The Effects of submerged vanes inclination angle on sediment transport into sub-channel

permanent

economical solution, by limiting the cross-section of the channel, the deposit of these sediments in the sub-channel decreases the capacity of these rivers to transport water [5].In the case of the diversion channel, the greatest challenge faced is channel blockage and restricted capacity caused by the sedimentation at its entry point.It is the vortex region (separation zone) that determines the practical width for the passage of the flow because the sediments are accumulated in this vortex region at the entry point of the lateral channel.Therefore, identification of the vortex region or flow separation zone, as it is also termed, becomes imperative as shown in figure 1. [6].

Figure 1 Flow Characteristics of a dividing flow in open channels
This can decrease the entry's effectiveness and effective width while increasing sediment deposition at the entrance [7].As mentioned in [8] for erosion and sedimentation to occur, a comprehensive understanding of the sediment deposition characteristics at the intersection of the main channel and the sub-channel is required.[9] argued that these intersections' flow is quite complicated and has been extensively researched.[9] confirmed that focuses the design engineer's attention on the division of water at the junction and the provision of measurement tools that determine the quantity of water flow in each channel.However, what will become of the sediments carried by the primary channel?And how it will divide at the junction, as well as whether or not it is possible to quantify or estimate the quantity of sediments that will enter the sub-channel.And consequently knowing the amount of damage that will be caused by the accumulation of sediments in the sub-channel.Priority must be given to understanding how to prevent or limit sub-channel entry.The primary sediment transport mechanism governs the shape and growth of the bifurcation, which controls the distribution of sediment discharge into two branches.
As can be seen in Figure 2, submerged vanes, which are often represented by regular geometric shapes and serve the purpose of controlling the submerged vanes, are positioned in the main channel and front of the sub-channel.

Figure 2
The design of the vanes system layout [12].
The submerged vane can be fully submerged or partially submerged, but the last one is more common [10].[11] noted that because they are less expensive than conventional river training structures, these submerged vanes have been employed for engineering purposes within rivers, such as altering the flow pattern or reducing erosion around river bends.For sediment management in alluvial rivers, a submerged vane is a vortex-generating device that can influence the evolution of the river bed.In both laboratory trials and field operations, it has proven to be effective.Many of the elements affecting the performance of the submerged vane are hydraulic parameters, such as the main and sub-channel discharge.The velocity of the water, the breadth of the primary and secondary channels, as well as the quantity and kind of sediment.In addition to the nature of the channel's bottom (whether it contains sediments or not, the angle of the sub-channel connection, the straightness of the main channel, etc.), some other factors must be considered.In addition, several variables influence the geometrical properties of the submerged vanes, such as their number, size, shape, and arrangement, as well as their distance from the sub-entrance channels, In order to first compare them and then show which elements have a significant impact, the researcher fixes some aspects while altering others The study of [17][18] shows altering one or more of these variables has a direct effect on the amount of sediment that will enter the sub-channel.The researcher is fixing some factors and varying others to first examine the difference between them and then provide a picture of the variables that have a substantial and influential effect on the dependent variable.Secondly, sub-channels must be taken into account when designing or managing them.Therefore, sediment entry is the vane angle relative to the flow direction, which is regarded as one of the most critical characteristics influencing the strength of the secondary flow.Numerous submerged vanes row sedimentation plans have been evaluated for their effectiveness in preventing the transfer of sediments into the subchannel and the formation of the sedimentation zone qr (the ratio of the sub-channel discharge to the main channel discharge)Therefore, sediments enter the sub-channel numerous scholars have studied and produced numerous types of submerged vanes concerning their size, angle of connection with the direction of flow, and effect on the amount of sediments [18] [19].After seeing that a two-row vane field prevented sediments from entering the diversion for qr values of less than 20%.The researchers determined that adding a third row would not increase desilting performance.For qr levels greater than 20%, the vane field proved less effective.The construction of vortices that resuspend sediments likely to be conveyed did not prevent sediments from entering the diversion [20].
None of the investigations on submerged vanes involved sediment entering the main river.In this study, the outcomes of tests with and without submerged vanes in front of a 90-degree diversion channel under sediment feeding (6 kg/hour) are compared.Many variables affect the performance of vanes in descaling, so this research showed the effect of one row of submerged vanes in treating the amount of sediment entering the outlet channel at an angle of (10°, 20°, 30°, and 40° ) with three side discharge (19.1, 27 and 30.5 l/s) and with different numbers of submerged vanes (3, 5, 7 and 1).

