Physically based model for extracting dual permeability parameters using non-Newtonian fluids.

Abstract

Dual-permeability models simulate flow and transport within soils characterized by preferential (macro) and matrix (micro) pore domains that each possess distinct hydraulic properties. The lack of suitable methods for determining appropriate and physically meaningful model parameters remains the major challenge to applying these models. Here, we present a method that constrains dual-permeability model parameters using experimental saturated flow results from water and a non-Newtonian fluid. We present two sub-models that solve for the effective pore sizes of micropores and macropores, with macropores represented either with cylindrical (for biological pores) or planar (for shrinkage cracks and fissures) pore geometries. The model determines as well the percent contribution (wi) of the representative macro and micro pores to water flow. We applied the model to experimental soil samples constructed with capillary tubes describing the macropores, and proved its ability to derive the bimodal pore size distributions in dual-domain soils using only two fluids. As such, we present this method of characterization of dual structures for improved modeling of non-uniform preferential flow and transport in macroporous soils.