Developing Practical Relationships for Circular Sharp Crested Weirs Based on Hydraulic Sensitivity Concept

Weirs are the most common hydraulic structures for discharge measurement. Variety of weir types have been developed and used so far. Sharp crested circular weirs provide specific advantages and could be employed in different circumstances. However, the complex discharge relationship of these weirs limits their applications. In this study the currently available complex relationships of sharp crested circular weirs have been investigated and based on the hydraulic sensitivity concept, simple yet practical and reliable discharge evaluation relationships were proposed accordingly. It was shown that the relative sensitivity of circular weir is restricted to 1.2 to 2 which is lower than that of triangular weir, whereas it might be higher or lower than the sensitivity of rectangular weirs based on the range of non dimensional head value. The validity of the proposed relationships was examined according to the available experimental data which showed that for a very wide range of the employed data the discharge could be evaluated with a marginal error of less than 2.5%.