Heidelberg 2006 – wissenschaftliches Programm

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UP: Umweltphysik

UP 3: Boden- und Agrarphysik

UP 3.2: Fachvortrag

Montag, 13. März 2006, 14:45–15:00, E

Unstable Gravity Water Fingering in Homogeneous Unsaturated Porous Media — •Fereidoun Rezanezhad, Nadiya Smolyar, Hans-Jörg Vogel, and Kurt Roth — Institute of Environmental Physics, University of Heidelberg, Germany

Gravity-driven flow fingers during infiltration through unsaturated porous media are studied, experimentally. We use a Hele-Shaw cell (160×60×0.3 cm) with a shallow fine-textured layer on top of a homogenous coarse-textured layer. An infiltrating water front becomes unstable upon transition into the coarse layer and breaks up into so-called flow fingers. Fingered flow is visualized by light transmission and is recorded with a digital camera. The resulting time series of images is analyzed to obtain a high-resolution representation of the dynamics of water content. The Light Transmission Method (LTM) was calibrated by comparison with simultaneous measurements of X-Ray absorption which showed very close agreement between these two techniques. This research aims to develop a light transmission method that allows visualization of the unstable fingered flow phenomena in transient flow fields and investigate the multiphase and transport process in unsaturated porous media. The vertical redistribution and dynamics of longitudinal and transverse water saturation profile was determined to study the saturation profile inside fingers, width, velocity and number of fingers for different flow rates conditions. To improve the understanding of the related processes, we added a dye tracer to visualize the velocity field and separation of a mobile and an immobile component of water within flow fingers.