Very large eddy simulation of the Red Sea overflow

Mehmet Ilicak*, Tamay M. Özgökmen, Hartmut Peters, Helmut Z. Baumert, Mohamed Iskandarani

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

19 Citations (Scopus)

Abstract

Mixing between overflows and ambient water masses is a critical problem of deep-water mass formation in the downwelling branch of the meridional overturning circulation of the ocean. Modeling approaches that have been tested so far rely either on algebraic parameterizations in hydrostatic ocean circulation models, or on large eddy simulations that resolve most of the mixing using nonhydrostatic models. In this study, we examine the performance of a set of turbulence closures, that have not been tested in comparison to observational data for overflows before. We employ the so-called very large eddy simulation (VLES) technique, which allows the use of k s(-) ε models in nonhydrostatic models. This is done by applying a dynamic spatial filtering to the k s(-) ε equations. To our knowledge, this is the first time that the VLES approach is adopted for an ocean modeling problem. The performance of k s(-) ε and VLES models are evaluated by conducting numerical simulations of the Red Sea overflow and comparing them to observations from the Red Sea Outflow Experiment (REDSOX). The computations are constrained to one of the main channels transporting the overflow, which is narrow enough to permit the use of a two-dimensional (and nonhydrostatic) model. A large set of experiments are conducted using different closure models, Reynolds numbers and spatial resolutions. It is found that, when no turbulence closure is used, the basic structure of the overflow, consisting of a well-mixed bottom layer (BL) and entraining interfacial layer (IL), cannot be reproduced. The k s(-) ε model leads to unrealistic thicknesses for both BL and IL, while VLES results in the most realistic reproduction of the REDSOX observations.

Original languageEnglish
Pages (from-to)183-206
Number of pages24
JournalOcean Modelling
Volume20
Issue number2
DOIs
Publication statusPublished - 2008
Externally publishedYes

Funding

We are grateful for the support of National Science Foundation via grants OCE 0352047 and OCE 0620661. We thank Yeon Chang for providing the bottom topography, and Marcello G. Magaldi for his constructive criticism.

FundersFunder number
National Science FoundationOCE 0352047, OCE 0620661

    Keywords

    • Entrainment
    • k s(-) ε turbulence model
    • Red Sea overflow
    • Very large eddy simulation

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