Reduction of local scour at river confluences using a collar

Amini, Nargess; Balouchi, Behnam; Bejestan, Mahmood Shafai

doi:10.1016/j.ijsrc.2017.06.001

Cited by 16 publications

(8 citation statements)

References 39 publications

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“…The increased velocity can cause greater secondary circulations and consequently larger dimensions of scour hole. It is similar to a reported result by Amini et al (2017).…”

Section: Resultssupporting

confidence: 93%

“…Contrariwise, the penetration length of scour hole along the main and lateral channels ( N and P ) was reduced with increase of θ . The more the discharge ratio ( Q r ) was increased, the less effect of side slope angle ( θ ) on the penetration length of scour hole was observed. For Q r = 0.552, the penetration length of scour hole in every direction was almost independent of the side slope angle of main channel ( θ ). The greater the value of Fr g3 , the more development of scour hole was observed in the laboratory model, which is in accordance with the results of Amini et al (). But the present study showed that the effect of Fr g3 was more tangible in the case of milder side slope angles ( θ ). Using the multivariate regression method, some relationships were derived for estimating the penetration lengths of scour hole in different directions in an open‐channel confluence.…”

Section: Resultssupporting

confidence: 88%

“…• The greater the value of Fr g3 , the more development of scour hole was observed in the laboratory model, which is in accordance with the results of Amini et al (2017). But the present study showed that the effect of Fr g3 was more tangible in the case of milder side slope angles (θ).…”

Section: Penetration Of Scour Hole Across the Main Channelsupporting

confidence: 90%

“…In another experimental study, Yuan, Tang, Xiao, Qiu, and Xia () investigated the effect of increasing the lateral discharge to a junction with 90° confluence angle and observed that the location of maximum scour depth moves downstream in parallel to the main channel wall. Amini, Balouchi, and Shafai‐Bajestan () studied the effect of collars on reducing the scour depth in a channel confluence. They found that using a collar for lower discharge ratios can cause a flatter sediment bar and also the reduced scour depth by 100%.…”

Section: Introductionmentioning

confidence: 99%

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Effect of side slope of main channels on formation and penetration of scour hole in confluences

Khosravinia

Nikpour

Malekpour

et al. 2019

River Research & Apps

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In an open‐channel confluence, deep scour holes and depositional point bars are usually formed due to high bed‐shear stresses and secondary circulations. In the present study, presuming the effectiveness of channel geometry on the flow dynamics at the confluence, some variables including different side slope angles of the main channel (θ = 45°, 60°, 75°, 90°), lateral to downstream discharge ratio (Qr), and downstream densimetric Froude number (Frg3) were experimentally studied under clear‐water condition for the confluence angle α = 90°. According to the results, the increase of θ led to a greater penetration of scour hole across the main and tributary channels, whereas a little scour development was observed along those channels. Meanwhile, an increase in Qr and Frg3 caused further scouring, but their effects on the dimensions of scour hole diminished with increase of θ. Thus, with increase of Qr from 0.194 to 0.552, the mean penetration rate of scour hole to all directions for θ = 45°, 60°, 75°, and 90° was obtained 42.8%, 32.4%, 25%, and 20.5%, respectively. In addition, considering the effect of θ, Qr, and Frg3, some empirical relationships were obtained for estimating the penetration length of scour hole. The derived relationships show that Frg3 plays more important role on the dimensions of scour hole than θ.

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“…The increased velocity can cause greater secondary circulations and consequently larger dimensions of scour hole. It is similar to a reported result by Amini et al (2017).…”

Section: Resultssupporting

confidence: 93%

Section: Resultssupporting

confidence: 88%

Section: Penetration Of Scour Hole Across the Main Channelsupporting

confidence: 90%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Effect of side slope of main channels on formation and penetration of scour hole in confluences

Khosravinia

Nikpour

Malekpour

et al. 2019

River Research & Apps

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show abstract

“…In particular, the scouring downstream of the stilling basins had been investigated using the parameters, with and without a sill, different stilling basin geometry, and wide flow pattern (Farhoudi & Shayan, 2014;Champagne et al, 2017;Palermo & Pagliara, 2018;Koochak & Bajestan, 2016;Oliveto & Comuniello;. In recent years, several studies have been done to prevent the scouring downstream of the hydraulic structures (Amini et al, 2017;Heibaum, 2000;Khosravinia et al 2018;Kim et al, 2000;Korkut et al, 2007;Li et al, 2006;Li et al, 2005;Radice & Davari;Bejestan et al, 2015;Zarrati et al, 2010). When these studies are examined, it is observed that the idea of placing a bed sill into the bed material is a good solution (Ben Meftah & Mossa, 2006;Grimaldi et al, 2009;Hamidifar et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

Local scour protection using geocell for downstream of spillway

Gül

Sarıcı

Dursun

2021

JER is an international, peer-reviewed journal that publishes f

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Local scour is an important problem for hydraulic structures. The local scour in the downstream of dams causes problems such as the damage of the dam body stabilization, erosion of the slopes, and the submergence of the turbines. There are many studies investigating the local scour prediction of the downstream of the hydraulic structures, but in recent years, these studies have been replaced by studies of local scour reduction. The new idea of confining the bed materials using the geocell is becoming a popular solution. This solution can be especially used for the reinforcement of the soils. In this study, the preventability of the local scour downstream of chute channel by cellular confinement system, also known as geocell, was investigated. As a result, in case of using geocell, percentage reduction of the maximum scour depth up to 40.63% was observed.

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Experimental investigation of flow pattern over a fully developed bed at a 60° river confluence in large floods

et al. 2022

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River confluences have a complex flow and sedimentation pattern that have vital influences on the hydraulic and bed morphology of river reach and the surrounding area. Confluences can be observed in waterways with various situations such as live bed conditions. This condition is a hydro-morphological situation with a high densimetric Froude number, i.e., bed load transport is supplied from upstream. According to the literature review, most of the experimental studies investigate the flow pattern on the flatbed and not on the developed riverbed, or/and in the low densimetric Froude number, or/and without supplying the sediment from upstream. Therefore, in the present study for the quantification of the flow pattern under these conditions, each developed bed was fixed with the cement blanket method in the laboratory. Then, the 3D velocity was measured at specific points at the confluence. The current study was designed to understand the flow pattern corresponding to the river bed behavior in the case of large floods. It is expected that the morphological features downstream of the confluence have a different pattern than the ones in the condition described in other literature. Thus, this paper describes briefly what are the different bed features and investigates the corresponding flow pattern. The results of the flow pattern on the developed bed show that all zones at the river confluence can be observed except the point bar due to the approximate equality of the mean longitudinal velocity of the separation zone and the main channel upstream of the confluence. Moreover, results show that by increasing the bedload ratio (sediment discharge to water discharge of the main channel of upstream of the confluence) from 0 to 3 × 10−4, flow deflection to the outer bank of the channel decreased down to 45%, the stagnation equivalent area decreased down to 2.5 times, and bed shear stress decreased down to 40%. Hence, the momentum of lateral flow decreased with increasing bedload. Besides, the recovery zone occurred at a longer distance after the confluence compared to the case without bedload. Hence, the location of the maximum velocity zone, vortices, and secondary flows changed downstream of the confluence, by changing the bed load value.

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Reduction of local scour at river confluences using a collar

Cited by 16 publications

References 39 publications

Effect of side slope of main channels on formation and penetration of scour hole in confluences

Effect of side slope of main channels on formation and penetration of scour hole in confluences

Local scour protection using geocell for downstream of spillway

Experimental investigation of flow pattern over a fully developed bed at a 60° river confluence in large floods

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