Hydraulics of flow over rectangular labyrinth weirs

Azimi, Amir H.; Hakim, Sara Seyed

doi:10.1007/s00271-018-0616-6

Cited by 28 publications

(19 citation statements)

References 22 publications

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“…The performance of pool‐weir fishways can be also improved by increasing the crest length of the weirs (Baki, Zhu, et al, , ; Kupferschmidt & Zhu, ). One way of increasing the length of a weir is by folding the crest length in plane view to form rectangular or triangular labyrinth weirs (Azimi, ; Azimi & Hakim, ). In addition, effect of channel slope on the water surface profile can be correlated with the tailwater depth (Azimi, Rajaratnam, & Zhu, ).…”

Section: Introductionmentioning

confidence: 99%

Hydraulic and turbulence structure of triangular labyrinth weir‐pool fishways

Dizabadi

Azimi

2019

River Research & Apps

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Detailed laboratory experiments were conducted to analyze and evaluate a new weir-pool fishway design. The new design consisted of a series of one-cycle, triangular labyrinth weirs that formed a weir-pool fish passage. Hydraulic characteristics of flow over the proposed fishway were examined for three pool lengths and a wide range of discharges. It was found that the new design had superior discharge capacity over classical weir-pool fishways in plunging flow regime. Spatial and point analyses of measured velocity data were carried out to understand turbulence structure and distribution of turbulent flow. The power dissipation per unit volume was calculated for different tests, and it varied nonlinearly with discharge. Based on the limiting criteria for energy dissipation rates of different fish species, the maximum operating discharge for different slopes was extracted for the proposed design. The model-toprototype scaling analysis was performed based on the recommended scaling factor of three for prototype. It was found that the approach velocity of prototype increased by 12%, whereas the total discharge increased by more than five times.The contour plots of time-averaged velocity indicated that the proposed fishways offered diversified flow fields without exceeding the maximum velocity above the standards recommended for weir-pool fishways. To study the size, direction, and periodicity of turbulent eddies, magnitude of the most energetic eddy and dominant frequencies were extracted using power spectrum analysis. Quadrant analysis consistently showed that Reynolds shear stresses in ejection and sweep events became weaker as the pool length increased. The small region of strong ejection and sweep events evidenced a good resting place for fish migration, whereas the generated turbulence was large enough to attract fish species to use the passage. K E Y W O R D S energy dissipation, fishway, pool and weir fishway, power spectrum, quadrant analysis, Reynolds shear stress, turbulence

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Section: Introductionmentioning

confidence: 99%

Hydraulic and turbulence structure of triangular labyrinth weir‐pool fishways

Dizabadi

Azimi

2019

River Research & Apps

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“…Their results showed that by increasing the angle of the weir apex, the crossflow interference with the lateral fall blades reduced and created less flow vortex. Azimi and Hakim [14] experimentally studied hydraulic passing flow through a rectangular labyrinth weir, demonstrating its suitability for the ratio h 0 /P < 0.4 (h 0 the flow head over the weir and P weir height). Also, under submerged conditions, a rectangular labyrinth weir is more sensitive to the linear weir, and its efficiency is reduced by 10% over the linear weir.…”

Section: Introductionmentioning

confidence: 99%

Energy Dissipation and Hydraulics of Flow over Trapezoidal–Triangular Labyrinth Weirs

Ghaderi

Daneshfaraz

Dasineh

et al. 2020

Water

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In this work experimental and numerical investigations were carried out to study the influence of the geometric parameters of trapezoidal–triangular labyrinth weirs (TTLW) on the discharge coefficient, energy dissipation, and downstream flow regime, considering two different orientations in labyrinth weir position respective to the reservoir discharge channel. To simulate the free flow surface, the volume of fluid (VOF) method, and the Renormalization Group (RNG) k-ε model turbulence were adopted in the FLOW-3D software. The flow over the labyrinth weir (in both orientations) is simulated as a steady-state flow, and the discharge coefficient is validated with experimental data. The results highlighted that the numerical model shows proper coordination with experimental results and also the discharge coefficient decreases by decreasing the sidewall angle due to the collision of the falling jets for the high value of H/P (H: the hydraulic head, P: the weir height). Hydraulics of flow over TTLW has free flow conditions in low discharge and submerged flow conditions in high discharge. TTLW approximately dissipates the maximum amount of energy due to the collision of nappes in the upstream apexes and to the circulating flow in the pool generated behind the nappes; moreover, an increase in sidewall angle and weir height leads to reduced energy. The energy dissipation of TTLW is largest compared to vertical drop and has the least possible value of residual energy as flow increases.

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“…It is typically constructed by placing linear weirs in a zigzag pattern, folded in the plan view. Therefore, since it is usually constituted by repeated in plan-view simple shapes (cycles), such as U-shape (halfcircular shape), circle-shape (sinusoidal shape), V-shape (triangular shape), rectangle (rectangular shape), and trapezoid (trapezoidal shape) shapes, both the design and construction of labyrinth weirs are very cost-effective [2,5,10,11].…”

Section: Introductionmentioning

confidence: 99%

“…One of the labyrinth weir types that has excellent structural and economical characteristics is the rectangular labyrinth weir [10,16]. The rectangular labyrinth weir is a labyrinth weir that has a right angle (90 degrees) between two adjacent weir sides; the weir tips (apexes) are perpendicular to the sidewalls [7], see Figure 1.…”

Section: Introductionmentioning

confidence: 99%

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Effect of Corner Shape on Hydraulic Performance of One-Cycle Rectangular Labyrinth Weirs

Yousif

Karakouzian

2020

Fluids

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The hydraulic performance of rectangular labyrinth weirs has been investigated by many researchers, however, the effects of the corner shape on the hydraulic performance of rectangular labyrinth weirs have not been addressed in the current literature. Accordingly, this experimental study aims to explore the effect of the corner shape of on discharge efficiency of rectangular labyrinth weirs. Five flat-crested rectangular labyrinth weirs, with five different corner shapes, were made of High-Density Polyethylene Plastic (HDPE) and tested in a rectangular flume. Under different overflow discharges, the discharge coefficients for the rectangular labyrinth weirs were determined. The results showed that the shape of corners for rectangular labyrinth weirs was an effective factor. For example, rounding or beveling the corners can significantly increase the discharge capacity of the rectangular labyrinth weirs. However, the rounded corner shape was slightly better than the beveled corner shape. Among all labyrinth weir models tested in this study, the rectangular labyrinth weir with a semi-circular apex showed the highest hydraulic efficiency, while the one with an acute-angle corner shape showed the lowest hydraulic efficiency. For the rectangular labyrinth weir having a semi-circular shape, although the original effective length reduced by about 14%, the discharge coefficient, CL, increased by 16.7% on average. For the rectangular labyrinth weir that has an acute-angle corner shape, although the effective length (LC) of the weir increased by 23%, its discharge capacity decreased by 35.2% on average. Accordingly, improper folding of the side-walls of the rectangular labyrinth weir led to a significant reduction in the weir’s hydraulic performance.

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Hydraulics of flow over rectangular labyrinth weirs

Cited by 28 publications

References 22 publications

Hydraulic and turbulence structure of triangular labyrinth weir‐pool fishways

Hydraulic and turbulence structure of triangular labyrinth weir‐pool fishways

Energy Dissipation and Hydraulics of Flow over Trapezoidal–Triangular Labyrinth Weirs

Effect of Corner Shape on Hydraulic Performance of One-Cycle Rectangular Labyrinth Weirs

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