Browsing by Author "Jose, Surabhin Chackiath"

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Experimental investigations on longitudinal dispersive mixing in heterogeneous aquifers
(2005) Jose, Surabhin Chackiath; Helmig, Rainer (Prof. Dr.-Ing.)
Reactive mixing of compounds in porous media is a topic of current research interest because accurate estimation of reaction rates are crucial in planning aquifer remediation methods. It is suggested that relative parameters for dilution are better quantities to estimate reaction rates than the generally used classical macrodispersion coefficients. Most of the concepts developed in the field of reactive mixing are based on theoretical and numerical studies, and have not been experimentally tested. In this thesis, reactive mixing experiments are carried out in two different setups and the applicability of some of the existing numerical and theoretical studies to the observed data is tested. Two types of experimental setups - a homogeneously packed one-dimensional column setup and a heterogeneously packed two-dimensional sandbox setup - are used in the study. The column is 2m long with an inner diameter of 10cm, while the sandbox has dimensions 14m x 0.5m x 0.13m. Silica sand is used to fill both setups. The heterogeneity in the sandbox resembles the sedimentation pattern in nature. A conservative test and a reactive test each is conducted in both setups. Fluorescein is used as both the conservative and the reactive tracer. Dilution coefficients are estimated from the temporal moments of the conservative breakthrough curves obtained within in the porous media. Fiber optic fluorometry is used as the point measurement system. The measurement tip of the optic fiber probes has a diameter of 2.5mm. Reactive mixing in the porous media is predicted from the dilution coefficients estimated from the conservative tests, and is compared with the actual reactive mixing from the reactive tests. I conclude that point-like measurements provide reliable information of dilution and mixing in porous media, and therefore are effective enough in predicting product formation, provided sorption parameters are effectively quantified. I found that regions with large contrast in hydraulic conductivity give opportunity to enhanced mixing. Considering the typical length scales of the heterogeneities, the experimental findings are qualitatively in agreement with the linear stochastic theory.