مطالعه عددی مقایسه‌ای گردش آب در خلیج فارس با بهره‌گیری از طرح‌واره‌های تلاطمی مختلف

نوع مقاله : مقاله پژوهشی‌

نویسندگان

1 استادیار، گروه علوم پایه، دانشگاه آزاد اسلامی واحد آستارا، آستارا، ایران

2 استاد، مؤسسه ژئوفیزیک دانشگاه تهران، تهران، ایران

چکیده

پیچیده بودن فرآیند اختلاط تلاطمی در خلیج فارس که یک دریای نیمه بسته است باعث می‌شودمی شود که این دریا گزینه مناسبی برای آزمودن عملکرد طرح‌واره تلاطمی در شبیه‌سازی عددی گردش آب در آن باشد. محاسبه یا پیش‌بینی جریان آن ها در این محیط‌ها و گردش آب با در نظردرنظر گرفتن مسئله تلاطم از همه نظر مهم است به عنوان مثال از نظر پخش آلودگی‌ها، زیست‌محیطی، شیلاتی، کشتیرانی، و حتی نظامی در این مطالعه، مدل عددی سه بعدی COHERENS برای شبیه‌سازی گردش آب در خلیج فارس مورد استفاده قرار گرفته است. از دستگاه سیستم مختصات دکارتی برای راستای افقی و از دستگاه ازسیستم مختصات سیگما با 10 لایه برای راستای قائم استفاده شده است. خط ساحلی خلیج فارس و عمق آن بر اساس داده‌های عمق سنجی به دست آمده است. چهار طرح‌واره تلاطمی به جهت آزمودن عملکرد آن‌هاا به مدل اعمال شده است. طرح‌واره‌های اعمال شده شامل دو طرح‌واره بستار تلاطمی k-l و κ-ε و دو طرح‌واره جبری پاکانووسکی و فیلاندر (P-P) و طرح‌وار وابسته به جریان (جریان(f-d) می‌باشد. در شبیه‌سازی گردش آب در خلیج فارس، پارامترها‌ شوری و دما و الگوهای جریانات در سطح و کف، تکامل زمانی دما­شیب، تکامل زمانی شوری و پارامتر‌های تلاطمی از جمله انرژی جنبشی تلاطمی و آهنگ و اتلاف انرژی و طول اختلاط و وشکسانی  پیچکی و پخش پیچکی با اعمال این چهار طرح‌واره مورد مطالعه قرار گرفته‌اند. نتایج بیانگر این است که حساسیت بیشتر عملکرد طرح‌واره‌ها در برآورد پارامتر‌های تلاطمی است و شبیه‌ سازی الگوهای جریان و تاوایی در راستای افق، حساسیت کمتری در مقابل عملکرد طرح‌واره‌های مختلف تلاطمی نشان می‌دهند.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

A comparative numerical study of water circulation in the Persian gulf using different turbulence schemes

نویسندگان [English]

  • Mastaneh Mohandesi Namin 1
  • Abbas_Ali Aliakbari Bidokhti 2
1 Assistant Professor, Mathematics department, Astara branch, Islamic Azad University, Astara, Iran
2 Professor, Institute of Geophysics, University of Tehran, Iran
چکیده [English]

The complex process of turbulent mixing in the Persian Gulf which is a semi-closed sea makes it a good option for testing the performance of different turbulence schemes in the numerical simulation of water circulation in it.
    Calculating or predicting the flow and water circulation in such semi-enclosed sea, by taking the turbulence into account, is important in every respect, for example in terms of spread of contaminations, environmental, fisheries, shipping, and even the military. In this study, the 3D ocean model COHERENS (COupled Hydrodynamical Ecological model for REgioNal
Shelf seas) is used for water circulation simulation of the Persian Gulf. Cartesian coordinate system is used for horizontal direction and sigma coordinate with 10 layers is used for the vertical direction. Persian Gulf coastline and its bathymetry are based on ETOPO-2 data, which are obtained from the digital data of seabed and bulge of the earth with latitudinal and longitudinal geographical two-minute networks. The model is forced by climatologic monthly mean atmospheric forcing at 10-m reference height above ground derived from 54 years (1948–2002) of National Oceanic and Atmospheric Administration (NOAA) data. The advection scheme that is used for momentum and scalars is either total variation diminishing (TVD) scheme, which uses the super bee limiter. The uniform bottom friction coefficient was chosen at 0.005 (m/s) and uniform value for the bottom roughness length that was chosen as 0.015 (m), based on the bottom roughness of the basin. Four turbulence schemes are implemented in the model to test their performance. These include two turbulence closure schemes of k-ε, k-l (Mellor–Yamada), and two algebraic schemes of Pacanowski and Philander and flow-dependent scheme. For the k-ε and k-l models, we used one-equation model for transport equation, the “Blackadar” formulation for mixing length, and limiting conditions for turbulence variables are enabled. The stability functions are expressed in terms of the Richardson number. In the numerical simulation of water circulation in the Persian Gulf, the turbulence schemes are studied to investigate salinity and temperature parameters, flow patterns in the surface and bottom, meso-scale eddies and turbulence parameters including the turbulent kinetic energy and energy dissipation rate, the mixing length, eddy adhesion and eddy diffusivity. The model has been successful in simulating the intrusion of low salinity waters into the Persian Gulf and baroclinic instability and the formation of mesoscale eddies in the center of the basin. In comparison between the performance of schemas, the results show that the schemes are very sensitive in estimating the turbulence parameters and simulation of flow patterns, vorticity, salinity and temperature, show less sensitivity to the performance of various turbulence schemes.

