Velocity Distributions around Blocked Trash Racks

Zayed, Mahmoud

doi:10.1061/(asce)ir.1943-4774.0001598

Cited by 3 publications

(3 citation statements)

References 24 publications

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“…Furthermore, new designs and optimisation of racks have been keeping research and development activities going. Using sophisticated measurements techniques [15,31,[42][43][44][45][46] and computational fluid dynamics simulations [5,17,18,47] served to better understand the flow conditions, especially for studying partially blocked trash racks and conducting ethohydraulic investigations [12][13][14]45,46]. Some references offer specific empirical equations, tables, or graphs to determine the depth difference or hydraulic head loss depending on a vast range of rack configurations [1,36,48,49].…”

Section: Empirical Approaches Based On Bernoulli's Energy Principlementioning

confidence: 99%

“…The recent literature rather reveals studies which yield advanced empirical equations to consider additional effects, especially the occurrence of accumulated ice and aquatic weed upstream of the rack [10,11], or to investigate angled fish-friendly bar racks [12][13][14]. Other recent studies parameterise flow effects behind the rack, such as the velocity distribution [15] and the free-surface depression [16], to yield new design equations that determine the rack head loss.…”

Section: Introductionmentioning

confidence: 99%

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Determining the Flow Resistance of Racks and the Resulting Flow Dynamics in the Channel by Using the Saint-Venant Equations

Baselt

Malcherek

2022

Water

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Racks retain debris in wastewater treatment plants and shield sensitive machinery in numerous engineering applications. In open-channel flows, racks impound the upstream water level by posing local obstacles in the flow. Based on experimental investigations, empirical approaches usually predict the flow resistance by relying on Bernoulli’s energy principle. Since this principle does not correctly consider downstream conditions such as submerged flows, we present a more accurate workflow to determine the flow resistance based on the Saint-Venant equations. We will demonstrate how the loss coefficient and the hydraulic head loss are determined more reliably without adding complexity to the engineering realisation. In contrast to relying solely on two cross-sections with Bernoulli’s energy principle, applying the Saint-Venant equations enables determining the flow depth profile and the flow velocity in the entire channel. This workflow additionally allows predicting the channel’s hydraulic capacity and freeboard in arbitrary applications.

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Section: Empirical Approaches Based On Bernoulli's Energy Principlementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Determining the Flow Resistance of Racks and the Resulting Flow Dynamics in the Channel by Using the Saint-Venant Equations

Baselt

Malcherek

2022

Water

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“…Although numerous researchers have examined the impact of Reynolds number and blockage ratio on head loss properties in open channel flow [10,11,12,13], the turbulence characteristics in the vicinity of trash racks in open channel flow have not yet been comprehensively explored. Hence, in order to fill this research gap, the present investigation aims to examine how the Reynolds number and blockage ratio influence turbulence attributes in the flow over vertical trash screens.…”

Section: Introductionmentioning

confidence: 99%

Effects of Reynolds number and blockage ratio on the turbulence characteristics of open channel flow passing through trash rack

Kokkiligadda,

Dhar,

Reddy Hanmaiahgari

2024

J. Phys.: Conf. Ser.

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Trash racks are extensively used to prevent debris from being transported to down-stream reaches of waterways. However, debris accumulation at the screens can significantly affect their hydraulic performance, resulting in negative economic and environmental consequences. Basic research related to the mechanism of these physical processes is still rather limited. In this experimental study, the flow fields, including the turbulence intensities, Reynolds stresses, and turbulent kinetic energy near a trash rack in a fixed-bed open channel for subcritical flow conditions are investigated for two Reynolds numbers and two blockage ratios. The experimental study investigates the important physical mechanisms relating to turbulence generation and possible sediment deposition induced by the vertical trash rack. Reynolds number effect on time mean streamwise velocity is predominant in the trash rack’s downstream free surface layer as a higher Reynolds number flow has higher normalized streamwise velocity in the free surface layer and lower in the inner layer. In both the Reynolds number effect case and the blockage ratio effect case peak normalized turbulent kinetic energy was observed immediately downstream of the trash rack and with the increment of longitudinal distance downstream of the trash rack, normalized Turbulent kinetic energy is decreased.

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Numerical and experimental analysis of structural optimization and flow resistance effect of safety barrier based on a pump device

Luan,

Yang,

Jiang

et al. 2024

Advances in Mechanical Engineering

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The safety barrier is often positioned at the entrance of the inlet passage in large and medium-sized low-lift pump stations, to ensure the safety of people and animals. To elucidate the blocking effect of the safety barrier and its influence mechanism on the internal flow of the inlet passage, numerical simulation combined with the physical model test were employed to investigate the impact of the cross-section and bar spacing of the safety barrier on the head loss, and the impact mechanism was clarified. The results showed that the optimal cross-section form of the safety barrier was found to be circular from the standpoint of head loss. When the blockage ratio of the safety barrier exceeds 0.3; prompt clearance of the blockage is recommended.

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Velocity Distributions around Blocked Trash Racks

Cited by 3 publications

References 24 publications

Determining the Flow Resistance of Racks and the Resulting Flow Dynamics in the Channel by Using the Saint-Venant Equations

Determining the Flow Resistance of Racks and the Resulting Flow Dynamics in the Channel by Using the Saint-Venant Equations

Effects of Reynolds number and blockage ratio on the turbulence characteristics of open channel flow passing through trash rack

Numerical and experimental analysis of structural optimization and flow resistance effect of safety barrier based on a pump device

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