Mixing of solutes in heterogeneous porous media under thermally induced buoyancy-flow conditions

• Applicant: Professor Dr.-Ing. Rainer Helmig, since 3/2008
• Subject Area: Hydrogeology, Hydrology, Limnology, Urban Water Management, Water Chemistry, Integrated Water Resources Management
• Term: from 2004 to 2010
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 5424303

The lack of transverse solute mixing has been identified as a key factor limiting natural attenuation of contaminant plumes in aquifers 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 wide than thick. Under standard groundwater flow conditions, unfortunately, the parameters describing vertical dispersive mixing are fairly small, even in heterogeneous media under transient flow conditions. We propose to deliberately induce unstable flow conditions by local heat injection in order to overcome insufficient vertical mixing in groundwater. The creation of buoyant fingers and rotational flow increases the surface area of the solute plume and thus enhances mixing with the surrounding groundwater. We want to study the effects of thermal convection on solute mixing by controlled experiments in sandboxes. We will vary the type of fillings, boundary conditions and operation modes. We will measure concentration and temperature distributions by optical methods in the visual and infrared spectrum and compare them to numerical simulations. The present application is restricted to free thermal convection facilitating a quasi two-dimensional set up. The second phase of the project will also include situations with ambient flow (mixed convection).

• DFG Programme: Research Grants
• Ehemalige Antragstellerinnen / Ehemalige Antragsteller: Professor Dr.-Ing. Olaf A. Cirpka, until 8/2007; Dr.-Ing. Arne Michael Färber, from 8/2007 until 8/2007; Professorin Dr. Insa Neuweiler, from 8/2007 until 3/2008