CHARACTERIZATION OF AXI-SYMMETRICAL FLOW IN THE VADOSE ZONE

Abstract eng:
Dye tracer and visualization techniques have been widely used for describing water flow patterns in soils and particularly, for determining the volumetric water content in one dimensional and two dimensional laboratory experiments. The present study describes a three dimensional laboratory experiment (axi-symmetrical condition) using color image analysis for determining the spatial distribution of the water content. The infiltration of a dye (fluorescein) mixed with water is achieved under axi-symmetrical condition in a Plexiglas chamber filled with an initially wet sand. Both infiltration and drainage processes are visualized under blue light filter and recorded on videotape. The image analysis technique used for determining the saturation state is based on the use of a limited color palette which allows us to quantify the evolution of the saturation state in the sand. Simultaneously, nine tensiometers connected to a data acquisition system, are used to determine the negative water pressure in the sand. The measurements of the suction confirm the existence of a second wetting front (after the dye solution flow) due to the initial mobile water content in the sand.

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