Control of sediment inflow into a trapezoidal intake canal using submerged vanes
01 Nov 2018-Journal of Waterway Port Coastal and Ocean Engineering-asce (American Society of Civil Engineers)-Vol. 144, Iss: 6, pp 04018020
TL;DR: In this paper, experiments were conducted to control sediment entry into an intake channel using submerged vanes in a physical model with a rectangular mobile-bed main channel and a trapezoidal rigid-bed intake channel diverting at an angle of 45°.
Abstract: Intake canals are used to withdraw water from rivers for various purposes. Sedimentation in the intake canal reduces the quality and quantity of water being delivered. In this study, experiments were conducted to control sediment entry into an intake channel using submerged vanes in a physical model with a rectangular mobile-bed main channel and a trapezoidal rigid-bed intake channel diverting at an angle of 45°. The variables in the study included vane angle, number of vane rows, and vane spacing in terms of mean flow depth in the main channel. In addition to the commonly used vane array with uniform vane heights, three other vane-height configurations were also tested. The least local scour around vanes and highest sediment reduction (~70%) were observed for vanes oriented at a 15° vane angle with an increasing vane-height configuration placed in two rows. It was also observed that control of sediment entry into the intake canal increased with an increase of both vane spacing and number of vane rows.
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TL;DR: In this paper, a method for sediment control in damless water intake hydraulic units consisting in artificial transverse circulation (ATC) generated by redistributing specific water flow rates in the cross-section of the supply channel is described.
Abstract: Abstract Introduction. In this article, we describe a method for sediment control in damless water intake hydraulic units consisting in artificial transverse circulation (ATC) generated by redistributing specific water flow rates in the cross-section of the supply channel. One of the simplest and most effective anti-sediment elements working according to this principle is the submerged vane (SV). The intensity of the ATC formed in the flow depends on the flow regime and the planned-geometric characteristics of the vanes. Available recommendations on the selection of the rational characteristics of SV under the conditions of river damless water intake appear to be contradictory, thus requiring clarification. This study is aimed at examining the interaction between SV and a model flow without water trapping under various planned-geometric characteristics of the vane and experimental hydraulic regimes of its work using a physical model of the errosion-resistant channel. In addition, we set out to assess the effect of essential parameters on the intensity of the ATC generated in the flow. Materials and methods. This research was based on physical modelling hydraulic studies and theoretical calculations. Five hydraulic modes of vane operation with different planned-geometric characteristics were studied using a physical model of the erosion-resistant channel. Multiple regression analysis of the obtained experimental data was carried out. Results. The results of laboratory hydraulic studies on the SV operating conditions are presented. Experimental dependencies characterising the intensity of the ATC generated in the flow are plotted. A multiple regression equation is derived for the amount of the data obtained. Conclusions. It is established that the relative height of the vane and its angle to the side of the flume (coastline) has a significant effect on the intensity of the generated ATC. It is experimentally confirmed for the first time that SV shows little efficiency in high water horizons in terms of in-flow ATC generation.
3 citations
TL;DR: Submerged vanes have been used extensively for sediment deflection in river training tasks as discussed by the authors , such as river bends protection, sediment exclusion at water intakes, improving safety at bridges on waterways, and improving inland navigation.
Abstract: Diverting or deflecting sediments is an essential part of river training. Under the effect of an induced helical motion, the submerged vanes are best known for deflecting sediments. This study presents current state-of-the-art information on employing submerged vanes for sediment deflection, as well as concluding notes outlining the current knowledge’s limitations and suggestions for future research on sediment deflection using submerged vanes. The analytical background for basic physics of submerged vanes’ operation is first described. The paper then moves on to a thorough examination of vane design parameters based on analytical relationships. A brief overview of the applications of submerged vanes is also included in the paper. A review of recent studies aims at designing a layout of submerged vanes to assist in river training tasks, such as river bends protection, sediment exclusion at water intakes, improving safety at bridges on waterways, improving inland navigation is provided to this end. The study also presented a future program of research on submerged vanes for improving inland navigation in braided rivers. The major lag in literature is a lack of information on macro turbulence and the associated sediment motion induced by the wake of the submerged vane.
