In this dissertation, advances are made in understanding both the way hyporheic exchange impacts riverbed morphodynamics and the physical processes that lead to turbulent momentum transfer in the first few grains of riverbed sediments. In terms of physical advances in understanding the interplay between bedform movement and hyporheic exchange, we have identified two long-term bedform morphodynamic behaviors – the locked and segregated states. These cases have numerous implications for river functioning and are expected to decrease sediment transport rates and nutrient transfer to subsurface microbial communities while increasing the long-term storage of both nutrients and contaminants. In terms of analyzing turbulent momentum transfer, the extent of the transition region, where turbulent flow in the freestream decays to Darcy flow deeper in the bed, and the vortical structures that lead to the sweeping and injection of turbulent momentum were identified. In terms of analyzing the transfer of solutes from the freestream into the porewater, a set of useful tools have been introduced. Double averaging of the LES equations (DA-LES) allows for integration over depth and heterogeneities to generate profiles of the Reynolds’ stress, drag forces, and the velocity. Lagrangian particle tracking has been used to find the autocorrelation time and turbulent diffusion coefficient, allowing for the direct parameterization of an upscaled model of solute transport.

Creator

• Dallmann, Jonathan

DOI

• https://doi.org/10.21985/n2-tvkn-3m51

Subject

• Environmental engineering
• Mechanical engineering
• Civil engineering

Language

• en

Alternate Identifier

• etdadmin_upload_819194
• http://dissertations.umi.com/northwestern:15572

Keyword

• Hyporheic Exchange
• LES
• Flume Experiments
• Turbulence
• Bedforms

Date created

• 2021-01-01

Resource type

• Dissertation

Rights statement

• In Copyright