Investigation of clasical and bottom-inlet spillway aerator performances by numerical model

Abstract

The spillways, which are the most important hydraulic elements of the dams, are designed in many different types according to the dam type and flow rates. One of the most important issues to be considered when designing spillways is the design of the aerators. In this study, the cavitational damage on the concrete surface of spillways and the effects of aerators on the cavitation wer investigated. For this purpose, a three-dimensional numerical model of a selected spillway model was prepared and Computational Fluid Dynamics (CFD) analyzes were performed in different Froude numbers. Later, a different type of aerator called as the bottom-inlet aerator was placed in the model and CFD analyzes were performed similar to the original aerators. The results obtained from the CFD analysis were compared with each other and it was concluded that both aerators were sufficiently protected from cavitation damage. The results obtained were also compared with the aerator results obtained with different types and methods in the literature.

Keywords

• Spillway
• Flow 3D
• Aerator
• Cavitation
• Numerical analysis
• CFD

Klasik ve alttan alışlı dolusavak havalandırıcı performanslarının sayısal modelle incelenmesi

Öz

Barajların hidrolik açıdan en önemli elamanı olan dolusavaklar baraj tipine ve geçireceği debilere göre birçok farklı tipte tasarlanmaktadır. Dolusavaklar tasarlanırken dikkat edilmesi gereken en önemli hususlardan biri de kavitasyon önleyici havalandırıcılardır. Bu çalışmada dolusavaklarda beton yüzeyinde oluşan kavitasyon hasarı ve dolusavak havalandırıcılarının kavitasyon üzerindeki etkisi araştırılmıştır. Bu amaçla seçilen bir dolusavağı modelinin üç boyutlu sayısal modeli hazırlanıp farklı Froude sayılarında Hesaplamalı Akışkanlar Dinamiği (HAD) analizleri gerçekleştirilmiştir. Daha sonra farklı bir havakandırıcı tipi olan alttan alışlı havalandırıcı modele yerleştirilerek orijinal havalandırıcılara benzer şekilde HAD analizleri gerçekleştirilmiştir. HAD analizlerinden elde edilen sonuçlar birbirleriyle kıyaslanmış ve her iki havalandırıcının da kavitasyon hasarından yeterince korunduğu sonucuna varılmıştır. Elde edilen sonuçlar ayrıca literatürdeki farklı tip ve yöntemlerle elde edilen havalandırıcı sonuçlarıyla karşılaştırılmıştır.

Anahtar Kelimeler

• Dolusavak
• Flow-3D
• Havalandırıcı
• Kavitasyon
• Sayısal Analiz
• HAD

Kaynakça

1. H. Chanson, Study of air demand on spillway aerator. Journal of Fluid Engineering, 112 (3), 343-350, 1990. https://doi.org/10.1115/1.2909410.
2. P. Volkart, P. Rutschmann, Aerators on spillways in Air Entrainment in Free Surface Flows. Edited by I. R. Wood, A. A. Balkema Publications, Rotterdam, 85-114, 1991.
3. N. L. De S. Pinto, Cavitation and aeration, in Advanced Dam Engineering for Design, Construction, and Rehabilitation. Edited by R.B. Jansen, Kluver Academic Publishers, 620-634, 1988.
4. M. X. Nie, Cavitation prevention with roughened surface. Journal of Hydraulic Engineering, 127 (10), 878-880, 2001. https://doi.org/10.1061/(ASCE)0733-9429(2001)127:10(878).
5. M. A. Kökpınar and M. Göğüş, High-speed jet flows over spillway aerators. Canadian Journal of Civil Engineering, 29 (6), 885-898, 2002. https://doi.org/10.1139/l02-088.
6. M. B. Boes and W. H. Hager, Two-phase flow characteristics of stepped spillways. Journal of Hydraulic Engineering, 129 (9), 661-670, 2003. https:// doi.org/10.1061/(ASCE)0733-9429(2003)129:9(661).
7. M. C. Aydın, Alttan alışlı dolusavak havalandırıcıların CFD analizi. Doktora Tezi, Fırat Üniversitesi Fen Bilimleri Enstitüsü, Elazığ, 2005.
8. M. C. Aydın and M. Öztürk, Verification and validation of a computational fluid ynamics (CFD) model for air entrainment at the spillway aerators. Canadian Journal of Civil Engineering (ISI), 36 (5), 826-836, 2008. https://doi.org/10.1139/L09-017.

