Natural stream systems contain a variety of flow geometries which contain flow
separation, turbulent shear layers, and recirculation zones. This work focuses on
streams with dead zones. Characterized by slower flow and recirculation, dead
zones are naturally occurring cutouts in stream banks. These dead zones play an
important role in stream nutrient retention and solute transport. Previous experimental work has focused on idealized dead zone geometries studied in laboratory
flumes. This work explores the capabilities of computational fluid dynamics (CFD)
to investigate the scaling relationships between flow parameters of idealized geometries and the time scales of transport. The stream geometry can be split into two
main regions, the main stream flow and the dead zone. Geometric parameters of
the dead zone as well as the bulk stream velocity were varied to determine a scaling relationship for the transport time scales. These flow geometries are simulated
using the RANS turbulence model with the standard k-ω closure. The standard
first order dead zone model is expanded to a two region model to accommodate the
multiple time scales observed in the simulation results. While this model currently
has limited predictive capability, it provides physical insight into the functional
dependence of the dead zone time scales. LES is used to evaluate the performance
of the Reynolds Averaged Navier-Stokes (RANS) turbulence model and to describe
the anisotropic turbulence characteristics. The differences between the time averaged flow field for Large Eddy Simulation (LES) and RANS was determined to
have a significant impact on passive scalar transport. / Graduation date: 2012
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/30147 |
| Date | 04 June 2012 |
| Creators | Drost, Kevin J. |
| Contributors | Apte, Sourabh, Haggerty, Roy |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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