Performance of flow over a weir with sloped upstream face

Abstract EN

Measurement of flow in open channel is almost based on weirs.

A relatively smallest height of water generated upstream weirs is sometimes important issue, especially when the banks of channel are not enough.

Upstream crest slope to the crested edge of the weir reduces loss and due to that less head need to pass a discharge.

The effect of the sloped upstream face is investigated experimentally by testing four different weir heights and four slopes for each weir height.

The measured surface flow profile shows that the shape of profile curvatures are effaced by the length of upstream sloped face and then the performance of weir compared with sharp crested weir, the maximum increase in the value of discharge coefficient is 20% compared with the sharp crested weir of the same height.

The discharge coefficient decreases with increase of relative value of the head to the weir height (H/P) and increase with the value of face length to the head (L/H) and with face length to the depth of water over crest (L/h).

The water surface profiles are predicted by HEC-RAS and then compared with measured profiles.

The comparison shows a reasonable acceptance.

Dimensionless relations are suggested for each weir height to predicting the discharge coefficient with acceptable coefficient of determination R2.