HR: 15:10h
AN: H13K-06    [Abstracts]
TI: Heat transport near sediment-water interfaces with bedforms
AU: * Cardenas, M B
EM: cardenas@nmt.edu
AF: Earth and Environmental Science New Mexico Institute of Mining and Technology, 801 Leroy Place, Socorro, NM 87801 United States
AU: Wilson, J L
EM: jwilson@nmt.edu
AF: Earth and Environmental Science New Mexico Institute of Mining and Technology, 801 Leroy Place, Socorro, NM 87801 United States
AB: The mechanical and thermal energy balance of streams, underlying sediments, and adjacent aquifers controls the distribution of lotic organisms. Thus, the energy transport within and between these systems is an issue of utmost importance in terms of understanding their ecology and biogeochemistry. In fast-flow systems, heat advection is equally important as, or more important than, heat conduction. In recent years, heat has been used as a tracer for fluid flow in deep aquifers as well as shallow unconsolidated fluvial deposits. However, recent studies have not addressed how fluid exchange across sediment-water interfaces (SWIs), driven by current-bedform interactions, affects thermal energy transport within the sediments. Moreover, even less is known regarding similar systems subjected to ambient groundwater discharge at a different temperature, e.g., gaining streams. We will present results of multiphysics numerical modeling along SWIs. Turbulent flow within the overlying water column (e.g., a river) is represented by the k-ω closure scheme for the Reynolds-averaged Navier-Stokes equations. Porous media flow within the sediments is governed by the groundwater flow equation. The water column and sediment flow problems are sequentially coupled, with the turbulent water column flow determining the pressure boundary along the SWI. Heat transport within the sediments is governed by the advection-dispersion equation while the flow field is determined a priori by the porous flow problem. Temperature effects on fluid properties are ignored. We do not model heat transport within the water column and instead consider the SWI as a constant-temperature boundary (i.e., the river is well-mixed) for the porous media domain. The numerical modeling is implemented using FEMLAB and CFD-ACE+. Cases with and without ambient groundwater discharge will be presented. Our results have implications not only on lotic ecology but also on the interpretation of past heat tracing experiments and the design of future heat tracer studies.
DE: 1814 Energy budgets
DE: 1829 Groundwater hydrology
DE: 1830 Groundwater/surface water interaction
DE: 1860 Streamflow
DE: 1878 Water/energy interactions (0495)
SC: Hydrology [H]
MN: Fall Meeting 2005