An Experimental Investigation of the Effect of Idealized Heterogeneity on the Dispersion of Miscible Fluids

Laboratory experiments on dispersion of miscible fluids in a porous medium have been performed. Dimensionally scaled two‐dimensional models were packed with both homogeneous and idealized heterogeneous permeability distributions. Longitudinal dispersion coefficients were calculated by mapping the flow into the streamline‐equipotential coordinate system. The results of these experiments indicate that the dispersion coefficient is not a function of the spatial scale of the system provided that the permeability distribution is preserved as the system dimension is increased. Also, it was found that an inclusion of permeability differing from the surrounding medium could result in both Gaussian and non‐Gaussian tracer distributions depending upon the location of the inclusion, and systems with heterogeneous permeability distributions sometimes resulted in dispersion similar to that for homogeneous media. In some instances, the dispersion everywhere within the system appeared to be Fickian, but when the dispersion was monitored at the withdrawal point from the system, the dispersion appeared to be non‐Fickian.