Experimental Study of the Scour Depth at Downstream Weirs Has Different Holes
Al-Rafidain Engineering Journal (AREJ),
2019, Volume 24, Issue 1, Pages 18-23
AbstractAn experimental study was carried out to deal with using a weir with circular holes to control the scour occurs behind it. The holes are located near the bed of the channel, their geometric details had been changed in its size, number and their distance from the bed of the channel. The channel bed was lined by crushed gravel with average diameter 11.1 cm. The thickness of the crushed gravel layer was 22 cm and its length was 4 m. There is 18 cases were conducted. Which the diameter of the holes were 1.6, 2.3, 3 cm, and for each size of them, the distance of the holes was 0, 0.25 or 0.5 cm, their number was one or three. These cases were compared with the case of using weir with no hole. The main hydraulic variable was the discharge, which five different discharges were flowed for each case. The total number of the experiments was 95. The dimensions of the scour hole behind the weir was measured as well as the water surface elevation in the upstream of the weir.
The analysis indicated that the discharge plays the main role to increase the size of the scour hole. Using the weir with holes helps to decrease the scour occurs behind it, because the flow from holes interrupted the flow fallen from over the weir then some of its energy was dissipated. The diameter of the weir's hole that caused the smallest scour was 0.115 cm, while the most effective distance of the this hole to cause the same effect was 0.5 cm, among all the studied cases. Due to its height increases the dissipation of the energy of the falling flow.
1- Dehghani, A. A., Bashiri, H., &Dehghani, N. (2010). Downstream scour of combined flow over weirs and below gates. River Flow–Dittrich, Koll, Aberle&Geisenhainer (eds).
2- Hamed, Y. A., El-Kiki, M. H., &Mirdan, A. M. (2009, March). Scour downstream oblique V-notch weir. In Thirteenth International Water Technology Conference, IWTC (Vol. 13, pp. 853-872).
3- MoayadS.andAkramKh.,(2015).”Laboratory Study For Estimating The Removing Sediment From Upstream Weirs Using Bottom Outlets”. Al-Rafidain Engineering (Vol.23,No.1,pp. 62-72).
4- NeveenY.Saad and EhabM.Fattouh.,(2017).”Hydraulic characteristics of flow over weirs with circular openings”.Ain shams Engineering Journal(No.8,pp.515-522).
5- Simon, D. B. and Senturk, F. (1992), “Sedimen Transport Technology” , A.K. Turner and R. L. Schuter editors, Water Resources Publication, Littleton Colorado USA.
6- Sobeih M.F,Helal,E,Y.,Nassralla,T.H.,Abdelaziz,A.A.(2012). “Scour depth downstream weir with openings” International Journal of Civil and Structural Engineering.(Vol.13,No1,pp. 259-270). Pagliara, S. and Palermo, M.,(2013) “Rock Grade Control Structures and Steeped Gabion Weirs Scour Analysis and Flow Features.”ActaGeophysica, Vol .61,No.pp.126-150.
- Article View: 104
- PDF Download: 194