A new approach to improve the discharging capacity of sharp-crested triangular plan form weirs

Conventional weirs are inherited with afflux and submergence of area upstream of the weir. Various weirs of modified plan form have been suggested in the past to enhance their discharging capacity and to restrict the afflux. Presented in this paper are results of the experimental study carried out to investigate the discharging capacity of a sharp-crested triangular plan form weir under free flow conditions in a rectangular channel. The efficiency of the triangular plan form weirs is better than the normal weir and also high for low vertex angle and decreases with the increase of ratio of head over the crest of the weir and crest height due to interference of the water jets downstream. The computed discharge using the proposed equation is within ±5% of the observed ones. Sensitivity of the weir, i.e., change of discharge due to unit change in head is also carried out which indicates that the weir is more sensitive at the low head and low vertex angle.

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► The coefficient of discharge of triangular plan form weir decreases with decrease of vertex angle and increase of ratio of head over the crest and crest height.
► The proposed equation for the computation of discharge is accurate and computes the discharge within five percent error.
► The efficiency of the triangular plan form weir is high for low vertex angle and decreases with increase of ratio of head over the crest and crest height.
► The discharge through triangular plan form weir is more sensitive to the low head and low vertex angles. As the head increases, the sensitivity decreases due to interference of the water jet downstream of the weir crest.