dorsal/arxiv
View SchemaImplementation of the LANS-alpha turbulence model in a primitive equation ocean model
| Authors | Matthew W. Hecht, Darryl D. Holm, Mark R. Petersen, Beth A. Wingate |
|---|---|
| Categories | |
| ArXiv ID | physics/0703195 |
| URL | https://arxiv.org/abs/physics/0703195 |
| DOI | 10.1016/j.jcp.2008.02.018 |
Abstract
This paper presents the first numerical implementation and tests of the Lagrangian-averaged Navier-Stokes-alpha (LANS-alpha) turbulence model in a primitive equation ocean model. The ocean model in which we work is the Los Alamos Parallel Ocean Program (POP); we refer to POP and our implementation of LANS-alpha as POP-alpha. Two versions of POP-alpha are presented: the full POP-alpha algorithm is derived from the LANS-alpha primitive equations, but requires a nested iteration that makes it too slow for practical simulations; a reduced POP-alpha algorithm is proposed, which lacks the nested iteration and is two to three times faster than the full algorithm. The reduced algorithm does not follow from a formal derivation of the LANS-alpha model equations. Despite this, simulations of the reduced algorithm are nearly identical to the full algorithm, as judged by globally averaged temperature and kinetic energy, and snapshots of temperature and velocity fields. Both POP-alpha algorithms can run stably with longer timesteps than standard POP. Comparison of implementations of full and reduced POP-alpha algorithms are made within an idealized test problem that captures some aspects of the Antarctic Circumpolar Current, a problem in which baroclinic instability is prominent. Both POP-alpha algorithms produce statistics that resemble higher-resolution simulations of standard POP. A linear stability analysis shows that both the full and reduced POP-alpha algorithms benefit from the way the LANS-alpha equations take into account the effects of the small scales on the large. Both algorithms (1) are stable; (2) make the Rossby Radius effectively larger; and (3) slow down Rossby and gravity waves.
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"abstract": "This paper presents the first numerical implementation and tests of the\nLagrangian-averaged Navier-Stokes-alpha (LANS-alpha) turbulence model in a\nprimitive equation ocean model. The ocean model in which we work is the Los\nAlamos Parallel Ocean Program (POP); we refer to POP and our implementation of\nLANS-alpha as POP-alpha. Two versions of POP-alpha are presented: the full\nPOP-alpha algorithm is derived from the LANS-alpha primitive equations, but\nrequires a nested iteration that makes it too slow for practical simulations; a\nreduced POP-alpha algorithm is proposed, which lacks the nested iteration and\nis two to three times faster than the full algorithm. The reduced algorithm\ndoes not follow from a formal derivation of the LANS-alpha model equations.\nDespite this, simulations of the reduced algorithm are nearly identical to the\nfull algorithm, as judged by globally averaged temperature and kinetic energy,\nand snapshots of temperature and velocity fields. Both POP-alpha algorithms can\nrun stably with longer timesteps than standard POP.\n Comparison of implementations of full and reduced POP-alpha algorithms are\nmade within an idealized test problem that captures some aspects of the\nAntarctic Circumpolar Current, a problem in which baroclinic instability is\nprominent. Both POP-alpha algorithms produce statistics that resemble\nhigher-resolution simulations of standard POP.\n A linear stability analysis shows that both the full and reduced POP-alpha\nalgorithms benefit from the way the LANS-alpha equations take into account the\neffects of the small scales on the large. Both algorithms (1) are stable; (2)\nmake the Rossby Radius effectively larger; and (3) slow down Rossby and gravity\nwaves.",
"arxiv_id": "physics/0703195",
"authors": [
"Matthew W. Hecht",
"Darryl D. Holm",
"Mark R. Petersen",
"Beth A. Wingate"
],
"categories": [
"physics.ao-ph",
"nlin.CD",
"physics.flu-dyn"
],
"doi": "10.1016/j.jcp.2008.02.018",
"title": "Implementation of the LANS-alpha turbulence model in a primitive equation ocean model",
"url": "https://arxiv.org/abs/physics/0703195"
},
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