Investigation of the efficiency of labyrinth rectangular weirs with equal and unequal congresses in the plan

The main purpose of the Labyrinth Spillway is to increase the length of the Spillway crest by nonlinearzing its shape in the plan so that is increase the efficiency and discharge coefficient. In Spillways, the overlap of the falling flows and the resulting compression of the flow during the Spillway reduces the efficiency and discharge coefficient of the Spillway. In this study, in order to reduce the interference of falling flows, the congressional Spillways with the length of unequal congresses have been studied and compared.

In this study, the congressional Spillways with the length of unequal congresses in two cases A and B in laboratory and in 5 cycles with effective length and same height which are 336 and 10 cm, respectively in the channel of the hydraulic laboratory of Bu Ali Sina University with a length of 14 meters and a width and height of 60 centimeters have been studied and compared. To conduct this research, 10 laboratory models of Labyrinth weirs with different congress lengths and one laboratory model of Labyrinth weir with the equal length of congresses have been constructed for comparison with other models. In each case, the flow rate and water depth on the Labyrinth crest were carefully monitored. This operation was repeated 3 times for each case to minimize the errors caused by the test. From the average data of each case was used for analysis and conclusion.

The results of this study show that in all congressional Spillways with unequal congress lengths, the changes of C vs. Ht / P are decreasing and with increasing the Ht / P ratio, the value of C decreases. According to the results of this study, in general, the efficiency and discharge coefficient of the Spillways of congresses of type A is better than type B.

The results show that the reduction of the impact length of falling flows up to 25% compared to the Spillways with the same length of congresses, increases the efficiency and improves the discharge coefficient and reduces the impact length of falling flows by more than 25% changes Spillway performance from the concave state and reduces the efficiency and discharge coefficient of the Spillway. Also, the best sample made in this research improved the discharge coefficient of congressional Spillways with the same length of congresses by 40.7%.