9. M. C. Aydın, Aeration efficiency of bottom-inlet aerators for spillways. ISH Journal of Hydraulic Engineering, 24 (3), 330-336, 2018. https://doi.org/ 10.1080/09715010.2017.1381576.
10. H. Y. Chen, W. L. Xu, J. Deng, Z. P. Niu, S. J. Liu and W. Wang, Theoretical and experimental studies of hydraulic characteristics of discharge tunnel with vortex drop. Journal of Hydrodynamics, 22 (4), 582–589, 2010. DOI: 10.1016/S1001-6058(09)60091-3.
11. J. M. Zhang, J. G. Chen, W. L. Xu, Y. R. Wang and G. J. Li, Three-dimensional numerical simulation of aerated flows downstream sudden fall aerator expansion-in a tunnel. Journal of Hydrodynamics, Ser. B, 23 (1), 71-80, 2011. DOI: 10.1016/S1001-6058(10)60090-X.
12. M. Pfister and H. Chanson, Two-phase air-water flows: Scale effects in physical modeling. Journal of Hydrodynamics, 26 (2), 291-298, 2014. https://doi.org/ 10.1016/S1001-6058(14)60032-9.
13. A. Kamel and I. Abdulhameed, Study the Effect of Spillway Locations on the Hydraulic Properties of Spillway. Ciência e Técnica Vitivinícola, 31 (5), 90-106, 2016.
14. C. K. Novakoski and R. F. Hampe, E. Conterato, M. G. Marques and E. D. Teixeira, Longitudinal distribution of extreme pressures in a hydraulic jump downstream of a stepped spillway. Brazilian Journal of Water Resources, 22 (42), 1-8, 2019. https://doi.org/ 10.1590/2318-0331.0117160035.
15. R. Daneshfaraz, A. Ghaderi, A. Akhtari, and S. Di Francesco, On the effect of block roughness in ogee spillways with flip buckets. Fluids, 5 (4), 182, 2020. https://doi.org/10.3390/fluids5040182.
16. H. Chanson, Flow downstream of aerator-aerator spacing, Journal of Hydraulic Research, 27(4), 519-536, 1989. https://doi.org/10.1080/00221688909499127.
17. P. Volkart and A. Chervet, Air slots for flow aeration- determination of shape, size and spacing of air slots for the San Roque Dam Spillway, Mitteilungen der Versuchsanstalt für Wasserbau, Hydrologia und Glaziologie, No. 66, Zürich, Switzerland, 1983.
18. J. A. Kells and C. D. Smith, Reduction of cavitation on spillways by induced air entrainment, Canadian Journal of Civil Engineering, 18(3), 358-377, 1991. https://doi.org/10.1139/l91-047.
19. P. Rutschmann and W. H. Hager, Design and performance of spillway chute aerators, International Water Power and Dam Construction, 42(1), 36-42, 1990.
20. J. Cassidy and R. Elder, Spillways of high dams, in Developments in Hydraulic Engineering 2, Edited by P. Novak, Applied Science Publishers Ltd. Essex, UK, 153-173, 1984.
21. Hidrodizayn, Alparslan II Barajı ve HES Projesi Dolusavak Hidrolik Hesap Raporu. ENERGO-PRO, Murat Nehri Enerji Üretim A.Ş, 2018.
22. Flow Science, FLOW-3D User Manual. Theory Guide, 2016.
23. M. Pfister and W. H. Hager, Chute aerators II: Hydraulic design, J. Hydraul. Eng. 136, 360-367, 2010. https://doi.org/10.1061/(ASCE)HY.1943-7900.0000201.
24. M. R. Özdemir, Dolusavak Havalandırıcılarının Sayısal Modelle İncelenmesi, Yüksek Lisan Tezi, Bitlis Eren Üniversitesi, Fen Bilimleri Enstitüsü, 74s, 2021.