An Experimental Investigation of the Coefficient of Discharge for Circular and Semi-Circular Weirs

Nawzad O.A.Rahim1, Mahmoud I. Mahmoud1, & Haveen M. Rashid1

1College of Engineering, University of Sulaimani

The hydraulic characteristics of ciroular and semi-circular weirs under free flow and submerged flow
conditions were studied experimentally and compared. Eighteen different weir models were tested. The first
nine models were circular weirs, the rest of the models were semi-circuiar weirs. Within the range of the
experiments it is shown that the weir height (p), upstrearn head over the weir(hr) . submergence ratio(h2lh1)
and channel slope had significani effect on the coefficient of discharge (Cj. The results confirmed that the
coefficient of discharge for circular weirs was greater that semi-circular r.veirs under free flow and submerged
flow conditions, also tire va!.ue of (Co) for subrnerged flnw for both circulal and serni-cirsular weirs was l,i:rver
than that at free flow condition bV(1-15)%.

Key Words : weir, coefficient of discharge, circular, semi-circular, free flow, submerged flow, channel


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