Étude théorique des grilles de prises d'eau du type « En-Dessous »

Bottom rack intake systems are one of the most popular structures for diverting water in steep rivers. Intake systems may be used in ephemeral rivers beds to capture part of the runoff flow in the rainy season. Their behavior has mainly been studied in the laboratory. Nevertheless, it is not possible to analyze the whole problem of characterization with traditional methodologies due to the many effects that occur on the bars. Computational fluid dynamics simulations have been considered as a complement to improve the knowledge of the hydraulic phenomenon. However, the geometry of circular racks may be a challenge due to its complexity. After the validation procedure, the numerical models appear to be a good tool to design intake systems. No remarkable differences were obtained between the three two-equation turbulence models tested. The results show differences of less than 1% in flow profile over the rack. Fit curves have been proposed to estimate the flow profile over the rack with r 2 > 95%. Expressions to calculate the discharge coefficient and the collected water through the rack in the clear water case have been proposed and show a good agreement with the laboratory data.

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“…(Garot [25]; Bouvard & Kuntzmann [4]; Noseda [12][13]; Frank [5]; Brunella et al [2]). Hence, the 100 orifice equation is:…”

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Experimental and Numerical Modelling of Bottom Intake Racks with Circular Bars

Carrillo

García

Castillo

2018

Water

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“…Nevertheless, over the bottom intakes, the flow becomes highly three-dimensional so that three-dimensional models were developed and considered (Castillo & Carrillo [4]). Kuntzmann and Bouvard [16] presented a first computational approach for the free-surface profile over bottom racks by assuming constant energy head and a conventional orifice equation. The spatial distribution of discharge as a function of the streamwise coordinate resulted in an ordinary differential equation of the sixth degree, which was solved for the horizontal bottom rack.…”

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confidence: 99%

Numerical Study of Sediment Flow Over Bottom Intake Racks With Flow-3D

Shahri

Khoshnevis

Bina

et al. 2019

int.jour.sci.res.mana.

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Bottom intakes are the most useful structure for diverting the flow of steep rivers and providing specific amount of water for hydropower usage. It is crucial to obtain optimum of physical parameters in order to divert desired discharge with minimum possibility of occlusion. Numerical models can simulate flow and turbulence transport equations at any complex geometries. Numerical methods based on Computational Fluid Dynamics (CFD), are one of the most common methods of numerical simulation that is used in water structures. According to the capabilities of numerical methods, complex modes of flow field over bottom intakes can be analyzed. In the present study, Flow-3D software is used to investigate the experimental results of the previous researcher for sediment and clean water flow over bottom intake with circular bars numerically. This study is carried out in a total of 27 models for clean water and 9 models of sediment flow (Bed-Load) at different approaching flow conditions. Parameters of roughness, size of computational cell, turbulence transport equation, Bed Load Transport equation and bed load coefficient has been calibrated. Validation procedure proved that the accuracy and performance of numerical models appear to be acceptable for designing intake systems. For each test, the discharge coefficient is computed, then by using dimensional analysis, a dimensionless relation derived from the dependent and independent variables and compared with the measured discharge coefficient. Estimating the discharge coefficient by the proposed equation in clean water flow performed a mean error of 6.4 percent and for sediment flow led to a mean error of 4.3 percent.

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“…The efficiency of the intake structure depends on several factors, such as the shape of the bars, net spacing between them (void ratio), amount of flow and flow conditions, initial flow depth, and angle and length of the rack. Many researchers have conducted studies to design the minimum rack area required to transmit the maximum flow rate (Garot [1]; Bouvard [2]; Kuntzmann and Bouvard [3]; Noseda [4]; Noseda [5]; Noseda [6]; Mostkow [7]; Brunella et al [8]). There are some assumptions in these studies; the flow on the rack is one-dimensional, the flow gradually decreases, the hydrostatic pressure distribution acts on the rack in the flow direction, and the energy level or energy head is constant along the rack.…”

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confidence: 99%

Application of Three-Dimensional CFD Model to Determination of the Capacity of Existing Tyrolean Intake

Bor,

Szabo-Meszaros,

Vereide

et al. 2024

Water

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CFD models of intakes in high-head hydropower systems are rare due to the lack of geometric data and cost of modeling. This study tests two different types of software to see how modeling can be performed in a cost-effective way with scarce input data and still have sufficient accuracy. The volume of fluid (VoF) model simulations are conducted using both ANSYS Fluent and OpenFOAM. The geometry is modelled from Google Earth satellite images, drone scanning data, and design drawings from the construction period and supported by field observations for extra quality control. From the model, both capacity parameters and flow pattern are calculated. For capacity, the Cd factor is calculated and compared with the literature. The simulations are conducted for a Tyrolean weir with rectangular bars (flat steel) in the rack. Simulated flow patterns through the rack with ANSYS Fluent and OpenFOAM are compared. OpenFOAM simulations yielded 15% to 20% higher water levels compared to the VOF model applied in Ansys Fluent. Also, when the flow rate was high, the water capture capacity calculated with ANSYS Fluent was 10% higher than that obtained with OpenFOAM. However, considering the total simulation times, modeling with OpenFOAM offered approximately 11% faster results.

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Étude théorique des grilles de prises d'eau du type « En-Dessous »

Cited by 20 publications

References 0 publications

Experimental and Numerical Modelling of Bottom Intake Racks with Circular Bars

Experimental and Numerical Modelling of Bottom Intake Racks with Circular Bars

Numerical Study of Sediment Flow Over Bottom Intake Racks With Flow-3D

Application of Three-Dimensional CFD Model to Determination of the Capacity of Existing Tyrolean Intake

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