Unsteady Flow in V-Notch Weir Located at the End of a Storage

Sharp-crested weirs are common measuring devices in rivers and irrigation networks. Their installation and operation are simple yet very practical. The hydraulic performance of sharp-crested weirs and their head-discharge equations in unsteady flow condition are of great interest, however, very limited studies are available in the literature. In the present study, the hydraulic performance of 90° V-notch weir, located at the end of a storage, was investigated in unsteady flow condition and the differences between steady and unsteady overflow were observed and evaluated. The results indicate that the difference between steady and unsteady discharges are significant whereas the difference value of investigated scenarios arise up to 40 percent, sometimes. Therefore, the previous head-discharge equations are no longer valid.