Coherent Turbulent Structures in the Body of Pseudo-Steady Gravity Currents
Abstract
Owing to their ubiquitous nature, interest in the structure and dynamics of gravity currents is well established. The head has been extensively studied, and it's structure is well understood. Comparatively little work has been conducted looking at the structure of the body, despite this often forming the majority of the flow. Similarly, the flow is typically assumed to be two-dimensional. A combination of three-dimensional DNS and planar PIV has been used to investigate the body of pseudo-steady gravity currents, and more particularly the impact of Reynolds and Schmidt numbers on the formation of coherent turbulent structures. These structures are of interest due to their ability to transport mass, momentum and temperature, as well as their potential impact on erosion and deposition in sediment laden flows. PIV was used to investigate a range of Reynolds numbers by considering various slopes with a constant influx, as well as a constant slope with varying influx. DNS, carried out using the spectral element code Nek5000, was used to investigate a range of Schmidt numbers, as well as a potentially wider range of Reynolds numbers than experimentally achievable, with a constant influx and varying slope. Multiple vortex identification techniques were compared to identify the number and size of structures within the flow. The impact of these structures on the dynamics was then established. It was found that increasing the Reynolds number results in a greater number of smaller vortices, while increasing Schmidt number suppresses the formation of structures and reduces the thickness of the mixed layer. This work aims to describe the turbulent structure of the body of pseudo-steady gravity current flow for the first time, and identify how this structure is affected by both Reynolds and Schmidt numbers. Additionally we aim to identify when assuming a Schmidt number of 1, as seen frequently in the literature, is reasonable. This research is advancing understanding of mixing processes within gravity currents.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMOS13C1487M
- Keywords:
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- 1824 Geomorphology: general;
- HYDROLOGYDE: 3002 Continental shelf and slope processes;
- MARINE GEOLOGY AND GEOPHYSICSDE: 3022 Marine sediments: processes and transport;
- MARINE GEOLOGY AND GEOPHYSICSDE: 3045 Seafloor morphology;
- geology;
- and geophysics;
- MARINE GEOLOGY AND GEOPHYSICS