Fig. 4

a Characteristic dimensionless velocity (relative to the mean velocity) profiles versus dimensionless distance from the center of the channel (relative to the channel half height) for the three regimes of flow. The viscous profile is parabolic (Poiseuille). The porous profile is flattened by the resistance to flow through the porous media. The unsteady profile exhibits a peak between the core and the boundary layer due to fluid inertia. b Characteristic dimensionless concentration profiles versus dimensionless distance from the center of the channel for the regimes of dispersion. The profiles mirror those of velocity, except for the no-flux boundary condition at the wall. In the legend, the flow regime is given before the slash and the dispersion regime after the slash. The unsteady curves are shown for Womersley number α² = 100, and the porous curves are shown for Darcy number Da² = 200