کلیدواژه‌ها [English]

  • Turbulence schemes
  • water circulation
  • COHERENS model
  • Persian Gulf
رودی، ولفگانگ. 1388. مدل‌های آشفتگی و کاربردهای آن در هیدرولیک:  موسسه انتشارات دانشگاه صنعتی خواجه‌نصیرالدین طوسی.
Alessi, C.A., Hunt, H.D., Bower, A.S., 1999, Hydrographic data from the U.S. naval oceanographic office, Persian Gulf, Southern Red Sea, and Arabian Sea 1923-1996: Woods Hole Oceanographic Institution, USA. 74P.
 
 
Souza de, J. L., Lima de A. L., Rota de Oliveira, I., Dias Soares, and Magalhaes Mata, M., 2013, Incorporation of new turbulent closure schemes in the Princeton ocean model (pom): Revista Brasileira de Geofisica, 31(1),17–30.
Bidokhti, A. A. and Ezam, M.,2009, The Structure of the Persian Gulf outflow subjected to density variations: Ocean Science, 5, 1–12.
Blackadar, A. K, 1962, The vertical distribution of wind and turbulent exchange in a neutral atmosphere: Journal of Geophysical Research, 67, 3095-3102.
Bowden K. F., Fairbairn L. A. and Hughes P., 1959, The distribution of shearing stresses in a tidal current: Geophysical Journal of the Royal Astronomical Society, 2, 288–305.
Davies A. M., 1990, On extracting tidal current profiles from vertically integrated twodimensional hydrodynamic models: Journal of Geophysical Research, 95, 18317–18342.
Davies A.M., 1993. A bottom boundary layer-resolving three-dimensional tidal model :
A sensitivity study of eddy viscosity formulation: Journal of Physical Oceanography,
23, 1437–1453.
Durski,S. M., Glenn,S. M., and Haidvogel, D. B., 2004, Vertical mixing schemes in the coastal ocean, Comparison of the level 2.5 Mellor-Yamada scheme with an enhanced version of the K profile parameterization: Journal of Geophysical Research, vol 109.
 Galperin, B., Kantha, L. H., Hassid, S. and Rosati, A. A, 1988, quasi-equilibrium turbulent energy model for geophysical flows: Journal of the Atmospheric Sciences, 45, 55-62.
Glorioso P. D. and Davies A. M., 1995, The influence of eddy viscosity formulation, bottom topography, and wind wave effects upon the circulation of a shallow bay: Journal of Physical Oceanography, 25, 1243–1264.
Ilıcak, M., Ozgokmen,T. M., Peters, H., Baumert, H. Z., and Iskandarani, M, 2008, Performance of two-equation turbulence closures in three-dimensional simulations of the Red Sea overflow: Ocean Modelling 24, 122-139.
 Li, X., Chao, Y., McWilliams, J. C., and Lueng Fu, L. A., 2001, Comparison of Two Vertical-Mixing Schemes in a Pacific Ocean General Circulation Model: Journal of climate, Volume 14(7), 1377–1398.
Liu, W. C. Chen, W. B. Hsu, M. H., 2010, Application of different turbulence closure model to investigate residual current and salinity in an estuary: Journal of Coastal and Ocean Eng, 10,1-24.
Luyten,P .J., Deleesnijder, E., Ozer, J., and Ruddick, K. G., 1996, Presentation of a family of turbulence closure models for stratified shallow water flows and preliminary application to the Rhine outflow region: Continental Shelf Res, 16,101-130.
Mellor G.L. and Yamada T., 1982. Development of a turbulence closure model for geophysical
fluid problems: Reviews of Geophysics and Space Physics, 20, 851–875.
Mohandesi Namin, M., Bidokhti, A. A., Karami Khaniki, A., Torabi Azad, M., and Hasan zadeh, I,2017, Estimation of Turbulence Parameters in a Shallow Sea Using Numerical Simulation with Sensitivity to Vertical Mixing Parameterization: Indian journal of Geo Marine Science, 46(09), 1788-1798.
Obino, R. S., Chu, P. C., and Haeger, S. D., 2002, Simulation of the Bohai Sea Circulation and Thermohaline Structure Using COHERENS Model, Master’s Thesis: NAVAL Postgraduate School, Monterey.
Pacanowski R. C., and Philander S. G. H., 1981, Parameterization of vertical mixing in numerical models of tropical oceans: Journal of Physical Oceanography, 11, 1443–1451.
Semtner, A. J., and Chervin, R. M., 1988, A simulation of the global ocean circulation with resolved eddies: Journal of Geophysical Research-Oceans, 93, 15502-15522.
Ttuomi, L., and Myrberg, K., 2011, The performance of vertical turbulence models in the modeling of hydrodynamics in the Baltic Sea: Geophysical Research Abstracts 13, 6662.
Wijesekera, H. W., Allen, J. S., and Newberger,P. A., 2003, Modeling study of turbulent mixing over the continental shelf, Comparison of turbulent closure schemes: Journal of Geophysical Research, 108 (c3), 3103.