İnce Kenarlı Savaklardaki Havalandırma Verimliliğinin Deneysel Olarak İncelenmesi: Debi Etkisi

Yıl 2023, Cilt: 8 Sayı: 4, 736 - 741, 31.12.2023

Serhat Küçükali

https://doi.org/10.35229/jaes.1402216

Öz

Bu deneysel çalışmada savakların havalandırma performansı debi etkisi altında incelenmiştir. Bu amaçla, düşme yükseklikleri 0,35-0,535 m arasında ve birim genişlikten geçen debinin 0,03-0,063 m2/s aralığında değişen 90° üçgen ince kenarlı bir savakta deneyler yapılmıştır. Deneysel verilerin analizi sonucu, birim genişlikten geçen ile havalandırma verimliliği arasında pozitif bir korelasyon bulunmuş ve ortaya çıkan ilişki, düşme yüksekliği ve birim genişlikten geçen debinin fonksiyonu olarak tanımlanmıştır. Havalandırma verimliliği yük kaybının 3/4’cü, birim genişlikten geçen debinin ise 1/3’cü üssü ile ilişkilendirilmiştir. Önerilen ampirik formülün tahmin kapasitesi diğer ampirik formüllerle ortalama bağıl hata değerleri açısından karşılaştırılmıştır. Ayrıca düşüm yüksekliğinin yük kaybına eşit olduğu varsayıldığında, hidrolik sırçamdaki havalandırma verimliliğinin yük kaybında olan bağımlığının ince kenarlı savakta da geçerli olduğu gözlemlenmiştir.

Anahtar Kelimeler

İnce kenarlı savak, doğal havalandırma, çözünmüş oksijen, düşüm yüksekliği, debi etkisi

An Experimental Investigation on Aeration Performance of Sharp-crested Weirs: Discharge Effect

Öz

In this experimental study, the aeration performance of weirs was investigated by means of the discharge effect. For this purpose, experiments were performed at a 90º V-notch weir with drop heights ranging from 0.35-0.535 m and unit discharges ranging from 3x10-2 to 6.33x10-2 m2/s and E20 varied in the range of 0.13-0.23. A positive correlation was found between the unit discharge and aeration efficiency and the resulting relationship was defined by a power function in terms of drop height and unit discharge. It was found that aeration efficiency is in proportion to the 3/4 power of drop height and 1/3 power of unit discharge. The proposed empirical formula prediction capacity has been compared with the other empirical formulas in terms of their average relative error values. Additionally, by assuming a drop height equal to head loss, it was observed that hydraulic jump aeration efficiency dependence on head loss continued for weirs indicating the free-surface macro turbulence's main role in the process.

Anahtar Kelimeler

sharp-crested weir, self-aeration, dissolved oxygen, drop height, discharge effect

