Hydraulic investigation and design of roof profile of an orifice spillway using experimental and numerical models

Abstract

The roof profile of an orifice spillway plays an important role in deciding its discharging capacity. The necessary requirement is that the profile should not experience excessive negative pressures and should be simple to construct. It is found from the literature that the flow through orifice spillway at the entrance does not follow an elliptical roof profile recommended by United States Bureau of Reclamation. During the regime of flow with high heads, flow separation takes place on the orifice roof profile resulting in reduced discharging capacity. It is also found that there is no specific design method available for design of orifice spillway roof profile with respect to the upstream head as well as other parameters. The main aim of the present study is to develop an equation for design of the roof profile of an orifice spillway. Computational fluid dynamics software FLUENT version 6.3.26 was used for the numerical simulations. The numerical model was verified and validated by comparing the results with the physical model. An equation for the design of roof profile was developed after analyzing the observed discharge through orifice, pressures on spillway bottom profile and upper nappe profile of an orifice spillway. The proposed equation was verified with the data which have not been used in deriving the equation. The proposed equation was also validated in terms of coefficient of discharge and pressure distribution on the bottom and roof profile with the existing data of some other real-life orifice spillways. The results are encouraging indicating that the developed equation can be used to get roof profile of an orifice spillway, which can be used at the design stage of an orifice spillway.

Keywords:

• numerical model
• orifice spillway
• physical model
• roof profile
• equation for design

Acknowledgements

The authors are grateful to the Director, CWPRS for the facility provided to conduct physical model studies in the CWPRS, Pune, India.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Notes on contributors

Prajakta P. Gadge

Mrs Prajakta P. Gadge is working at present as Sc B in the CWPRS. She has acquired Bachelor of Civil Engineering in 2001 from Nagpur University and Master in Hydraulic Engineering in 2011 from University of Pune, India. Currently, she is pursuing PhD in Civil Engineering from IIT Bombay. She has about 11 years of experience in evolving efficient hydraulic design of spillway, energy dissipators, powerhouse tailrace channels for several dams in India and abroad. She has worked on hydraulic model studies for more than 15 projects. Few projects of national importance are Parbati stage-II, Punatsangchhu stage-I (Bhutan), Pare, Subansiri, Kishanganga, Omkareshwar, Myntdu, Chhukha, etc. Studies conducted include both physical and numerical models. Numerical modeling based on the CFD technique for simulation of flows over hydraulic structures is becoming popular recently. She has used this technique for the simulation of flow over orifice spillway for her PhD studies. She has presented a paper in IAHR – APD Congress held at Hanoi, Vietnam in 2014. She has published about 10 technical papers in National and International Journals and contributed in more than 20 technical reports. She is a life member of Indian Society for Hydraulics.

V. Jothiprakash

Prof. V. Jothiprakash is currently working in the Department of Civil Engineering, Indian Institute of Technology Bombay, Powai, since August 2005. Earlier he worked at the National Institute of Technology, Tiruchirappalli (2004–2005). He obtained his PhD from the Indian Institute of Technology Madras, Chennai, India in 2000. His research interest includes Water Resources Systems Analysis, Soft computing techniques, Stochastic Hydrological Modeling, Reservoir Sedimentation, Genetic Algorithms and Genetic Programming, Nonlinear Dynamics, Singular Spectrum Analysis. He has published more than 274 papers in leading international journals and conferences in his research fields. He has been awarded Young Teacher award by All India Council of Technical Education, Young Engineer by Indian National Academy of Engineering, Technology Development and Best Industrial Project by IIT Bombay. Seven of his papers published in journals have been awarded the best paper award. He has been the special issue editor for ISH Journal of Hydraulic Engineering. He is currently serving as Associate Editor in ISH Journal of Hydraulic Engineering, Taylor & Francis Publications. He is in the editorial member of International Journal of Ground Water Research (IJGWR). He has been a reviewer for more than 40 international journals, including Journal of Hydrology, ASCE Journals, Hydrology Earth Science Systems and Water Resources Research. He has reviewed and served as an oral examiner for more than 25 PhD theses. He is a life member of International Association of Hydrological Science (UK) and Fellow of Indian Association of Hydrologists and Fellow of Indian Society for Hydraulics, Fellow of Institution of Engineers (India) and members of several professional societies.

V. V. Bhosekar

Mrs V. V. Bhosekar is working at present as Sc E in CWPRS. She has acquired Bachelor of Civil Engineering in 1982 and Master in Hydraulic Engineering in 1991 from University of Pune. She completed MS in Hydraulic Engineering from the University of Minnesota, USA in 1992 and PhD from IIT Bombay in 2011. She has about 33 years of experience in evolving efficient hydraulic design of spillway, energy dissipators, powerhouse tailrace channels and sedimentation and flushing of reservoirs for several dams in India and abroad. She has worked on hydraulic model studies for more than 40 projects. A few dam projects of national importance are Sardar Sarovar, Omkareshwar, Salal, Chamera Stages I, II & III, Koyna, Tehri, Kurichu and Punatsangchu (Bhutan), Subansiri, Teesta and Salma (Afghanistan). Studies conducted include both physical and mathematical models. She has published about 60 technical papers in National and International Journals and contributed in more than 100 technical reports and 4 technical memoranda. She is the Chairman of the Subcommittee 6 on ‘Sediment transport’ of International Standard Organization Technical Committee 113 since 2012. She is represented as expert in various national technical committees of Bureau of Indian Standards. She is the Former Member-Secretary of Indian National Committee on Hydraulics. She is a life member of Institution of Engineers and Indian Society for Hydraulics.