| Abstrakt: |
Constrictions in the void space between soil particles govern hydraulic conductivity, internal stability, and filtration performance of sands and gravels. Various analytical, numerical, and image-based methods have been proposed to measure void constrictions based solely on analysis of particle and void geometry. These geometric constrictions are increasingly being used in models to predict hydraulic conductivity or filtration performance. However, both of these phenomena depend not only on the void geometry, but also on the directions and magnitudes of fluid velocities within the void space. This paper presents computational fluid dynamics (CFD) simulations performed on microcomputed tomography (microCT) images of voids in real sands, as well as idealized materials generated by discrete element modeling (DEM). Laminar flow conditions are considered and an alternative definition of a void constriction is presented, the hydraulic constriction, which is based on fluid velocities rather than void geometry. The data show that for laminar flow, where Darcy's law is applicable, the position, size, and orientation of hydraulic and geometric constrictions share many similarities, but there are measurable differences, which should be considered in hydraulic conductivity and filtration analyses. [ABSTRACT FROM AUTHOR] |
