Turbulent porous media flows are encountered in man-made systems such as catalytic bed reactors and advanced heat exchangers. Dispersion experienced by a scalar in these flows play an essential role in the overall efficiency and performance of these systems. In an effort to understand turbulent flows in such complex geometry, time resolved PIV measurements in a refractive index matched porous bed were made. Pore Reynolds numbers, Repore, based on hydraulic diameter, DH, and pore average velocity, Vint, were varied from 839–3964. Pore scale structures such as high momentum jet-like regions and recirculation regions are documented to exist within individual pores. The existence and distribution of these structures is found to vary from pore to pore. The heterogeneity in transport properties introduced due to these structures can be accounted for in estimating transport properties using the method of volume averaging. Eddy viscosity maps and mean velocity field maps, both obtained from PIV measurements, along with the method of volume averaging were used to predict the asymptotic longitudinal dispersion coefficient versus Reynolds number. Asymptotic values of longitudinal dispersion compare well to existing correlations. The role of molecular diffusion was explored by varying the Schmidt number in volume averaged governing equations for tracer transport and it was found that the dispersion coefficient was dictated by the interaction of wandering tracer with recirculation regions.

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