An Experimental Study of Flow over Rectangular Broad Crested Weir

Document Type : Original Article


Civil Engineering Department, Canadian International Colleague (CIC), Giza, Egypt


The main objective of this study was to investigate the flow behavior of the broad crested weir (BCW) and establish a new formula describing the discharge coefficient. In the present work, an experimental study has been carried out on twenty-five BCW physical models with various geometrical configurations and surface roughness conditions too.
Accordingly, the analysis highlights that discharge coefficient (Cd) values are directly proportional to the total head (H) acting on the broad crested weir for a fixed value of weir length (Lw) and increase with the decrease of weir surface roughness. The results showed (H/Lw) is the most studied effective BCW dimensionless ratio that significantly influences the discharge coefficient. An increasing H/Lw from 0.15 to 0.35 leads to noted discharge coefficient values increasing up to 28.39%. As consequence, a new formula with a more compact and short form of expression has been developed for the BCW discharge coefficient prediction. Moreover, a reasonable agreement was noticed between the present study results and the previous research-developed models with errors of less than 10%. Considering the proposed discharge coefficient formula, the optimum hydraulic design of the new BCW model can be successfully facilitated by the extrapolation of characteristics of the idealized scale.


Volume 46, Issue 1
issued on 1/1/2023 in 5 Parts: Part (1) Electrical Engineering, Part (2) Mechanical Engineering, Part (3): Production Engineering, Part (4): Civil Engineering, Part (5) Architectural Engineering,
January 2023
Pages 153-158