2 citations
TL;DR: In this article , the effects of geometrical vane parameters and specific water discharge ratios on the desilting efficiency of submerged vane fields and on the bed morphology around a 90° lateral water diversion were investigated.
Abstract: The design criteria of submerged vane fields used to control the transfer of sediments into lateral channel diversions have been mostly based on suggestions of some fundamental studies on vane fields aiming to protect riverbanks against erosion. Indeed, although there are studies that investigate the effect of some characteristic parameters of submerged vanes on the desilting of lateral diversions (prevention or reduction of lateral sediment ingestion), they do not adequately cover all pertinent parameters and their significant ranges. In view of the gap of knowledge resulting from this incomplete parametric coverage, an investigation comprising 26 experiments was conducted. It investigated the effects of geometrical vane parameters and specific water discharge ratios on the desilting efficiency of submerged vane fields and on the bed morphology around a 90° lateral water diversion. The vanes displayed skew angles between 10° and 50°, and their heights were 0.2 to 0.4 times the approach flow depth. The distance from the channel bank to the inner vane row and the streamwise distance between vane arrays were, respectively, 0.7 to 1.5 and 2.0 to 3.0 times the approach flow depth. The specific water discharge ratio, qR, varied between 0.1 and 0.3, and the number of vane rows was 6 and 3. The skew angle and the specific water discharge ratio were the most effective parameters on desilting, whereas the others had a small effect within the experimental limits of this study. The optimal desilting efficiency, ≈94%, was achieved when the skew angle was equal to 45° and qR was kept in the range of 0.1 to 0.2.
1 citations
TL;DR: In this article , 2-array submerged vane structures were investigated in the meandering part of open channels, both laboratory and numerically with an open channel flow discharge of 20 L/s.
Abstract: In the case of flooding in rivers, river regulation structures are important since scours occur on the outer meander due to high flow velocities. In this study, 2-array submerged vane structures were investigated which is a new method in the meandering part of open channels, both laboratory and numerically with an open channel flow discharge of 20 L/s. Open channel flow experiments were carried out by using a submerged vane and without a vane. The flow velocity results of the computational fluid dynamics (CFD) models were compared to the experimental results and the results were found compatible. The flow velocities were investigated along with depth using the CFD and found that the maximum velocity was reduced by 22-27% along the depth. In the outer meander, the 2-array submerged vane with a 6-vane structure was found to affect the flow velocity by 26-29% in the region behind the vane.
TL;DR: In this article , the effect of 3-array submerged vane structures on flow velocities was investigated experimentally by using 3array submerged Vane structures in areas close to the outer bank.
Abstract: Regulation structures such as submerged vane are needed to reduce and eliminate environmental damage due to increased flooding in rivers. In particular, scours on the outer bank due to increased flow velocities cause the river bed to change and deteriorate. In this study, the effect on flow velocities was investigated experimentally by using 3-array submerged vane structures in areas close to the outer bank. The experimental vane results were performed in the open channel setup. The Computational Fluid Dynamics (CFD) results obtained with the numerical model were also verified and compared with experimental results. It has been observed that the CFD model gives results close to the real experimental results. The standard-based k-ε model was used as the turbulence model. In the outer meander, the 3-array submerged vane with a 3-vane structure was found to affect the flow velocity by 16–27% in the region behind the vane. The flow velocities were investigated along with depth using the CFD and found that the mean velocity was reduced by 14–21% along the depth. It is also recommended that submerged vane structures can be applied as an effective method in reducing flow velocities and directing flows.
References
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TL;DR: In this paper, the physics of the flow past a submerged vane is analyzed by solving the fully three-dimensional Reynolds-averaged Navier-Stokes equations in conjunction with the standard two-equation k-t turbulence closure.
