results obtained in this research showed that in all travel distances, the volume of pore water reached one before reaching the relative concentration of ۰.۵, and the pollutant travel rate decreased with increasing travel distance, which was consistent with the results of other studies. Also, the numerical modeling by Hydrus numerical model showed that this model was able to calculate the value of the diffusion coefficient for the travel distances of ۲۰, ۵۰ and ۸۰ cm with the RMSE error equal to ۰.۰۶۵, ۰.۰۶۸ and ۰.۰۶۱, respectively, which indicates its high accuracy is in simulating and moving the contaminant in the porous medium.

Keywords:

Diffusivity , Transfer Distance , Layered Porous Medium , Brigham Model , Hydrous