Experimental study for measuring discharge through compound broad crested weir

This paper deals with a new compound broad crested weir for measurement of discharge. Calibration of broad crested weir is mainly dependent upon the length of the weir crest (L), weir height and upstream water head over weir crest (h). Hence measurement of discharge varies as per change in the flow characteristics due to change in the geometry of weir for a given flume. Based on experimental analysis, past researchers have shown that discharge coefficient (C-d) changes proportionally with h/L ratio, maintaining an average range of C-d for various h/L values. In the present study a novel approach towards design of compound broad crested weir is proposed which can effectively measure wide range of discharges thereby maintaining a constant discharge coefficient irrespective of the head over weir. Experimentation has been carried out in a laboratory horizontal tilting flume 2.5 m long, 20 cm wide and 30 cm deep. The investigation is carried out for discharge ranging from 10 lps to 2 lps. In the earlier experimentation conducted C d was varying in the range from 0.518 to 0.648, after which the broad crested weir model is modified for suiting best results thereby resulting in the reformed discharge coefficient values of 0.546-0.599 which is in close proximity to the design input value of 0.6.