Abstract: Details of recently undertaken numerical study to analyze the physics of the flow past a submerged vane is presented. The numerical model solves the fully three-dimensional Reynolds-averaged Navier-Stokes equations in conjunction with the standard two-equation k-t turbulence closure. The governing equations are formulated in generalized boundary-fitted coordinates to accurately resolve the bed topography and the shape of the vane. The bed roughness effects are introduced by means of a two-point wall functions approach. The predictions from the numerical model are compared against measurements from an experimental study performed in a deformable-bed straight rectangular channel. Detailed experimental measurements of all three components of velocity, both in the neighborhood as well as in the far field of the vane are compared to judge the performance of the numerical mod
35 citations
TL;DR: In this article, an experimental study was performed in a straight rectangular flume with a lateral canal to understand flow separation at the water intake, five different types of intake with 45, 56, 67, 79 and 90° were installed on one side of the straight canal.
Abstract: A water intake is normally used to divert water from the main canal and river into the water distribution network, secondary canals and turbine systems. The flow structure at the water intake is very complicated due to flow separation. The water intake is usually installed at right angles to the main channel flow direction, where the right angle water intake produces a large separation zone inside the intake and reduces flow discharge. Thus, the optimum installation angle of a water intake is very important to minimize the separation zone at the mouth of the intake. In this study, an experimental study was performed in a straight rectangular flume with a lateral canal to understand flow separation at the water intake. To find the optimum angle of the water intake, five different types of intake with 45, 56, 67, 79 and 90° were installed on one side of the straight canal. Two components of flow velocity were measured using an electromagnetic disk type velocity meter (PE-30 Type, DELFT). The velocity of the flow inside each intake was measured at 729 points in a fine grid, including 243 points at three horizontal layers and 486 points in six cross-sections. At similar flow condition, the size of separation inside the intakes was measured from the plotted streamlines and compared for the five types of the intakes. Here, the water intake with minimum separation zone was defined as the optimized water intake. From the statistical analysis, it was found that minimum separation size forms in a 55° water intake. Therefore, the optimum angle for installation of water intake with minimum separation is 55°. Copyright © 2005 John Wiley & Sons, Ltd.
27 citations
TL;DR: In this article, a new approach to analyze the interaction among a row of submerged vanes is described, and the results show that the sediment management capacity of a vane system comprising three vanes in a row decreases when the vane spacing is reduced.
Abstract: A new approach to analyze the interaction among a row of submerged vanes is described. Submerged vanes are small foil-like elements mounted vertically on the channel bed to modify the flow pattern and the sediment distribution within its cross section. Usually a number of vanes are arranged in a row to widen the affected area. Due to the interaction among the vanes, the sediment control capability of a vane system diverts from simple superposition of individual vanes.A new methodology is developed to model this interaction. The results show that the sediment management capacity of a vane system comprising three vanes in a row decreases when the vane spacing is reduced. Upon these three vanes, the declination of the inner vane is especially evident. When the spacing between the vanes is smaller than about 0.6 vane lengths, the center vane has nearly half function left. An investigation on vane systems comprising different numbers of vanes shows that their efficiency decreases due to the interaction among t...
20 citations
TL;DR: In this article, the possibility of the submerged vanes to control and direct the flow and river thalweg toward the intake port with different longitudinal arrangements has been investigated and three longitudinal distances 3H, 4H, and 6H (H being the initial height of the vanes) have been considered and the experiments have been done for the regular and irregularity.
Abstract: Constructing intake structures to divert some part of the flow from rivers causes some changes in hydraulic conditions of the flow in front of the intake port. These changes, like flows in river bends, induce secondary flows, thereby causing sedimentation in the intake port and erosion in the bank facing the intake. Submerged vanes have been used for different purposes such as reducing erosion in river bends, bank stabilization, increasing flow into the intake and so on. The vanes are typically installed with an angle of 15°–25° to the flow direction and with an initial height of about 20%–50% of the flow depth (Marelius and Sinha, 1998; Nakato et al., 1990). In this study, the possibility of the submerged vanes to control and direct the flow and river thalweg toward the intake port with different longitudinal arrangements has been investigated. Three longitudinal distances 3H, 4H, and 6H (H being the initial height of the vanes) have been considered and the experiments have been done for the regular and ...
20 citations