Theoretical basis for the measurement of local transverse dispersion in isotropic porous media

Spreading of a conservative solute in potential flow in a helical porous me dium is dominated by the radial velocity distribution within the domain. Hi gher velocities at the inside of the helix compared to the outside leads to spreading that is balanced by transverse pore-scale dispersion. The angula r moments of the concentration distribution exhibit the typical behavior of Taylor-Aris dispersion in which the rate of change of the second central m oment is inversely proportional to pore-scale transverse dispersion. We pre sent numerical results for the angular moments over the entire time range a nd derive analytical expressions for the angular macrodispersion coefficien t at the large time limit. We propose a method in which macrodispersion is measured in a helix filled with the porous material of interest in order to infer pore-scale transverse dispersivity values that are difficult to dete rmine with existing methods.