Kaynakça

• Apted, R.W. & Novak, P. (1973). Oxygen uptake at weirs. Proceedings of 15th IAHR Congress, Istanbul, Türkiye, 177-186.
• Avery, S. T. & Novak, P. (1978). Oxygen transfer at hydraulic structures. J. Hydr. Div., ASCE, 104(11), 1521-1540.
• Dankwerts, P.V. (1951). Significance of liquid-film coefficients in gas absorption. Industrial and Engineering Chemistry, 43(6), 1460-1467.
• Ervine, D.A., Mckeogh, E. & Elsawy, E.M. (1980). Effect of turbulent intensity on the rate of entrainment by plunging water jets. Proc. Inst. Civ. Engrs., 2, 425-455.
• Ervine, D.A. (1998). Air entrainment in hydraulic structures: a review. Proc. Instn Civ. Engrs Wat., Marit. & Energy., 130(5), 142-153.
• Giller, P.S. & Malmqvist, B. (1998). The biology of streams and rivers, Oxford University Press, Great Britain.
• Gulliver, J.S., Wilhelms S.C. & Parkhill, K.L. (1998). Predictive capabilities in oxygen transfer at hydraulic structures. Hydr. Engrg., ASCE, July, 664-671.
• Gulliver, J.S. & Rindels, A.J. (1990). Indexing gas transfer in self-aerated flows. J. Envir. Engrg., ASCE, 116(3), 503-523.
• Gameson, A.L.H., Vandyke, K.G. & Ogden, C.G. (1958). The effect of temperature on aeration at weirs. Water and Water Engrg., Nov, 489-492.
• Higbe, R. (1935). On the adsorption of a pure gas into a still liquid during short period of exposure. Transactions, American Institute of Chemical Engineers, 31, 365-390.
• ISO. (2008). Hydrometry-Open channel flow measurement using thin-plate weirs, Geneva, Switzerland.
• Kawase, Y. & Young, M.M. (1992). Correlations for liquid-phase mass transfer coefficients in bubble column reactors with Newtonian and nonnewtonian fluids. The Can. J. Chem. Engrg., 70, 48-54.
• Kim J. & Walters, R.W. (2001). Oxygen transfer at low drop weirs. J. Envir. Engrg, ASCE, 127(7), 604- 610.
• Kobus, H. (1991). Introduction to air-water flows. Air entrainment in free surface flows, I. R. Wood, ed., IAHR Hydraulic Structures Manual, No. 4, Rotterdam.
• Kucukali, S. (2006). Investigation of hydraulic jumps aeration efficiency in terms of head loss concept. Ph.D. thesis, Istanbul Technical University, Istanbul, (In Turkish).
• Kucukali, S. & Cokgor, S. (2009). Energy concept for predicting hydraulic jump aeration efficiency. J. Envir. Engrg., ASCE, 135(2), 105-107.
• Kucukali, S. & Cokgor, S. (2020). An experimental ınvestigation of reaeration and energy dissipation in hydraulic jump, M. B. Kalinowska, ed., Recent Trends in Environmental Hydraulics, 127-136, Cham, Switzerland, Springer.
• Muntz, C. & Roberts, P.V. (1989). Gas and liquid phase mass transfer resistances of organic compounds during mechanical surface aeration. Wat. Res., 23(5), 589-601.
• Markosfky, M. & Kobus, H., 1978. Unified presentation of weir-aeration data. J. Hydr. Engrg., ASCE, 104(4), 562-568.
• Nakasone, H. (1987). Study of aeration at weirs and cascades. J. Envir.Engrg, ASCE, 113, 64-81. Rajwa-Kuligiewicz, A., Bialik, R.J. & Rowiński, P. (2016). Experimental investigations on the oxygen transfer efficiency at low-head hydraulic structures, P. Rowiński, ed., Hydrodynamic And Mass Transport At Freshwater Aquatic Interfaces, GeoPlanet: Earth and Planetary Sciences. Springer, Cham.
• Sene, K.J., Hunt, J.C.R. & Thomas, N.H. (1994). The role of coherent structures in bubble transport by turbulent shear flows. J. Fluid Mechanics, 259, 219-240.
• Streeter, V.L. & Wylie, E.B. (1981). Fluid mechanics, McGraw-Hill, Singapore.
• Toombes, L. & Chanson, H. (2005). Air-water mass transfer on a stepped waterway. J. Envir. Engrg., ASCE, 131(10), 1377-1386.
• Urban, A.L., Wilhelms, S.C. & Gulliver, J.S. (2005). Decay of turbulence downstream of a stilling basin. J.Hydr. Engrg., ASCE, 131(9), 825-829.
• Van der Kroon, G.T.M. & Scharm, A.H. (1969). Weiraeration-Part II. H2O, 22, 538-545. Watson, C.C., Walters, R.W. & Hogan, S.A. (1998). Aeration performance of low drop weirs. J. Hydr. Engrg., ASCE, 124(1), 65-71.
• Wei, T. & Willmarth, W.W. (1989). Reynolds-number effects on the structure of a turbulent channel flow. J. Fluid Mech., 204, 57-95.
• Welch, E.B. & Jacoby, J.M. (2004). Pollutant effects in freshwater: Applied limnology, Spon Press, London and New York.
• Zhao,W., Prata, A., Peirson, W., Stuetz, R. & Felder, S. (2022). Reaeration in supercritical open channel flows: An experimental study. Journal of Hydraulic Engineering, 148, DOI: 10.1061/(ASCE)HY.1943-7900.0002001.