Authors : Sina Tarighi; Parisa Ghasemzadeh; Behnam Jabbari kalkhoran

Volume/Issue : Volume 9 - 2024, Issue 5 - May

Google Scholar : https://tinyurl.com/bdehfhjp

Scribd : https://tinyurl.com/4me2pxsj

DOI : https://doi.org/10.38124/ijisrt/IJISRT24MAY2113

Abstract : It is evident that water resources are essential for the existence of living organisms, particularly human life. Outlets are a series of structures employed to transfer water from the dam reservoir to the discharge point downstream. Due to the significance of this section of the dam, the performance analysis of the outlet, including the channel, gates, and their outlet, is sensitive. The presence of pressurized flow in the upstream of the outlet gate, energy dissipation due to various factors, and the very low values concerning the gate opening compared to the water head over the outlet gate cause significant errors in determining various parameters related to the outlets. This includes pressure drops across the gates and their discharge capacities when using theoretical methods. This research aims to investigate pressure distribution at various points along the outlet channel, determine the gate discharge capacity, and calculate its discharge coefficient. It explores the possibility of cavitation occurrence, compares the presented scenarios for post-service and emergency gate operations in the simultaneous operation of two gates, and determines the main loss coefficients in the channel, including frictional losses, conversion losses, and gate losses. This investigation utilizes data obtained from the physical model of the spillway outlet constructed at the Soil and Watershed Conservation Research Center laboratory. The physical model includes the channel and gates (service and emergency), and necessary experiments were conducted. The pressure values at different points, gate discharge rates at three opening levels (60%, 80%, and 100%), were measured in the reservoir, and the results are presented in corresponding tables and graphs. Additionally, the Flow 3D software was employed to numerically model the outlet discharge under three gate openings (60%, 80%, and 100%) for comparison between experimental and numerical results and with previous findings in this research. Subsequently, it will be demonstrated that, under single-gate operation and simultaneous operation, the cavitation index in critical areas, such as gate slots and between gates, in the single- gate mode falls within an acceptable range, practically eliminating the risk of cavitation. However, in simultaneous operation mode, negative pressures occur in some gate openings, posing the possibility of cavitation occurrence.

Keywords : Cavitation, Gate Slot, Hydraulic Structures, Physical Model.

References :

1. Hosseini, S. M., & Abrishami, J. (2008). "Open Channel Hydraulics: Hydraulic." 18th edition, Imam Reza University Press, Mashhad.
2. Marston, L. and Cai, X. (2016), An overview of water reallocation and the barriers to its implementation. WIREs Water, 3: 658-677. https://doi.org/10.1002/wat2.1159
3. Emamgholizadeh, S., Borojeni, H. S., & Bina, M. (2005). The Flushing of the Sediments near the Power Intakes in the Dez Reservoir. Transactions on Ecology and the Environment, 83, 621-630.
4. Emami, M. K., Kavyanpour, M. R., & Roshan, R. (2010). "Numerical Investigation of Velocity Distribution in Turbulent Flow in Submerged Discharge Outlets (Case Study: Submerged Discharge Outlet of Sefidrood Dam)." 9th Iranian Hydraulic Conference, Tarbiat Modares University, November 2009, Tehran.
5. Nezhad Nadari, et al. "Simulation of Flow in the Bottom Outlet of the Narmashir Dam." First National Conference on Dams and Hydropower Plants, 2011.
6. Nakhei, M. (1999). "Pressure Fluctuations in Downstream of Submerged Gates." Master's thesis, K.N. Toosi University of Technology, Tehran.
7. Naudascher, E., & Rockwell, D. (1994). "Flow-induced Vibration, IAHR Design Manual No.7." Balkema.
8. Jin, T. (1990). "Cavitation in Hydraulic Structures."
9. Najafi, M.R., Roshan, R., Zarrati, A.R., Kavianpour, M.R. (2009). Numerical Modeling of Flow Condition in a Bottom Outlet. In: Advances in Water Resources and Hydraulic Engineering. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-540-89465-0_313.
10. Bowers, E., & Toso, J. (1988). "Karnafuli Project, Model Studies of Spillway Damage." Journal of Hydraulic Engineering, ASCE, Vol. 114, No. 5.
11. W. T., & Dahleh, M. D. (1998). "Theory of Vibration with Applications."
12. Qasemzadeh, F. (2015). "Simulation of Hydraulic Problems in Flow-3D." Nashravaran Publications, 2015.
13. Amirsayafi, P. Measures for Success in Dam Bottom Outlet Design. GSTF J Eng Technol 3, 30 (2015). https://doi.org/10.7603/s40707-014-0030-2
14. Pearsall, I. S. (1974). Cavitation. Chartered Mechanical Engineer, 21(7).
15. J.-P. Franc and J.-M. Michel, “Attached cavitation and the boundary layer: Experimental investigation and numerical treatment,” J. Fluid Mech. 154, 63–90 (1985).
16. S. R. Gonzalez-Avila, F. Denner, and C.-D. Ohl, “The acoustic pressure generated by the cavitation bubble expansion and collapse near a rigid wall,” Phys. Fluids 33(3), 032118 (2021)