Prediction of Finger Spacing for NAPLs Infiltrated in Porous Media
Four typical NAPLs were selected for vertical infiltration experiments conducted in two-dimensional visible sandbox apparatus.Totally 75 images were captured by the digital camera to have the front infiltration morphological information.Fractal dimension was used to estimate the effective interfacial tension for finger spacing prediction.In addition,finger spacing predicted by the means of capillary pressure head was compared with the predictions by fractal dimension.The results showed that predictions by the capillary pressure head method deviated more from the observed finger spacing,with the absolute error values varied between 1%-93% while the prediction errors by fractal dimension were between 2%-25%.NAPLs denser than water have quite high prediction errors calculated by the capillary pressure head method.The predicted finger spacing showed a significant linear correlation with those observed in practice.Compared with the capillary pressure head method,the fractal dimension method predicted more precisely especially for DNAPLs,which could be used for unstable finger flow prediction in the contaminated soil risk management and in the effective design of recovery and remediation schemes.