Tracer dispersion in rough channels: A two‐dimensional numerical study

KOPLIK, J.; IPPOLITO, I.; HULIN, J. P.

Physics of Fluids A: Fluid Dynamics

AIP

Año: 1993 vol. 5 p. 1333 - 1343

0899-8213

Numerical results are presented on the hydrodynamic dispersion of passive tracer in flow through a two‐dimensional channel bounded by parallel plates, one having substantial rugosities perpendicular to the flow. The simulation is based on the numerical solution of the microscopic Stokes and convention‐diffusion equations, over a range of Péclet numbers and of degrees of rugosity of the channel. One observes a tenfold increase of the effective dispersion between the smooth plate case (classical Taylor dispersion) and the maximum rugosity case, attributable to the trapping of tracer inside deep rugosities. The results are analyzed in terms of tracer exchange models, involving a characteristic exchange time between the low‐ and high‐velocity zones and their relative volume fractions, as a function of the Péclet number and the relative depth of the rugosities. The simulations are compared to ??echo?? dispersion experiments in which the tracer is first injected into the model and then, upon reversal of the fluid flow, drawn back through the inlet.