The dimensions of many water streams, which satisfy proper hydraulic conditions, may not be compatible with the designed dimensions of an irrigation work that needs to be constructed in some locations. The design requirements of such irrigation works may involve a contraction in the channel width in the required location. This contraction, of course, affects different flow properties and the scour hole formed downstream of these structures. Therefore, the present experimental study aims to investigate the effect of the transition angle and the contraction on the flow properties and on the scour phenomenon downstream water structures. Through 460 experimental runs, carried out on 20 experimental models, the study proved that, for an efficient hydraulic performance and economic design, the best transition angle (θ) for the approaches of water structures is 30° with a relative contracted width ratio (r = b/B) not less than 0.6.
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Alsamman O.M. 1989 Flow characteristics in channel with local contractions [Thesis] King Saud University Faculty of Engineering Riyadh 98 pp.
Attia M.I. 2000 Effect of contraction ratio and transition angle on the energy loss in horizontal open channel transitions Proc. of the 5th International Water technology Conference (IWTC) 3–5 March 2000 Alexandria: 97–106.
Attia M.I. Alhomidan A. 2013 Effect of free surface and Froude number on the protection length and turbulence in the compound transitions through bridges Int. J. Res. Eng. Technol. (IJRET) 2(11): 394–411.
Devadason B.P.I. 2007 Contraction scour in compound channels with cohesive soil beds [Thesis] Texas A&M University College Station 118 pp.
Dey S. Raikar V. 2005 Scour in long contractions J. Hydraul. Eng. 131(12): 1036–1049.
Henderson F.M. 1966 Open channel flow Macmillan. New York 522 pp.
Ippen A.T. Dawson J.H. 1951 Design of channel contraction T. Am. Soc. Civ. Eng. 116: 326–346.
Mohamed Y.A. Abdel-Aal G.M. Nasr-Allah T.H. Shawky A.A. 2016 Experimental and theoretical investigations of scour at bridge abutment J. King Saud Univ. Eng. Sci. 28: 32–40.
Negm A.M. Elfiky M.M. Attia M.I. Ezzeldin M.M. 2003 Protection length downstream of sudden transition for incoming sub critical flow Proc. of the 1st International Conference of Civil Engineering Science (ICCES1) Vol. 1 October 2003 Assiut 9 pp.
Wu B. Molinas A. 2005 Energy losses and threshold conditions for choking in channel contractions J. Hydraul. Res. 43(2) 139–148.
Xiong X. Melville B.W. Friedrich H. 2013 Effects of contraction length on abutment scour Proc. of the 35th IAHR Congress 8–13 September 2013 Chengdu 10 pp.
Zidan A.R. Owais T.M. Rashwan I.M. 1990 Horizontal transitions in subcritical flow Mansoura Eng. J. (MEJ) 15(1): 221–242.
Zidan A.R. El-Gamal M.A. Abdallah M.G. Mohamed M.H. 2015 Compound transitions in open channels [Thesis] Mansoura University Faculty of Engineering Mansoura.