Experimental study of the effect of wall slope on the discharge coefficient of labyrinth weirs

The advantages of labyrinth weirs include high discharge coeficient and low water fluctuations, when flowing through the weir. The main objective of the present study is to experimentally investigate the variations of labyrinth weirs discharge coefficient (Cd) through altering the geometric parameters as the wall slope and the length of upstream and downstream apexes of each cycle. A total of 135 experiments were performed on 9 physical models in contracted canal (20 cm on each side). All models have been compared with the control sample (normal labyrinth weir,80A). The results showed that the trapezoidal labyrinth weir with an upstream apex of 5 cm with a wall slope of 10 degrees in the state of convergence (U10A) has a higher discharge coefficient and efficiency than the model without a wall slope. Their maximum difference is more than 12%. Also, the trapozidal labyrinth weir with an upstream apex of 8 cm with a wall slope of 10 degrees in the state of divergence (D10A) at the ratio of ht/p lower than 0.37, has a higher performance than the 80A model. By increasing this ratio and discharge, its superiority decreases. Finally, the results showed that by changing the slope of the walls by 10 degrees, the performance of the trapezoidal labyrinth weir increases compared to the non-sloping walls (verticall walls).