Numerical and experimental study of pitched steps effects in stepped spillway on the hydraulic parameters and energy dissipation in the skimming flow

Document Type : Research Article


1 2- Ph.D. of Hydraulic Structures, Water Engineering Department, Faculty of Civil Engineering, Tabriz University, Tabriz, Iran.

2 Civil Engineering Department, Tabriz University, Tabriz, Iran.


One of the most prominent features of the stepped spillway performance is the considerable loss of energy during it compared with other types of spillway. Considering this feature, obtaining a more detailed view on the energy dissipation parameter and, finally, increasing its amount has been the focus of most studies related to this type of spillway. For this purpose, using a Flow-3D model, the effect of pitched steps (steps with hole) on the velocity and pressure variations, water height at downstream and energy dissipation has been investigated. As well as the appropriate model of the most energy dissipation in the laboratory was developed and studied. Numerical and experimental results show that pitched steps reduces the velocity to about (82-69%) and reduces the water height at the downstream by up to 33%, and the energy dissipation is increased to about 4 times. According to the pressure distribution profiles at the vertical edge of the step, it was observed that the amount of negative pressure in the vertical wall decreased by about 82%, and the positive pressure was approximately increased by 3 and 4 times. The negative pressure on the floor of the steps is turned into positive and the positive pressure near the edge is increased due to the presence of the hole. Also, the results showed that the error rate of the studied parameters in the numerical and experimental models was very low and acceptable, indicating a good fit between numerical and experimental data.


Main Subjects

[1]M.W. Horner, An analysis of flow on cascades of steps, University of Birmingham, 1969.
[2]G.C. Christodoulou, Energy dissipation on stepped spillways, Journal of Hydraulic Engineering, 119(5) (1993) 644-650.
[3]F. Salmasi, M. Bina, S.A. Mousavi Jahromi, Estimating of flow loss over stepped spillway using physical model, Journal of Agriculture, 26 (2003) 57-71.
[4]H. Mohammad Vali Samani, M.R. Nazarzadeh, Evaluation of Hydraulic Principles governing on Flow and Design of Stepped spillways, Journal of Technical School, 38(2) (2004) 339-347.
[5]H. Torabi, A. Parsaie, H. Yonesi, E. Mozafari, Energy dissipation on rough stepped spillways, Iranian Journal of Science and Technology, Transactions of Civil Engineering, 42(3)(2018), 325-330.
[6]S. Felder, Ph. Guenther, H. ChansonAir-water flow properties and energy dissipation on stepped spillways: A physical study of several pooled stepped configurations, School of Civil Engineering The University of Queensland, Brisbane QLD 4072, Australia. Report CH87/12 (2012a).
[7]J.J. Cassidy, Irrotational flow over spillways of finite height, University of Missouri-Columbia, 1965.
[8]D. Ho, K. Boyes, S.M. Donohoo, Investigation of spillway behavior under increased maximum flood by computational fluid dynamics technique, in:  14th Australasian Fluid Mechanics Conference, Adelaide University, Adelaide, Australia, 2001.
[9]Q. Chen, G. Dai, H. Liu, Volume of fluid model for turbulence numerical simulation of stepped spillway overflow, Journal of Hydraulic Engineering, 128(7) (2002)683-886 .
[10]M. S´ nchez-Juny, E. Blade, J. Dolz, Pressures on a stepped spillway, Journal of Hydraulic Research, 45(4) (2007) 505511.
[11]K. Roushangar, S. Akhgar, F. Salmasi, Estimating discharge coefficient of stepped spillways under nappe and skimming flow regime using data driven approaches, Flow Measurement and Instrumentation, 59 (2018) 79-87.
[12]K. Morovati, A. Eghbalzadeh, Stepped Spillway Performance: Study of the Pressure and Turbulent Kinetic Energy versus Discharge and Slope.
[13]N. Souri, A. Mojtahedi, Investigating the flow pattern over stepped spillway using numerical and physical model, Tabriz University, 2014.
[14]A. Parsaie, S. Dehdar-Behbahani,  A.H. Haghiabi, Numerical modeling of cavitation on spillway’s flip bucket, Frontiers of Structural and Civil Engineering, 10(4)(2016) 438-444.
[15]Parsaie, A. Moradinejad A.H. Haghiabi, Numerical Modeling of Flow Pattern in Spillway Approach Channel, Jordan Journal of Civil Engineering, 12(1)(2018) 1-9.
[16]S. Dehdar-Behbahani, A. Parsaie ,Numerical modeling of flow pattern in dam spillway’s guide wall. Case study: Balaroud dam, Iran ,Alexandria Engineering Journal, 55(1)(2016) 467-473.
[17]Kh . Morovati, A. · Eghbalzadeh, M. Javan, Numerical investigation of the configuration of the pools on the flow pattern passing over pooled stepped spillway in skimming flow regime Acta  Mechanic 227, 353–366 (2016) DOI 10.1007/s00707-015-1444-x
[18]K. Roushangar, S. Akhgar, F. Salmasi, J. Shiri, Modeling energy dissipation over stepped spillways using machine learning approaches, Journal of Hydrology, 508 (2014) 254-265.
[19]A. Parsaie, A.H. Haghiabi, M. Saneie, H. Torabi, Prediction of energy dissipation on the stepped spillway using the multivariate adaptive regression splines, ISH Journal of Hydraulic Engineering 22(3)(2016) 281-29.
[20]A. Parsaie, A.H. Haghiabi, M. Saneie, H. Torabi, Applications of soft computing techniques for prediction of energy dissipation on stepped spillways, Neural Computing and Applications, 29(12)(2016) 1393-1409.
[21]A. Parsaie, A.H. Haghiabi, M. Saneie, H. Torabi, Prediction of Energy Dissipation of Flow over Stepped Spillways Using Data-Driven Models." Iranian Journal of Science and Technology, Transactions of Civil Engineering, 42(1) (2017) 39-53.
[22]A.H. Haghiabi, H.M. Azamathulla, A. Parsaie, Prediction of head loss on cascade weir using ANN and SVM." ISH Journal of Hydraulic Engineering, 23(1) (2016) 102-110.
[23]N. Souri, A. Mojtahedi, Evaluation of the effects of stepped spillway geometry on the amount of passive energy dissipation using a fuzzy inference system, Journal of Civil and Environmental Engineering, 45(3)(2016).