HR: 1340h
AN: H23D-1615    [Abstracts]
TI: Solute Mixing in Thermally Induced Buoyancy Flow
AU: Yang, L
EM: li.yang@iws.uni-stuttgart.de
AF: Universitaet Stuttgart, Institut fuer Wasserbau, Pfaffenwaldring 61, Stuttgart, 70569, Germany
AU: Neuweiler, I
EM: insa.neuweiler@iws.uni-stuttgart.de
AF: Universitaet Stuttgart, Institut fuer Wasserbau, Pfaffenwaldring 61, Stuttgart, 70569, Germany
AU: Faerber, A
EM: arne.faerber@iws.uni-stuttgart.de
AF: Universitaet Stuttgart, Institut fuer Wasserbau, Pfaffenwaldring 61, Stuttgart, 70569, Germany
AU: * Cirpka, O A
EM: Olaf.Cirpka@eawag.ch
AF: Swiss Federal Institute of Aquatic Science and Technology (Eawag), Ueberlandstr. 133, Duebendorf, 8600, Switzerland
AB: Lack of transverse mixing has been identified as a key factor limiting natural attenuation of continuously emitted contaminants, because transverse mixing controls reactions between the contaminants in the plumes and oxidants in the ambient groundwater. Since most plumes are rather flat, vertical mixing is particularly important. However, under normal groundwater flow conditions, vertical mixing is slow, even in heterogeneous media under transient flow conditions. We suggest enhancing vertical mixing by inducing buoyancy flow applying local injection of heat. This leads to fingers and rotational flow, increasing the contact surface between the plumes and the surrounding groundwater and thus increasing mixing. Several experiments were carried out in an insulated two-dimensional sandbox with a Pyrex glass front pane. The box was homogeneously filled with glass beads. All experiments were performed under water-saturated conditions. Two lines of a blue tracer dye were injected as the initial concentration. Electrical heaters were installed inside the sandbox as the heat sources. We tested two operation modes of the sandbox, one with horizontal and the other with vertical heating. Pictures in both the visible and infrared spectra were taken to measure the concentration and temperature distributions. Concentrations were computed by post-processing of the pictures taken in the visible spectrum, whereas the temperature distribution was obtained from the infrared pictures. The initial results showed that the heating created buoyant fingers and rotational flow, resulting in stronger dilution of the tracer. Simulations of the experiments using a modified version of SUTRA (USGS) agreed reasonably with the experimental data.
DE: 1832 Groundwater transport
SC: Hydrology [H]
MN: 2007 Fall Meeting