Determination the Location of an Air Inception Point for Different Configurations of Stepped Spillways using CFD


  • Zaid P. O Department of Water resources, College of Engineering, Salahaddin University-Erbil, Kurdistan Region, Iraq
  • Abo A. A Department of Water resources, College of Engineering, Salahaddin University-Erbil, Kurdistan Region, Iraq



Fluent, VOF, Inception point, Stepped spillway, Realizable k-ԑ Model, CFD.


The goal of this research is to assess the impact of various factors on the position of the inception point for a stepped spillway, such as the number of steps, step angles, and discharges. It is feasible to determine the place of conception in this study using the computational fluid dynamics code Fluent. The volume of fluid (VOF) model is used to simulate air-water interaction on the free surface, and the turbulence closure is calculated using the realizable  model. The code was tested against published experimental data of (Hunt and Kadavy 2009) for this purpose. The results of the ANSYS-fluent code compared with aforementioned experimental data and it match the experimental data. Then, the impact of the aforementioned factors on the location of an air inception point and its length were next investigated by simulating 45 cases in total.


Abo, A., 2013. A three-dimensional flow model for different cross-section high-velocity channels (Doctoral dissertation, University of Plymouth).

Amador, A., Sánchez-Juny, M. and Dolz, J., 2006. Characterization of the nonaerated flow region in a stepped spillway by PIV.

Chanson, H., 1996. Air bubble entrainment in free-surface turbulent shear flows. Elsevier.

Chanson, H. and Toombes, L., 2001. Strong interactions between free-surface aeration and turbulence down a staircase channel.

Chakib, B., 2013. Numerical computation of inception point location for flat-sloped stepped spillway. International Journal of Hydraulic Engineering, 2(3), pp.47-52.

Hunt, S.L. and Kadavy, K.C., 2010. Energy dissipation on flat-sloped stepped spillways: Part 2. Downstream of the inception point. Transactions of the ASABE, 53(1), pp.111-118.

Ohtsu, I., Yasuda, Y. and Takahashi, M., 2004. Flow characteristics of skimming flows in stepped channels. Journal of hydraulic Engineering, 130(9), pp.860-869.

Raza, A., Wan, W. and Mehmood, K., 2021. Stepped Spillway Slope Effect on Air Entrainment and Inception Point Location. Water, 13(10), p.1428.

Wan, W., Raza, A. and Chen, X., 2019. Effect of height and geometry of stepped spillway on inception point location. Applied Sciences, 9(10), p.2091.

Zhang, G. and Chanson, H., 2016. Hydraulics of the developing flow region of stepped spillways. I: Physical modeling and boundary layer development. Journal of Hydraulic Engineering, 142(7), p.04016015.

Zhang, J., Chen, J. and Wang, Y., 2012. Experimental study on time-averaged pressures in stepped spillway. Journal of Hydraulic Research, 50(2), pp.236-240.





Mathematics ,Physics and Engineering Researches