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Showing 4 results for Labyrinth Weirs
An Experimental Study of the Discharge of the Length Increase Effect on the Composite Trapezoidal Labyrinth Spillway
H. Azarpeyvand, A. R. Emadi, M. Sedghi Asl,
Volume 23, Issue 1 (6-2019)
Abstract
Labyrinth weirs are the economic structures to increase the weir output efficiency in limited widths, which can be seen in the plane f trapezoidal and triangular forms. These weirs with a hydraulic load and fixed width pass the more discharge in comparison to other type of weirs. In this study, labyrinth weirs trapezoidal in plane form were investigated. The experiments were performed on 27 laboratory models with 9 different discharge rates and a total of 243 tests. The results showed that, in all of the composite trapezoidal labyrinth weirs, the ratio of discharge coefficient to Ht/p (Ht: Total hydraulic load and p: weir length) weir length was increased at first; after reaching the maximum rate, it started to decrease. According to the suggested general relation, the utmost impact on discharge coefficient resulted from the cycle number and  Ht/p relation. Creating new labyrinth on the wing of the weir led to the increase of the effective length; as a result of it, the discharge rate increased in a specific amount of Ht/p. Also, the discharge through a trapezoidal labyrinth weir with the semicircular planform was better than the square; the square, in turn, was better than the simple trapezoidal weirs.

Numerical Analysis of Flow Hydraulic in Trapezoidal Labyrinths and Piano Key Weirs
R. Gharibvand, M. Heidarnejad, H. A. Kashkouli, H. Hasoonizadeh, A. Kmanbedast,
Volume 24, Issue 1 (5-2020)
Abstract
The flow fields over a trapezoidal labyrinth weir (two-cycle) and a piano key weir were simulated using Flow3D, studying the impact of each model on the flow field in the weirs and the coefficient of discharge in comparison with the available experimental data. Moreover, the models were investigated experimentally in a 12.5 m long, 0.3 m wide, and 0.4 m high rectangular flume under clear-water conditions. The results showed good agreement between the data from the numerical and experimental models. The piano key weirs had a higher coefficient of discharged compared with labyrinth weirs. The coefficient of discharge was observed to increase by 26 percent as the height of the PKW was increased by 50 percent (from 5 to 7.5 cm). This increase was 24 percent for labyrinth weirs.

Experimental Study of Discharge Coefficient of Symmetric and Asymmetric Rectangular Labyrinth Weirs
H. Elahifar, O. Tayari, N. Yazdanpanah, M. Momeni,
Volume 25, Issue 4 (3-2022)
Abstract
The discharge coefficient of labyrinth weirs increases with increasing the crest length in a certain width range. The present research was carried out in a laboratory flume with a length of 8 m, a width of 0.6 m, and a height of 0.6 m. The discharge coefficient of two-cycle symmetric and asymmetric rectangular labyrinth weirs was experimentally measured. The dimensional analysis by the Buckingham π theorem indicated that the discharge coefficient was dependent on Se, B/Wavg, Ht/P, and WL/WR. According to the results, the discharge coefficient decreased with increasing the hydraulic head in the symmetric and asymmetric labyrinth weirs and the linear weir. Asymmetric labyrinth weirs with a WL/WR of 2.05 outperformed symmetric labyrinth weirs with a WL/WR of 1. Quantitatively, the discharge coefficient of the labyrinth weir with a B/Wavg of 3.1 was respectively 21% and 94% higher than that with a B/Wavg of 2.93 and 2.76. The discharge coefficient of the labyrinth weir with a WL/WR of 2.05 was 10-27% higher than that with a WL/WR of 1. The discharge coefficient of the linear weir was 60-250% higher than that of labyrinth weirs.

Laboratory Investigation of the Effect of Wall Slope on the Discharge Coefficient of Trapezoidal Arced Labyrinth Weirs
M. Majedi Asl, T. Omidpour Alavian3, M. Kouhdaragh,
Volume 27, Issue 4 (12-2023)
Abstract
Weirs of the labyrinth have some advantages including the high coefficient of the irrigation of weir and the low fluctuation of water when the flow passes over the crest of the weir. In this research, the flow rate coefficient has been investigated by changing the weir geometry in terms of wall slope, arc cycle angle, and nose length change in the upstream and downstream of each cycle of the trapezoidal arc labyrinth weir. A total of 240 tests have been performed on 16 different physical models in a channel with a width of 120 cm and a narrowing of 20 cm from each wall. All models have been compared with the control model (normal labyrinth weir) (80A). The results showed that the 80B weir with an arc cycle angle of 20 degrees and without wall slope has a better performance than other weirs. Also, the weir with an arc cycle angle and a wall slope of 20 degrees in a divergent form (D20B) in the area (Ht/P) <0.31 has a better performance than other weirs with an arc cycle angle of 20 degrees, and after this area, the weir with a wall slope of 10 degrees has performed better in divergent form (D10B). In weirs with different cycles at an arc cycle angle of 20 degrees, the labyrinth weir with 5 cycles (N5) has performed better up to the point (Ht/P)=0.36. Also, at the maximum point, the difference is 13 and 17%, respectively, compared to the 4-cycle and 3-cycle weirs.

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