The effect of particle shape of porous media on the longitudinal dispersivity: contaminant transport

Subject Areas : Farm water management with the aim of improving irrigation management indicators

ghasem  mirzaei ¹ (MSc of Water Structure Engineering, Instructor, Meshgin Shahr Faculty of Agriculture, University of Mohaghegh ardabili, Ardabil, Iran)

Received: 2017-12-10 Accepted : 2018-03-04 Published : 2018-04-21

Keywords: particle shape, FEFLOW, Breakthrough Curve, CXTFIT, self-potential method,

Abstract :

One of the most challenging quantities in analyzing the transfer of contaminant in the porous medium is the determination of longitudinal dispersivity. In this research, the effects of the porous media particle shape on the longitudinal dispersivity were investigated by experiments on three column of soil (broken texture, river sand, spherical texture). Flow and contaminant (NaCl) were injected at five levels of velocities and the Breakthrough curve was extracted at five points along the column by Self-Potential Method, Then, by simulating the results with FEFLOW software and the inverse analysis with CXTFIT2 software, longitudinal dispersivity was determined. The results indicate that, for constant velocity, the medium with spherical texture has a longitudinal dispersivity greater than the other two medium and in the sandy medium it is more than the broken texture. This can be due to the increase in the contact surface as well as the path’s tortuosity, with the particle coming out of the spherical shape. With increasing velocity, the longitudinal dispersivity decreases in all three medium. Also, as the particles are closer to the spherical shape, the scale effect will be greater, and with increasing velocity, the decrease in the longitudinal dispersivity in these medium will be less.

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