Mixing of solutes in heterogeneous porous media under thermally induced buoyancey-flow conditions
In the subsurface, the lack of transverse solute mixing has been identified as a key factor limiting natural attentuation of contaminant plumes originating from permanently emitting contaminant sources. Vertical mixing between the contaminants in the plume and dissolved oxidants in the ambient groundwater is most decisive since many plumes are rather flat than thick. Under normal groundwater flow conditions, the parameters decsribing vertical dispersive mixing are fairly small, even in heterogeneous media under transient flow conditions.
In this project, the unstable flow conditions will be deliberately induced by local heat injection to overcome the insufficient vertical mixing in groundwater. The creation of buoyant fingers and rotational flow increases the surface area of the plumes thus enhances mixing with the surrounding groundwater. During the course of the project, the effects of thermal convection on solute mixng will be studied by controlled experiments in sand boxes. Variable types of fillings, boundary conditons and operation modes will be investigeted. Concentration and temperature distributions will be measured by optical methods in both visible and infrared sprectrum and compared with numerical simulations.
Deutsche Forschungsgemeinschaft (DFG)