A NEW APPROACH FOR ESTIMATING MACRODISPERSIVITY USING DYE TRACER AND SPATIAL MOMENT ANALYSIS

Abstract

Laboratory dye tracer experiments with a pulse source were conducted in homogeneous and stratified porous formations under saturated unidirectional flow conditions. A new methodology using spatial moment analysis linked with image processing of a dye tracer behavior was developed to estimate macrodispersivities both in longitudinal and lateral directions. A calibration relation between the dye concentration and the corresponding pixel brightness was established to quantify the spatial distribution of dye tracer. Both dispersivities asymptotically approached a certain value and exhibited a dependency on the difference of hydraulic conductivities associated with the stratification, which played a significant role in the evolution of transverse dispersion. Laboratory study was extended by a random walk particle tracking approach to reconstruct the estimated dispersivity transition, demonstrating a good agreement between the experimental and numerical results not only in homogeneous but in stratified porous media of concern.