Turbulence characteristics of flow past submerged vanes

Sharma, Himanshu; Ahmad, Z.

doi:10.1016/j.ijsrc.2019.07.002

Cited by 15 publications

(9 citation statements)

References 37 publications

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“…At cross-sections x = {0.08, 0.13} m, the maxima k were observed where the rising flow was also identified (Figures 13a,c and 15c,e). The same occurred at cross-section x = 0.18 m but, in this case, the turbulent kinetic energy was slightly higher close to the bed, due to the straining action of the diversion vortex (Figure 18c), as implicitly suggested by Sharma and Ahmad [24]. The enhanced turbulent kinetic energy promoted higher mobility of the sediment grains, possibly leading to their transportation in suspension.…”

Section: Turbulent Kinetic Energysupporting

confidence: 69%

“…The cores, depicted in Figure 17(d2), are the imprint of the tip vortices created around the vanes (Figure 8f), as suggested by Barkdoll et al [6]. It can be postulated, in accordance with Sharma and Ahmad [24], that, as the water participated in the vortical motion towards the surrounding flowing water, it strained the neighboring flow layers. The generation of excessive strain in these layers resulted in enhanced Reynolds stresses, which in turn enhanced the turbulent fluctuations and the turbulent kinetic energy.…”

Section: Turbulent Kinetic Energymentioning

confidence: 59%

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Effect of a Submerged Vane-Field on the Flow Pattern of a Movable Bed Channel with a 90° Lateral Diversion

Baltazar

Alves

Bombar

et al. 2021

Water

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This laboratory study focused on the effect of a submerged vane-field on the flow pattern and bed morphology near and inside the entrance reach of a movable bed 90° lateral diversion. The system was modelled under live bed conditions for a water discharge ratio of ≈0.2. Two experiments were run until bed equilibrium was reached: with and without a vane-field installed close to the diversion entrance to control the transfer of sediments into the diversion channel. The equilibrium bed morphology and the associated 3D flow field were measured in great detail. The bed load diverted into the diversion was reduced by approximately one quarter due to the action of the vane-field. The vanes prevented the formation of the diversion vortex in the main channel, upstream of the diversion’s entrance, thus contributing to that decrease. They also created a main channel vortex that started at the most upstream vanes and further decreased the amount of bed load entering the diversion. The flow separation zone inside the diversion was larger with vanes, but conveyance was balanced through a slightly deeper scour trench therein. The flow structures described were confirmed through the measurements of the turbulent kinetic energy.

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Section: Turbulent Kinetic Energysupporting

confidence: 69%

Section: Turbulent Kinetic Energymentioning

confidence: 59%

Effect of a Submerged Vane-Field on the Flow Pattern of a Movable Bed Channel with a 90° Lateral Diversion

Baltazar

Alves

Bombar

et al. 2021

Water

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“…When the water depth reaches its peak ( t T s d = 1), the frequency of occurrence of the outward interaction (quadrant I) and inward interaction (quadrant III) increases due to flow unsteadiness, possibly suggesting the strong interaction of the turbulent structures with the main flow. In order to demonstrate the importance of turbulent bursting (especially the extreme events) to the momentum fluxes, the contributions of large 𝑢′𝑤′ events to total momentum fluxes in different cases are shown in Figure 11, which adopted the top 30%, 20%, and 10% values as the large amplitude bursting events for statistical analysis [35]. The extreme events in momentum exchange are increased because of flow unsteadiness.…”

Section: Turbulent Burstingmentioning

confidence: 99%

Hydrodynamic Characteristics of Strong, Unsteady Open-Channel Flow

Hu,

Huang

et al. 2023

Sustainability

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Due to climate change, the intensity of extreme rainfall has been observed to increase with a shorter duration, causing flash floods (strong, unsteady flow) that lead to serious loss of life and economic damage all over the world. In this study, by repeating the same flume experiments twenty times over a bare bed or with a submerged vane installed, the hydrodynamic characteristics of a strong, unsteady open-channel flow were investigated. Acoustic Doppler velocimetry (ADV) was used to measure the instantaneous three-dimensional velocity, and the ensemble average method was then adopted to obtain the time-varying mean flow velocities. Reynolds decomposition was applied to disintegrate the instantaneous velocity to time-varying average velocity and fluctuating velocity. Turbulence characteristics such as turbulent intensity, turbulent bursting, and power spectral density (PSD) were analyzed against water depth variations. The results show that the loop pattern of the streamwise velocity against the water depth variations could significantly affect the turbulence characteristics of unsteady flow. Near the bed, the peaks of the turbulent intensity and the TKE lag behind the peak of the water depth. The PSD revealed that the turbulent energy increases at the rising and falling stages were due to the generation of small-scale turbulence vortices or eddies. As a submerged vane was present, the increase in the angle of attack caused the increase in the turbulent intensity and TKE, which means that the induced vortex became stronger and the wake region was larger. When the angle of attack was equal to 20°, the TKE abruptly enlarged in the falling stages, implying the breaking-up of the induced vortex. The PSD of the transverse fluctuation velocity showed multiple spikes at the high-frequency part, possibly denoting the shedding frequency from the induced vortex. Further downstream, behind the submerged vane, the peak frequencies of the PSD became imperceptible, likely because of the induced vortex decays or other factors such as the turbulence generated from the free surface or the channel bed mixing with the turbulence from the induced vortex.

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“…Among the different design parameters of submerged vanes, the angle of attack of the vane with the ow is an important parameter, and it has been the subject of various investigations. For example, many researchers studied the effect of vane angle of attack to control and reduce scour [6, 10,13,19,24,25,30,31,32,34,38,40,43,45,46].…”

Section: Application Of Submerged Vanesmentioning

confidence: 99%

Influence of different skew angles of the submerged vane on pressure flushing performance

Beiramipour

Qaderi

Rahimpour

et al. 2022

Preprint

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Siltation is a major threat to the original storage capacity and lifespan of a reservoir. Pressure flushing is an effective measure against siltation through the partial drawdown of the reservoir water level with limited flushed cone volumes in front of the bottom outlet. In this study, a novel configuration with submerged vanes has been proposed and tested experimentally to increase the flushed sediment volume during the pressure flushing operation. In the new configuration, submerged vanes aligned with ten skew angles (θ) of 10°, 20°, 30°, 45°, 70°, 110°, 135°, 150°, 160°, and 170° to flow direction in non-cohesive sediment bed materials were conducted. The results showed that in 45° ≤ θ ≤ 160°, increasing the skew angle increased the flushing cone geometry. The minimum and maximum flushing cone dimensions and volume occurred at skew angles of θ = 45° and 135° ≤ θ ≤ 160° around the bottom outlet. Eventually, nonlinear regression analysis yielded an equation for estimating flushing cone volumes. The developed equation was tested in real case studies of a target reservoir, and an acceptable correlation between calculated and experimental results was obtained.

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Turbulence characteristics of flow past submerged vanes

Cited by 15 publications

References 37 publications

Effect of a Submerged Vane-Field on the Flow Pattern of a Movable Bed Channel with a 90° Lateral Diversion

Effect of a Submerged Vane-Field on the Flow Pattern of a Movable Bed Channel with a 90° Lateral Diversion

Hydrodynamic Characteristics of Strong, Unsteady Open-Channel Flow

Influence of different skew angles of the submerged vane on pressure flushing performance

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