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

Document Type : Technical Note


Irrigation and Reclamation Engineering Department, University of Tehran


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%.