Relating Representative Elementary Volume of Tortuosity to That of Porosity as Revealed from Computed Tomography Images

Abstract

Tortuosity and porosity are significant micro-scale parameters that have a major impact on many environmental processes and engineering applications that are usually implemented at a macroscopic scale. Thus, it is essential to quantify the corresponding representative elementary volume of these micro-scale properties to study and improve the understanding of different environmental applications, such as flow and transport of contaminates in porous media systems. 3D x-ray microtomography images of sand systems that have different sizes and geometry were used to compute two important microscopic properties such as porosity and tortuosity. Corresponding representative elementary volumes (REV) of these systems were computed by developing an efficient algorithm using Matlab. Representative elementary volume (REV) of tortuosity was related to that of porosity for each system, to determine whether an REV for porosity is sufficient to define REV for tortuosity. Findings revealed that for regular particles geometry REVmin of porosity was less than REVmin of tortuosity. However, for irregular particles geometry, the REVmin of porosity and REVmin of tortuosity were similar. This indicates that REVmin value of porosity depends on the geometry and the structure of the porous media. Whereas, REVmin value of tortuosity is not affected by the geometry. In addition, the number of particles required to reach REV region was found to be an easier method to be reflected upon.