Experimental Study of Fingering Flow in Porous Hele-Shaw Cells

Due to different types of geological media in the unsaturated zone (ranging from homogeneous sand to heterogeneous fractured media.), it is generally accepted that water and solutes may flow through the unsaturated zones via preferential paths until they reach groundwater. Preferential flow in the vadose zone is the focusing of flow into narrow channels. The flow through preferential paths is extremely important in agriculture, in the hydrological processes of infiltration and in the transport of agrochemicals through the soil profile. The important aspect of preferential flow is that water, as well as pollutants dissolved in it, can infiltrate downward through such pathways much faster than predicted by homogeneous flow with plane wetting fronts. The term preferential flow refers to several phenomena which have in common the non-uniform and often rapid movement of water through soils which does not tend to move as a horizontal wetting front. Fingering (flow instability) is oneform of preferential flow resulting from instability of infiltration through the unsaturated coarse soil. This book describes the physical process concerning the unstable fingering flow in porous media.