Evaluation of the Effect of Thermal Stratification Strength on Artificial De-stratification Efficiency in Reservoirs

Document Type : Research Article

Authors

Abstract

Thermal stratification and mixing can greatly change the water quality in a reservoir during a year. A conventional method to de-stratify the reservoir is using a bubble plume produced by an air diffuser system. If the aeration system designed properly, maximum efficiency can be achieved. In this paper a full three dimensional computational fluid dynamics model using ANSYS Fluent software employed to study the artificial de-stratification process in a laboratory tank. Because of some deficiencies in Fluent software and in order to produce more accurate results, UDF codes were written and added to the CFD model. Based on the results, stratification strength is a critical factor which controls the energy required for mixing the reservoir. It is also concluded that by reducing the amount of gas injected to the reservoir, less energy dissipates through turbulence. Therefore, the efficiency of de-stratification process will increase. According to the results, it is recommended that aeration system should be designed to work when plume number is around 400.

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References

توحیدی، ح. (1377). "تحقیق در رابطه با عوامل موثر در تغییرات کیفی آب مخزن سد طرق و ارائه بهینه کردن آب دریاچه"، کمیته تحقیقات کاربردی شرکت آب منطقه ای خراسان رضوی (وزارت نیرو).
سعیدی، پ.، مهردادی، ن.، آقاشاهی، م. و افضلی، ل. (۱۳۹۱). "شبیه‌سازی دو بعدی رژیم حرارتی مخزن سد شهید رجایی"، ششمین همایش ملی مهندسی محیط زیست، دانشگاه تهران، دانشکده محیط زیست.
سلیمانی، ش.، بزرگ حداد، ا. و سعادت پور، م. (۱۳۹۴). "شبیه‌سازی لایه بندی حرارتی و تعیین رقوم دریچه آبگیری مخزن سد کرخه با استفاده از مدل دو بعدی  CE-QUAL-W2"، دومین همایش یافته‌های نوین در محیط‌زیست و اکوسیستم‌های کشاورزی، دانشگاه تهران، پژوهشکده انرژی‌های نو و محیط زیست.
کیانوش، ب. (1394). "استفاده از روش عددی حجم محدود جهت مدل­سازی سه بعدی اختلاط مصنوعی در مخازن سدها با لایه­بندی حرارتی"، پایان‌نامه کارشناسی ارشد مهندسی آب (هیدرولیک)، دانشگاه صنعتی خواجه نصیرالدین طوسی.
Armengol, J., Crespo, M., Morgui, J. A., and Vidal, A. (1987). "Phosphorus budget and forms of phosphoros in the Sau Reservoir sediment: an interpretion of the limnological record". In Paleolimnology IV (pp. 331-336). Springer Netherlands.
Asaeda, T., and Imberger, J. (1993). "Structure of bubble plumes in linearly stratified environments". Journal of Fluid Mechanics, 249, pp. 35-57.
Cloete, S. W. P., et al. (2013). "A numerical modelling investigation into design variables influencing mixing efficiency in full scale gas stirred ladles". Minerals Engineering 46, pp. 16-24.
Etemad-Shahidi, A., Faghihi, M., and Imberger, J. (2010). "Modelling thermal stratification and artificial de-stratification using DYRESM", Case Study: 15-Khordad Reservoir.
FLUENT, "ANSYS FLUENT Theory Guide," (2013).
Ford. D. E., and Thornton, K.W. (1979). "Time and length scales for the one-dimensional assumption and its relation to ecological models". Water Resources Res., 15(1), pp. 113-120.
Mcdougall, T. J. (1978). "Bubble plumes in stratified environments". Journal of Fluid Mechanics, 85(04), pp. 655-672.
Olsen, J. E., and Popescu, M. (2012, December). "On the effect of lift forces in bubble plumes". In proceedings of Ninth International Conference on CFD in the Minerals and Process Industries.
Reynolds, C.S. (1992). "Daynamics, selection and composition of phytoplankton in relation to vertical structure in lakes". Arch Hidrobiol. Beih Ergbn. Limnologie, 35, pp. 13-31.
 
Sherman, B. (2000). Scoping options for mitigating cold water discharges from dams, Canberra, CSIRO Land and Water.
Soga, C. and C. Rehmann (2004). "Dissipation of turbulent kinetic energy near a bubble plume". Journal of Hydraulic Engineering 130(5), pp. 441-449.
Yum, K., Kim, S. H., and Park, H. (2008). "Effects of plume spacing and flowrate on destratification efficiency of air diffusers". Water Research, 42(13), pp. 3249-3262.

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History

  • Receive Date: 04 February 2016
  • Revise Date: 17 July 2016
  • Accept Date: 30 August 2016

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