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Institut für Wasser- und Umweltsystemmodellierung - IWS

Abstract

 
   

"Horizontal Redistribution of Two Fluid Phases in a Porous Medium - Experimental and Numerical Investigations"

In this thesis an experimental setup was developed to derive experimental data for the horizontal redistribution of air and water in order to investigate driving forces for flow and testing the validity of the extended Darcy´s Law. The experiment was set up as proposed by Philip (1991): A horizontal flume preserving a saturation discontinuity was carried out. The discontinuity was realized by a thin metal sheet, dividing the flume into two sections. Those carried sands with different initial water saturations. By removing the metal sheet, the redistribution process is started while saturation and wetting phase/non-wetting phase pressures are measured at various points along the flume. For measuring the saturation a gamma-source detector unit is used, for measuring pressures transducers sensible for water and air are used. The experiments show a persisting saturation discontinuity at the wetting-draining interface of the flume even after 30 days, where nearly no flow occurred. And still gradients of pressure and saturation existed on each side of the discontinuity. Applying the extended Darcy´s Law on the redistribution problem, pressure is the only driving force causing flow in the flume, since gravity is neglected because of the minor height of the flume, But in fact, gradients in both pressure and saturation are still observable when nearly no flow occurred, indicating the validity of an alternative approach for modelling two-phase flow by Hassanizadeh and Gray (1990, 1993a,b). Their approach is based on rational thermodynamics and leads to more driving forces capable to balance existing pressure gradients in equilibrium states.