Discharge Characteristics of Rectangular Thin-Plate Weirs

A comprehensive solution is proposed for the discharge characteristics of rectangular, thin-plate weirs. The solution is based on a simple equation of discharge and experimentally derived coefficients which account for the influence of the fluid properties and the physical characteristics of the weir and the weir channel. The effects of viscosity and surface tension are related to an increase in the effective head and an increase or decrease in the effective notch width. Thus, the combined effects of the fluid properties are accounted for with adjustment coefficients which are applied to measured values of the head and width. Consequently, the coefficient of discharge is defined as a function of geometric ratios which describe the weir and the weir channel. Values of the coefficients required to describe the discharge of water over rectangular, thin-plate weirs are determined from original tests covering a wide range of the significant ratios. Additional data needed to confirm the proposed method of analysis are obtained from the published results of experiments performed by other investigators. The proposed discharge equation is compared with some of the most widely used formulas.