Computational Fluid Dynamics Modelling of a Midlatitude Small Scale upper Ocean Front
A numerical model is implemented to describe fluid dynamic processes associated with mid-latitude small- scale (10 km) upper ocean fronts by using modified state of the art computational fluid dynamics tools. A periodic system was simulated using three different turbulent closures: 1) URANS-Reynol...
| Main Authors: | , |
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| Format: | Article |
| Language: | English |
| Published: |
Isfahan University of Technology
2016-01-01
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| Series: | Journal of Applied Fluid Mechanics |
| Subjects: | |
| Online Access: | http://jafmonline.net/JournalArchive/download?file_ID=40250&issue_ID=235 |
| _version_ | 1818229475584770048 |
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| author | Pablo Cornejo Hector H Sepúlveda |
| author_facet | Pablo Cornejo Hector H Sepúlveda |
| author_sort | Pablo Cornejo |
| collection | DOAJ |
| description | A numerical model is implemented to describe fluid dynamic processes associated with mid-latitude small-
scale (10 km) upper ocean fronts by using modified state of the art computational fluid dynamics tools. A
periodic system was simulated using three different turbulent closures: 1) URANS-Reynolds Stress Model
(RSM, seven equation turbulence model), 2) LES-Standard Smagorinsky (SS, algebraic model), and 3)
LES-Modified Smagorinsky, introducing a correction for non-isotropic grids (MS). The results show the
front developing instabilities and generating submesoscale structures after four days of simulation. A
strongly unstable shear flow is found to be confined within the mixed layer with a high Rossby number
(Ro > 1) and high vertical velocity zones. The positive (negative) vertical velocity magnitude is found to be
approximately O(10−3 ) m/s(O(10−2 ) m/s), one (two) order(s) of magnitude larger than the vertical velocity
outside the sub-mesoscale structures, where the magnitude is stable at O(10−4 ) m/s. The latter value is
consistent with previous numerical and experimental studies that use coarser grid sizes and therefore do not
explicitly calculate the small scale structures. The nonlinear flow introduced by the sub-mesoscale dynamics
within the mixed layer and the non-isotropic grid used in the calculations generates a disparity between the
predicted horizontal wave-number spectra computed using the RSM model with respect to the linear eddy
viscosity model SS. The MS approach improves SS predictions. This improvement is more significant
below the mixed layer in the absence of flow nonlinearities. The horizontal spectra predicted with the RSM
model fits a slope of −3 for large scale structures and a slope between −2 and −5/3 for turbulent structures
smaller than 300 m. This work contributes to the investigation of the physical and methodological aspects
for the detailed modelling and understanding of small scale structures in ocean turbulence. |
| first_indexed | 2024-12-12T10:19:12Z |
| format | Article |
| id | doaj.art-b908abd9af3349bfbf0be2e616d745e9 |
| institution | Directory Open Access Journal |
| issn | 1735-3572 |
| language | English |
| last_indexed | 2024-12-12T10:19:12Z |
| publishDate | 2016-01-01 |
| publisher | Isfahan University of Technology |
| record_format | Article |
| series | Journal of Applied Fluid Mechanics |
| spelling | doaj.art-b908abd9af3349bfbf0be2e616d745e92022-12-22T00:27:36ZengIsfahan University of TechnologyJournal of Applied Fluid Mechanics1735-35722016-01-019418511863.Computational Fluid Dynamics Modelling of a Midlatitude Small Scale upper Ocean FrontPablo Cornejo0Hector H Sepúlveda1University of ConcepciónUnviersity of ConcepciónA numerical model is implemented to describe fluid dynamic processes associated with mid-latitude small- scale (10 km) upper ocean fronts by using modified state of the art computational fluid dynamics tools. A periodic system was simulated using three different turbulent closures: 1) URANS-Reynolds Stress Model (RSM, seven equation turbulence model), 2) LES-Standard Smagorinsky (SS, algebraic model), and 3) LES-Modified Smagorinsky, introducing a correction for non-isotropic grids (MS). The results show the front developing instabilities and generating submesoscale structures after four days of simulation. A strongly unstable shear flow is found to be confined within the mixed layer with a high Rossby number (Ro > 1) and high vertical velocity zones. The positive (negative) vertical velocity magnitude is found to be approximately O(10−3 ) m/s(O(10−2 ) m/s), one (two) order(s) of magnitude larger than the vertical velocity outside the sub-mesoscale structures, where the magnitude is stable at O(10−4 ) m/s. The latter value is consistent with previous numerical and experimental studies that use coarser grid sizes and therefore do not explicitly calculate the small scale structures. The nonlinear flow introduced by the sub-mesoscale dynamics within the mixed layer and the non-isotropic grid used in the calculations generates a disparity between the predicted horizontal wave-number spectra computed using the RSM model with respect to the linear eddy viscosity model SS. The MS approach improves SS predictions. This improvement is more significant below the mixed layer in the absence of flow nonlinearities. The horizontal spectra predicted with the RSM model fits a slope of −3 for large scale structures and a slope between −2 and −5/3 for turbulent structures smaller than 300 m. This work contributes to the investigation of the physical and methodological aspects for the detailed modelling and understanding of small scale structures in ocean turbulence.http://jafmonline.net/JournalArchive/download?file_ID=40250&issue_ID=235Submesoscale; Ocean vertical mixing; Turbulence; Geophysical fluid dynamics. |
| spellingShingle | Pablo Cornejo Hector H Sepúlveda Computational Fluid Dynamics Modelling of a Midlatitude Small Scale upper Ocean Front Journal of Applied Fluid Mechanics Submesoscale; Ocean vertical mixing; Turbulence; Geophysical fluid dynamics. |
| title | Computational Fluid Dynamics Modelling of a Midlatitude Small Scale upper Ocean Front |
| title_full | Computational Fluid Dynamics Modelling of a Midlatitude Small Scale upper Ocean Front |
| title_fullStr | Computational Fluid Dynamics Modelling of a Midlatitude Small Scale upper Ocean Front |
| title_full_unstemmed | Computational Fluid Dynamics Modelling of a Midlatitude Small Scale upper Ocean Front |
| title_short | Computational Fluid Dynamics Modelling of a Midlatitude Small Scale upper Ocean Front |
| title_sort | computational fluid dynamics modelling of a midlatitude small scale upper ocean front |
| topic | Submesoscale; Ocean vertical mixing; Turbulence; Geophysical fluid dynamics. |
| url | http://jafmonline.net/JournalArchive/download?file_ID=40250&issue_ID=235 |
| work_keys_str_mv | AT pablocornejo computationalfluiddynamicsmodellingofamidlatitudesmallscaleupperoceanfront AT hectorhsepulveda computationalfluiddynamicsmodellingofamidlatitudesmallscaleupperoceanfront |