Clear-water scour and flow field alteration around an inclined pile

Kitsikoudis, Vasileios; Kirca, V.Ş. Özgür; Yağci, Oral; Çelik, Mehmet Furkan

doi:10.1016/j.coastaleng.2017.09.001

Cited by 40 publications

(27 citation statements)

References 28 publications

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“…The influence of the rotating turbine was significant to the seabed at a low clearance condition, but it was insignificant for a high clearance. The maximum scour depth for a tidal turbine with a tip clearance of 1.0 D t was 0.9 D s , which is close to the cylinder scour depth of 1.11 D s , 1.0 D s , and 1.0 D s found by Zhao et al [35], Kitsikoudis et al [36], and Yao et al [37], respectively. The tidal turbine had a deeper scour pit compared to the cylinder monopile when the tip clearance of the tidal turbine was small, which was 0.5 D t in the current work.…”

Section: Seabed Scour Profilesupporting

confidence: 80%

“…Tidal turbine scouring has an analogous profile and moving trend compared to cylinder scouring, as shown in Figure 11. The maximum scour depth for a tidal turbine with clearances C/D t = 0.5 and 1.0 was compared to the cylinder scouring experiments by Zhao et al [35], Kitsikoudis et al [36], and Yao et al [37], as listed in Table 4. The monopile-supported tidal turbine scouring was analogous to the single monopile when its turbine was placed at a position with sufficient height.…”

Section: Seabed Scour Profilementioning

confidence: 99%

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Tip-Bed Velocity and Scour Depth of Horizontal-Axis Tidal Turbine with Consideration of Tip Clearance

et al. 2019

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The scouring by a tidal turbine is investigated by using a joint theoretical and experimental approach in this work. The existence of a turbine obstructs a tidal flow to divert the flow passing through the narrow channel in between the blades and seabed. Flow suppression is the main cause behind inducing tidal turbine scouring, and its accelerated velocity is being termed as tip-bed velocity (Vtb). A theoretical equation is currently proposed to predict the tip-bed velocity based on the axial momentum theory and the conservation of mass. The proposed tip-bed velocity equation is a function of four variables of rotor radius (r), tip-bed clearance (C), efflux velocity (V0) and free flow velocity (V∞), and a constant of mass flow coefficient (Cm) of 0.25. An experimental apparatus was built to conduct the scour experiments. The results provide a better understanding of the scour mechanism of the horizontal axis tidal turbine-induced scour. The experimental results show that the scour depth is inversely proportional to tip-bed clearance. Turbine coefficient (Kt) is proposed based on the relationship between the tip-bed velocity and the experimental tidal turbine scour depth. Inclusion of turbine coefficient (Kt) into the existing pier scour equations can predict the maximum scour depth of a tidal turbine with an error range of 5–24%.

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Section: Seabed Scour Profilesupporting

confidence: 80%

Section: Seabed Scour Profilementioning

confidence: 99%

Tip-Bed Velocity and Scour Depth of Horizontal-Axis Tidal Turbine with Consideration of Tip Clearance

et al. 2019

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“…Altering vegetation arrangement in the longitudinal direction had more effect than a change in the transverse direction [23]. In their investigations on rigidity, Schlichting [25], Armanini et al [26], Kitsikoudis et al [27] demonstrated how bent vegetation decreased drag coefficient, erosion, and the overall disturbance on the channel bed.…”

Section: Introductionmentioning

confidence: 99%

Effects of Vegetation Density and Arrangement on Sediment Budget in a Sediment-Laden Flow

Tfwala

Chen

2018

Water

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Understanding the effects of riparian vegetation under sediment-laden flow is becoming crucial due to the increase in frequency of extreme weather events. This study designed three densities and nine random distributions of bent flexible vegetation in flume experiments under sediment-laden flow. Sediments were continually added to the flume at a rate of 21 kg/h to simulate a natural river environment in a sediment-laden flow. The results showed that the evolutionary process of bed form under sediment-laden flow could be divided into four stages: scouring, development, recovery, and deposition stages, forming a dynamic cycle. Dunes were formed and backwater caused them to develop upstream, while structural resistance developed the dunes downstream. Contrary to clear water regime, sediments were deposited upstream of the vegetation area and scour occurred behind the vegetation. In addition, the vertical velocity profile showed to be dependent on the vegetation structure and four clear zones were identified: fixed, bent, canopy, and developed zones. The findings from this study provide crucial information towards river management through understanding the diverse vegetation effects under sediment-laden flows.

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“…They found that the horseshoe vortex plays an important role when the inclination angle is small, while the wake vortices gradually dominate the scour as the inclination angle increases. The upward flow in the wake vortices close to the bed becomes stronger with an increasing inclination angle, as indicated by Kitsikoudis and Kirca [22] in their investigation for unsubmerged downstream-inclined cylinders.…”

Section: Introductionmentioning

confidence: 65%

Effect of Inclination Angles on the Local Scour around a Submerged Cylinder

Wang

Yang

et al. 2020

Water

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In ocean engineering and coastal environmental studies, local scour around a submerged structure is a typical issue, which is affected by the inclination of the structure. To investigate the effect of inclination directions and angles on flow structure and the bed morphology, a three-dimensional numerical model of a submerged inclined cylinder was established. In this model, the hydrodynamics are solved from the RANS (Reynolds-averaged Navier–Stokes) equations closed with the RNG k-ε turbulence model, while the bed morphology evolution is captured by the sediment transport model. In the case of vertical-cylinder scour, the simulation results agree well with existing laboratory experiments. In the cases of inclined-cylinder scour, the results show that the inclination direction not only changes the intensity and the location of the downflow but also modulates the pattern of the horseshoe vortex in front of the cylinder, thus influencing the local scour depth and the morphology of the bed. Compared with the case of vertical cylinder, the scour around an upstream-inclined cylinder is deeper, mainly due to the enhancement of downflow in front of the cylinder. The scour around a downstream-inclined cylinder is shallower and broader due to the weakened downflow and accelerated incoming flow. The maximum scour depth decreases with the inclination angle in the downstream-inclination case. In the upstream-inclination case, the maximum scour depth does not vary monotonously with the inclination angle, which results from a competitive effect of the horseshoe vortex and downflow in the front of the cylinder.

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Clear-water scour and flow field alteration around an inclined pile

Cited by 40 publications

References 28 publications

Tip-Bed Velocity and Scour Depth of Horizontal-Axis Tidal Turbine with Consideration of Tip Clearance

Tip-Bed Velocity and Scour Depth of Horizontal-Axis Tidal Turbine with Consideration of Tip Clearance

Effects of Vegetation Density and Arrangement on Sediment Budget in a Sediment-Laden Flow

Effect of Inclination Angles on the Local Scour around a Submerged Cylinder

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