Simulation of fluid flow and permeability in cohesionless soils

This paper reports on a new laboratory methodology for the determination of the structure of pores, a method for the analysis of the data to obtain th e statistics of the pore structure distribution, simulation of porous media with statistics consistent with those in the specimens, numerical simulati on of fluid flow in images of porous media, and the determination of permea bilities from the numerical experiments and comparison with the results of laboratory experiments. The computed flow fields show that flow in porous m edia is restricted to preferential paths depending on the size and connecti vity of pores. Whole areas of the pore structure are relatively isolated fr om the flow because of bottlenecks. The distribution of the isolated region s depends on the angularity of the grains and the porosity of the medium. T he more angular the grains are the greater is the possibility for the prese nce of isolated regions. For grains with the same angularity a decrease in the porosity leads to concentration of flow along preferential flow paths. The permeability tensor coefficients are derived from the flow fields of th e two-dimensional images as well as the three-dimensional computer-simulate d images of soil microstructure. The numerical values of permeability and p ermeability anisotropy ratio compare well with laboratory experimental data .