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

Amir Ghaderi,Silvia Di Francesco,Mehdi Dasineh,Rasoul Daneshfaraz

doi:10.3390/w12071992

Amir Ghaderi, Silvia Di Francesco + Show 2 more

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https://doi.org/10.3390/w12071992

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Abstract

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.

Highlights

Weirs are extensively used for passage flood, flow measurement and deviation, and control of water level river sand open channels [1]
Since the volume of the passing flow through the weir is dependent on the length and shape of the weir crest, most research has been devoted to the influence of hydraulic and geometrical parameters on the flow discharge coefficient and the overflow discharge through weirs
The results showed that Computational Fluid Dynamics (CFD) models are able to provide very good evaluations of the discharge on free and submerged labyrinth weirs for a large sidewall angle

Summary

Introduction

Weirs are extensively used for passage flood, flow measurement and deviation, and control of water level river sand open channels [1]. Weir length at a certain width can be modified, adopting non-linear weirs, such as triangular, trapezoidal, and circular called labyrinth weirs. They are usually made in one or several cycles. The first serious investigations into the labyrinth weirs were conducted by Taylor [7] and Hay and Taylor [8]; they used the ratio of the discharges of a labyrinth and linear weirs to show the performance of the labyrinth weirs, presenting design curves with an effective head on the weir coincident with the flow depth. Kumar et al [9] experimentally investigated the labyrinth weir discharge coefficient with the triangular plan, showing that by decreasing the apex weir angle, the length of the interference zone

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