Experimental Study of Discharge Coefficient of Trapezoidal Arced Labyrinth Weirs with Different Arc Radius and Cycle Length

Labyrinth weirs are structures for transferring large flows at low heads, in which the effective length of crest for a given channel width is increased. In this study trapezoidal arced labyrinth weirs with different arc radius and cycle length were investigated. Several experiments were conducted using physical models to evaluate the effect of R/w1 (ratio of arc radius to middle cycle width) and B/w1 (ratio of weir length in flow direction to middle cycle width) on weir discharge coefficient. The experiments were carried out using a 6 m long test flume with cross section of 0.6 m width and 0.6 m height. Using Buckingham method of dimensional analysis, it was found that the discharge coefficient is a function of three variables; hydraulic head, arc radius of weir and weir length ratio. In general, the results of this study showed by increasing arc radius ratio, discharge coefficient of trapezoidal arced labyrinth weir increases up to 27.3%. Besides, by decreasing the weir length ratio from 1.5 to 1, discharge coefficient increased up to 29.7%.