Smart Fluids in Hydrology: Use of Non-Newtonian Fluids for Pore Structure Characterization

Monday, 14 December 2015
Poster Hall (Moscone South)
Majdi R Abou Najm1, Nabil M Atallah2, John S Selker3, Clément Roques4, Ryan D. Stewart5, David E Rupp6, George Saad2 and Mutasem El-Fadel7, (1)American University of Beirut, Beirut, 1107, Lebanon, (2)American University of Beirut, Beirut, Lebanon, (3)Oregon State University, Biological and Ecological Engineering, Corvallis, OR, United States, (4)University of Rennes, Rennes Cedex, France, (5)Virginia Polytechnic Institute and State University, Blacksburg, VA, United States, (6)Oregon State University, Corvallis, OR, United States, (7)Department of Civil and Environmental Engineering, American University of Beirut, Beirut, Lebanon
Classic porous media characterization relies on typical infiltration experiments with Newtonian fluids (i.e., water) to estimate hydraulic conductivity. However, such experiments are generally not able to discern important characteristics such as pore size distribution or pore structure. We show that introducing non-Newtonian fluids provides additional unique flow signatures that can be used for improved pore structure characterization while still representing the functional hydraulic behavior of real porous media. We present a new method for experimentally estimating the pore structure of porous media using a combination of Newtonian and non-Newtonian fluids. The proposed method transforms results of N infiltration experiments using water and N-1 non-Newtonian solutions into a system of equations that yields N representative radii (Ri) and their corresponding percent contribution to flow (wi). This method allows for estimating the soil retention curve using only saturated experiments. Experimental and numerical validation comparing the functional flow behavior of different soils to their modeled flow with N representative radii revealed the ability of the proposed method to represent the water retention and infiltration behavior of real soils. The experimental results showed the ability of such fluids to outsmart Newtonian fluids and infer pore size distribution and unsaturated behavior using simple saturated experiments. Specifically, we demonstrate using synthetic porous media that the use of different non-Newtonian fluids enables the definition of the radii and corresponding percent contribution to flow of multiple representative pores, thus improving the ability of pore-scale models to mimic the functional behavior of real porous media in terms of flow and porosity. The results advance the knowledge towards conceptualizing the complexity of porous media and can potentially impact applications in fields like irrigation efficiencies, vadose zone hydrology, soil-root-plant continuum, carbon sequestration into geologic formations, soil remediation, petroleum reservoir engineering, oil exploration and groundwater modeling.