Mixing in a Moderately Sheared Salt-Fingering Layer Public Deposited

http://ir.library.oregonstate.edu/concern/defaults/p8418p81h

Descriptions

Attribute NameValues
Creator
Abstract or Summary
  • Mixing due to sheared salt fingers is studied by means of direct numerical simulations (DNS) of a double-diffusively unstable shear layer. The focus is on the “moderate shear” case, where shear is strong enough to produce Kelvin–Helmholtz (KH) instability but not strong enough to produce the subharmonic pairing instability. This flow supports both KH and salt-sheet instabilities, and the objective is to see how the two mechanisms work together to flux heat, salt, and momentum across the layer. For observed values of the bulk Richardson number Ri and the density ratio R[subscript]ρ, the linear growth rates of KH and salt-sheet instabilities are similar. These mechanisms, as well as their associated secondary instabilities, lead the flow to a fully turbulent state. Depending on the values of Ri and R[subscript]ρ, the resulting turbulence may be driven mainly by shear or mainly by salt fingering. Turbulent mixing causes the profiles of temperature, salinity, and velocity to spread; however, in salt-sheet-dominated cases, the net density (or buoyancy) layer thins over time. This could be a factor in the maintenance of the staircase and is also an argument in favor of an eventual role for Holmboe instability. Fluxes are scaled using both laboratory scalings for a thin layer and an effective diffusivity. Fluxes are generally stronger in salt-sheet-dominated cases. Shear instability disrupts salt-sheet fluxes while adding little flux of its own. Shear therefore reduces mixing, despite providing an additional energy source. The dissipation ratio Γ is near 0.2 for shear-dominated cases but is much larger when salt sheets are dominant, supporting the use of Γ in the diagnosis of observed mixing phenomena. The profiler approximation Γ[subscript]z, however, appears significantly overestimate the true dissipation ratio.
Resource Type
DOI
Date Available
Date Issued
Citation
Series
Keyword
Rights Statement
Funding Statement (additional comments about funding)
Publisher
Language
Replaces
Additional Information
  • description.provenance : Submitted by Deborah Campbell (deborah.campbell@oregonstate.edu) on 2012-05-16T18:02:00Z No. of bitstreams: 1 SmythWDCEOASMixingModeratelySheared.pdf: 3360929 bytes, checksum: 2db1a6978f7f94ad160936123c63fa38 (MD5)
  • description.provenance : Made available in DSpace on 2012-05-16T18:02:00Z (GMT). No. of bitstreams: 1 SmythWDCEOASMixingModeratelySheared.pdf: 3360929 bytes, checksum: 2db1a6978f7f94ad160936123c63fa38 (MD5) Previous issue date: 2011-07

Relationships

Parents:

This work has no parents.

Last modified

Downloadable Content

Download PDF

Items