Effect of Weir Height on Flow Performance of Sharp Crested Rectangular-Planform Weir

2 Abstract: Labyrinth weirs are folded in a zigzag manner producing a longer crest length compared with a linear weir having the same lateral space to increase the discharge for a given operating head. As compared to linear weirs, labyrinth weirs have lower operating heads for a given discharge. Presented in this paper; the results of experimental investigation on twenty four different sharp crested rectangular planform weir models which are manufactured from mild steel plates to show the effect of crest height on flow performance with various crest lengths. It was found that the efficiency of the rectangular planform weirs is better than the normal weir and also high for low weir height and decreases with the increase of head over the crest of the weir due to interference of the water jets downstream. 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 weir height.