The Role of chute Blocks Geometry in Current Erosion Power Loss

Document Type : پژوهشی

Authors

• sobhan moradi ¹
• hamed shahsavari ¹
• kazem esmaili ²

¹ Department of Water Engineering, Ferdowsi University of Mashhad, Iran.

² Associate Professor at Department of Water Engineering, Ferdowsi university of Mashhad. Iran.

10.22067/civil.v33i3.86241

Abstract

The high energy impinging on the outflow through the overflows is controlled by the design of the energy absorber structures in the downstream or downstream relaxation pool. However, the occurrence of downstream local scour is one of the major threats to the stability of the overflows. In the present laboratory research, first, by conducting control experiments (unimpeded shot) at different landing numbers, the geometry of the scour pit was investigated, then by providing a basic block-height protection method in three geometric shapes (Rectangular, Semicircular, Triangle), four mounting positions proportional to the total L_b/L_f shot length (0.2, 0.4, 0.6, 0.8) and also, to concave the installation of blocks, the dimensions of the scour pit are measured and Dimensional analysis was performed using Pie-Buckingham method. The results showed; The use of block base on the slope of the shot in all the models tested has an effect on the dimensionality of the scour and has always reduced the dimensions of the scour pit. In summary: 1. The depth and final length of the scour increases with the increase in the number of upstream landing overflows. 2. In the series of upward concave tests, blocks always have lower values ​​of scour dimension than low facing concave. 3. By decreasing the installation distance of the blocks from the overflow claw, the scour depth and length decrease. So that at position (Lb/Lf = 0.8) the highest energy damping occurred at other positions. And under different conditions the flow decreases between 15 to 61.2% of the depth of the scour pit. 4. In position (Lb/Lf = 0.6), semicircular and rectangular blocks with low upward concavity and also in position (Lb/Lf = 0.8) triangular block with high upward concavity, with average yield 38/1 to 73/4% had the highest decrease during scour compared to other states. 5. By increasing the number of downstream currents, the relative damping energy of the current in the shoot paw decreases.

Keywords

• Block Geometry
• Scour hole
• Barrier Pattern
• Energy
• Depreciation

---

References

1. Dargahi, B., "Scour Development Downstream of a Spillway", Journal of hydraulic research, Vol. 41, No. 4, Pp. 417-426, (2003).
2. Abdelhaleem, F. S. F., "Effect of Semi-circular Baffle Blocks on Local Scour Downstream Clear-overfall Weirs", Ain Shams Engineering Journal, Vol. 4, No. 4, Pp. 675-684, (2013).
3. Helal, E. Y., Nassralla, T. H., and Abdelaziz, A. A., "Minimizing of Scour Downstream Hydraulic Structures Using Sills", International Journal of Civil and Structural Engineering, Vol. 3, No. 3, Pp. 591, (2013).
4. Helal, E. Y., "Minimizing Scour Downstream of Hydraulic Structures Using Single Line of Floor water jets", Ain Shams Engineering Journal, Vol. 5, No. 5, Pp. 17-28, (2013).
5. Hong, S., Biering, C., Sturm, T. W., Yoon, K. S., and Gonzalez-Castro, J. A., "Effect of Submergence and Apron Length on Spillway Scour: Case Study", Water, Vol. 7, No. 10, Pp. 5378-5395, (2015).
6. Blaisdell, F. W., "Development and Hydraulic Design, Saint Anthony Falls stilling Basin", Transactions of the American Society of Civil Engineers, Vol. 113, No. 1, Pp. 483-520, (1948).
7. Tuna, M. C., "Effect of Offtake Channel Base Angle of Stepped Spillway on Scour Hole", Pp. 239-251, (2012).
8. Peterka, E. S., and Karon. I. M., "Congenital Pseudoainhum of the Fingers: Report of a Case", Archives of dermatology, Vol. 90, No. 1, Pp. 12-14, (1964).
9. Chatila, J. G., and Bassam R. J., "Stepped spillway as an energy dissipater", Canadian Water Resources Journal/Revue canadienne des ressources hydriques, Vol. 29, No. 3, pp. 147-158, (2004).
10. Young, M. F., "Feasibility Study of a Stepped Spillway", In Applying research to hydraulic practice, Pp. 96-105. ASCE, (1982).
11. Mohammed, T. A., Noor, M. M. M., Huat, B. K., Ghazali, A. H., and Yunis, T. S., "Effect of Curvature and End Sill Angle on Local Scouring at Downstream of a Spillway." International Journal of Engineering and Technology, Vol. 1, No. 1, Pp. 96-101, (2004).
12. Dwemawan, V., and Legono, D., "Residual Energy and Relative Energy Loss on Stepped Spillway", Journal of Applied Technology in Environmental Sanitation, Vol. 1, No. 4, (2011).
13. Chafi, C., Hazzab, A., and Seddini, A., "Study of Flow and Energy Dissipation in Stepped Spillways", Jordan Journal of civil engineering, Vol. 4, No. 1, Pp. 1-11, (2010).
14. Zare, H. K., and Doering, J. C., "Energy Dissipation and Flow Characteristics of Baffles and Sills on Stepped Spillways", Journal of hydraulic research, Vol. 50, No. 2, Pp. 192-199, (2012).
15. Kaya, N., and Emiroglu, M. E., "Study of Oxygen Transfer Efficiency at Baffled Chutes." In Proceedings of the Institution of Civil Engineers-Water Management, Vol. 163, No. 9, Pp. 447-456. Thomas Telford Ltd, (2010).
16. karimi Chahartaghi, M., and Solimani B. M., "Effect of Block Geometry and Divergence of Baffled Chute on Downstream Scour Pattern", (2019).
17. Raudkivi, A. J., and Ettema, R., "Clear-water Scour at Cylindrical Piers", Journal of Hydraulic Engineering, Vol. 109, No. 3, Pp. 338-350, (1983).
18. Kummar, V., Ranga Raju, K. G., and Vittal, N., "Reduction of Local Scour Around Bridge Piers Using Slot and Collar", Journal of Hydraulic Engineering, ASCE, Vol. 125, No. 12,pp. 1302–1305, (1999).
19. Zolghadr, M., "Effect of Six-Legged Elements Installation Arrangement on Bed Topography Around Wing-Wall Abutments", Pp. 47-57, (2018).

20. Chahardahcheriki, gholi zadeh. P., and Shafai-Bajestan, M., "Scour Dimensions of the Downstream Hydraulic Jump Stilling Basin with Bed Covered with Six-Legs Elements", Irrigation and Drainage Structures Engineering Research, Vol. 17, No. 66, Pp. 105-118, (2016). (In Persian)

21. Aydin, M. C., and Ulu, A. E., "Effects of Different Shaped Baffle Blocks on the Energy Dissipation and the Downstream Scour of a Regulator", Journal of Science and Technolog, Vol. 8, No. 2, Pp. 69–74, (2018).

22.Elnikhely, E. A., "Investigation and Analysis of Scour Downstream of a Spillway", Ain Shams Engineering Journal, Vol. 9, No. 4, Pp. 2275-2282, (2018).