SLOPE EFFECT ON DISCHARGE EFFICIENCY IN RECTANGULAR BROAD CRESTED WEIR WITH SLOPED UPSTREAM FACE

The rectangular broad crested weirs are widely used to measure the water discharge which is one of the most popular tools in the irrigation canals particularly, in developing countries. the present article is trying to demonstrate the results of an experimental work carried out on rectangular broad crested weir with sloped upstream face to investigate the effect of upstream slope on discharge efficiency. the upstream slope was varying from 90 to 23 degrees while incoming discharge was ranging from 14 to 75 lit/ sec. the experiments were conducted in a flume with a weir of fixed height under the normal downstream water depth .it is revealed that the slope of upstream face in rectangular broad crested weir would smoothen the flow profile having the critical depth on the weir crest adjacent and upstream of downstream edge of the weir . the results also lead to a novel achievement showing that the weir discharge efficiency is dependent on the slope of upstream face of the weir. as the slope of upstream face of the rectangular broad crested weir is decreasing from 90 to 23 the weir discharge efficiency is increasing and reaching to its maximum through a parabola function at slope angle of 25 degrees(i.e. 1:2.15). the investigation also showed that the depth of flow over the weir crest, the specific energy head of the approaching flow relative to chanel bed and the critical depth would be a pertinent similarity scales to asses the flow behavior over different sloped rectangular broad crested weirs between model and prototype. however, some broad investigation is recommended to endorse the achievements.