Industrial Innovations

Industrial Innovations

Numerical Simulation of Secondary Bottom Outlet of RUDBAR Dam in Lorestan to evaluate the Jet Length and Cavitation Risk

Document Type : Original Article

Authors
Maryam Gharibipour 1
Mohsen Nasrabadi 2
Hamed Safikhani 1
Younes Aminpour 3
1 Department of Mechanical Engineering, Faculty of Engineering and Technology, Arak University, Arak, Iran.
2 Department of Water Science and Engineering, Faculty of Agriculture and Environment, Arak University, Arak, Iran.
3 Hydraulic Structures Department, Water Research Institute, Ministry of Energy, Tehran, Iran.
10.66224/jii.4.1.1
Abstract
In this research, the flow behavior in the secondary bottom outlet of the Roudbar- Lorestan Dam was numerically analyzed using ANSYS CFX software, with an emphasis on predicting the length of the issuing jet and the possibility of cavitation occurrence. For validation, the outputs of the numerical model were compared with experimental results obtained from the dam’s reduced-scale physical model (1:20). The meshing process and grid independence study showed that using cubic elements with approximately 900,000 elements could reduce the error in the issuing jet length to less than 8%. After evaluating various turbulence models, the K−ω model was selected as the superior turbulence model with a mean relative error of 7.88%. Furthermore, the results indicated that at the maximum flow rate, the simulated jet length was predicted to be about 22% shorter than the initial design state. Analysis of local pressures and the cavitation index also showed that in the high-velocity flow regions and near the gate, the cavitation index reached a minimum value of 0.78, which is close to the threshold for the occurrence of cavitation. In contrast, the values of this coefficient in the middle and end sections of the jet were higher than 1.2, and the probability of cavitation in these areas was assessed as very negligible. Overall, the findings of this research demonstrate that numerical simulation can be used with high accuracy, exceeding 95%, in predicting the jet length and evaluating cavitation conditions, and is considered an efficient tool for the analysis and optimization of the design of dam bottom outlet.
Keywords
Bottom Outlet
Numerical Simulation
Rudbar-Lorestan Dam
Cavitation
[1] Dargahi B. Flow characteristics of bottom outlets with moving gates. Journal of Hydraulic Research. 2010; 48(4): 476–482. doi:10.1080/00221686.2010.507001.
[2] Nazari S. and Palhang M. Numerical simulation of air–water two-phase flow over dam spillways using CFD. Journal of Hydraulic Research. 2011; 49(3): 366–374.
[3] Water Research Institute. Hydraulic model of the secondary bottom outlet system of Rudbar Lorestan dam (Final Report). 2019.
[4] Ahmadi H. and Nemati M. Numerical investigation of the effect of the curvature of the duct before the service gate of the lower dischargers on the flow hydraulics. Iranian Hydraulic Association, Scientific-Research Journal. 2017; 12(3): 61-68.
[5] Yamini O. A. Mousavi H.S. Kavianpour M.R. Safari Ghaleh R. Hydrodynamic Performance and Cavitation Analysis in Bottom Outlets of Dam Using CFD Modelling. Advances in Civil Engineering. 2021; https://doi.org/10.1155/2021/5529792.
[6] Taheri Aghdam A. Salmasi F. Hosseinzadeh Dalir A. Abbaspour A. Experimental and Numerical Investigation of the Trajectory of Outlet Jets through the Pressurized Discharge Gates of Reservoir Dams. Journal of Water and Sustainable Development. 2023; 10(3): 109-120. https://doi.org/10.22067/jwsd.v10i3.2301-1207.
[7] Tarighi S. Ghasemzadeh P. Jabbari Kalkhoran B. Cavitation Investigation in the Sluice Section of the Sefid Rood Dam Using Flow 3D Software for Environmental Purposes. International Journal of Innovations and Interdisciplinary Research (IJIIR). 2024: 3005-4893.
[8] Ghobadi M. and Moradinia S. Simulation and optimization of hydraulic parameters of turbulent flow in lower dam spillways using Open FOAM. Water Resources Engineering. 2024; 10.30495/wej.2024.31570.2379.
[9] Hassanzadeh Y. Kardan N. Rushdi M. and Kamasi M. Numerical investigation of the effect of changes in geometric and hydraulic parameters of the reservoir and sediments on the rate of hydraulic sediment removal under pressure of reservoirs of reservoir dams. Journal of Civil and Environmental Engineering. 2024;54(115): 53-71. doi: 10.22034/ceej.2023.51982.2154
[10] Khorshidi H. and Nikseresht A. Investigation of the aeration system in the lower spillway of Sefidrood Dam using the finite volume method. 7th Iranian Hydraulic Conference. 2008.
[11] Banisoltan S. and Pirzadeh B. Numerical modeling of the remedial option of the lower discharge gate of Shahid Abbaspour Dam using FLUENT software. 2010. Fifth National Civil Engineering Congress, May 2010. Ferdowsi University of Mashhad.
[12] Huang H.Y. Gong A.M. Qiu Y. Wangliang Z.A. 3D Numerical Simulation and Experimental Analysis of Spillway Tunnel. Applied Mechanics and Materials. 2015; 723: 171-175.
[13] Shilpakar R. Hua Z. Manandhar B. Shrestha N. Zafar M.R. Iqbal T. Hussain Z. Numerical simulation on tunnel spillway of Jingping-I hydropower project with four aerators. IOP Conference Series Earth and Environmental Science. 2017; 82(1):012013.
[14] Rong Y. Zhang T. Peng L. Feng P. Three-Dimensional Numerical Simulation of Dam Discharge and Flood Routing in Wudu Reservoir. Water. 2019; 11(10): 2157.
[15] Shi H. Huang Y.  Feng D. Numerical investigation on the role of check dams with bottom outlets in debris flow mobility by 2D SPH. Sci Rep 12, 20456 .2022. https://doi.org/10.1038/s41598-022-24962-4.
[16] Falvey H.T. Cavitation in Ccutes and spillways. Engineering Monograph 42, US Bureau of Reclamation, Denver, Colorado. 1990; 145P.

  • Receive Date 20 November 2025
  • Revise Date 05 December 2025
  • Accept Date 17 December 2025