ANOMALOUS-DISPERSION IN A DIPOLE FLOW GEOMETRY

The dispersion of a passive tracer in fluid flowing between a source a nd a sink in a Hele-Shaw geometry, characteristic of field scale flows in a layer or fracture, is considered. A combination of analytic and numerical techniques and complementary experimental measurements are e mployed, leading to a consistent picture. This dispersion process is f ound to be characterized by a power-law decay in time of the tracer co ncentration, with an exponential cutoff at very long times, in strong contrast to the Gaussian behavior associated with the widely used quas i-one-dimensional (1-D) models.