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 language | English (US) |
|---|---|
| Pages (from-to) | 183-206 |
| Number of pages | 24 |
| Journal | Ocean Modelling |
| Volume | 20 |
| Issue number | 2 |
| DOIs | |
| State | Published - 2008 |
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Keywords
- Entrainment
- k s(-) ε turbulence model
- Red Sea overflow
- Very large eddy simulation
ASJC Scopus subject areas
- Atmospheric Science
- Oceanography
- Geotechnical Engineering and Engineering Geology
- Computer Science (miscellaneous)
Cite this
Very large eddy simulation of the Red Sea overflow. / Ilicak, Mehmet; Ozgokmen, Tamay M; Peters, Hartmut; Baumert, Helmut Z.; Iskandarani, Mohamed.
In: Ocean Modelling, Vol. 20, No. 2, 2008, p. 183-206.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Very large eddy simulation of the Red Sea overflow
AU - Ilicak, Mehmet
AU - Ozgokmen, Tamay M
AU - Peters, Hartmut
AU - Baumert, Helmut Z.
AU - Iskandarani, Mohamed
PY - 2008
Y1 - 2008
N2 - 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.
AB - 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.
KW - Entrainment
KW - k s(-) ε turbulence model
KW - Red Sea overflow
KW - Very large eddy simulation
UR - http://www.scopus.com/inward/record.url?scp=36749007953&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=36749007953&partnerID=8YFLogxK
U2 - 10.1016/j.ocemod.2007.08.002
DO - 10.1016/j.ocemod.2007.08.002
M3 - Article
VL - 20
SP - 183
EP - 206
JO - Ocean Modelling
JF - Ocean Modelling
SN - 1463-5003
IS - 2
ER -