Investigation of the Experimental and Numerical Modeling of the Effect of Creating an Additional Cycle and Placement of the Nappe Breaker on the Hydraulic Performance of the Labyrinth Weir

The results of the dimensional analysis by Buckingham method showed that the discharge coefficient(Cd), function "Ht/P" (represents the total hydraulic head ratio (total hydraulic head to the height of the weir)), "Sf" (represents the form factor of the weir) and "Nnp".Physical and numerical modeling was done in a rectangular flume with the length of 8 meters, width of 0.6 meters and height of 0.6 meters.The results of the study showed that creating an additional cycle has a positive effect on the TRTPIO weir, and it causes the discharge coefficient as well as its hydraulic performance to increase compared to the placement of the nappe breaker.creating an additional cycle and placing the nappe breaker on the labyrinth weir at the same time makes the TPTPIO weir with 4 nappe breakers have a higher discharge coefficient than other models.Quantitative evaluation of the results of this study shows that, for example, in the hydraulic head ratio of 0.24, the discharge coefficient of TRTPIO weir compared to TPTPIO weir, TPTPIO with 4 nappe breakers, TRTPIO with 4 nappe breakers, is 21, 8.5 and 21% have higher discharge coefficient; On the other hand, the Mattos-Villarroel weir has a higher discharge coefficient than the TRTPIO weir by 7.8%.The results of numerical modeling showed that with the increase of hydraulic head, the discharge coefficient decreases.while the increase of hydraulic head in labyrinth weirs causes an increase in the interference of nappe flow, energy loss, local submergence, and finally, a decrease in the hydraulic efficiency of the weir.