A comprehensive experimental investigation on discharge formulae of free flow over fully contracted rectangular sharp-crested weirs

In this study, laboratory experiments were conducted to investigate the discharge characteristics of free flow over rectangular sharp-crested weirs under the situation of large discharges and high water heads. By adding the weir plates with contraction ratios which were not considered in the literature, a new division for the rectangular sharp-crested weirs was proposed. The performances of the available discharge coefficient equations from the literature were evaluated and improved. It was found that the water head has significant effect on the accuracy of the proposed discharge coefficient equations. The discharge coefficient is suitable to be described by the Reynolds number at low heads and the contraction ratio at high heads, this is determined by the flow characteristics of the rectangular sharp-crested weir. The work presented in this paper would be useful to enrich and develop the research on the flow discharge of rectangular sharp-crested weirs.