EXPERIMENTAL PROCEDURE
Figure 3 shows the dimensions of a recirculating sediment channel developed for practical experiments at the College of Engineering/Wassit University.
1.The primary channel (10 m in length, 0.3 m in width, and 0.45 m in height) is built of steel, at the end of the channel, there is a tank below ground level (4 m x 3 m x 2.5 m) with a submersible pump.With a 4inch plastic pipe, the pump is connected to the channel.Hence, the end of the channel is poured with a perforated steel tank (tank-2) (60 cm× 60 cm ×60 cm).This then feeds water into the tank, where it circulates throughout the system.2. The sub-channel branch off from it at a distance of (8.73 m) from its beginning.It pours into a perforated tank (tank-1), which later pours into the main tank.At the end of it, a gate is manually controlled.
The main and sub-channels are carried on steel arms 80 centimeters above the ground for convenience of usage, viewing, and measurement.A rectangular weir was constructed, 10 cm high, 30 cm wide, and 35 cm from the end of the main channel.
A two-pipe that is four inches in diameter and has two open ends are as follows: 1.The first one is to drain water from the collection basin to the main tank (by gravity) having a mechanical valve to regulate how much water to manually eject from the basin.
2. The other pipe is attached to the submersible pump, and the other end is connected to the collection basin.The calibration was carried out in the following manner: 1. Close the sub-channel completely during the calibration process.
2. Operation of the main pump at full capacity throughout the calibration period.
3. The valve in the pipe exiting the collection basin will initially be closed, causing the whole flow of water from the pump to be directed into the main channel.More to add, placing a certain amount of water in a tank with defined dimensions and measuring the discharge going through the line coming from the main pump using (60 cm ×60cm×60cm)(Tank-2).As a result, we now have a specific volume of water at a known time (using a stopwatch), as this tank moves on a rail for easy emptying of water from it every time 4. Once a simple opening is formed in the external mechanical valve, part of the collected water will come out of the collection basin, thus the amount of water entering the main channel will decrease, and step (3) will be re-worked, where a new discharge will be obtained, but with a time greater than the previous time.5. Repeating the previous work (4) by making a larger opening in the valve each time to reduce the amount of water that enters the main channel, step (3) which will be repeated to obtain a new volume of water will require more time to complete.6.The procedure in (3,4,5)was repeated ten times.And every time we have a set amount of water with time.7. Establishing a relationship between the volume of water obtained manually with time (Q) and the head of water in the weir (H) shown in Figure 4, the discharge equation is deduced which is: Where: Q=discharge ( 3 /s).H=head of water(cm).

Figure 4
The Relationship Between H (cm) and Q (m3/s).
The sand that was to be fed into the main channel was done so with the assistance of this equipment.It contains a shaft that is attached to an electric motor that has variable speeds, a specific weight of 1100 kg/m3, and a  50 value of 0.4 millimeters, it allows sediment to enter main channel regularly over time.asshown in Figure 6.It was determined that the discharge of the submersible pump was equal to 26 liters per second, and there were found to be three sub-discharges in the side channel (qr).These sub-discharges made up 19.1%, 27%, and 30.5% of the total discharge.Three experiments were conducted without the use of submerged vanes, where (7) submerged vanes were placed in front of the entrance to the sub-channel as shown in Figure 7 and the number of these submerged vanes decreased in each experiment to become (5,3 and 1), and the slope of the submerged vanes is variable (40°, 30°, 20°, 10°), The dimensions of the submerged vanes made of transparent glass were as follows (height 3.5 cm, length 10 cm, and thickness 0.4 cm), 10 cm apart from each other and 7 cm from the channel wall, noting that the height of the water in the channel was 17 cm,as shown in Table 1.

Figure 7
Sub-Channel Created Section.
Sediment was gathered for a period of two hours.Two hours corresponded to approximately the amount of time needed for a dune to move beyond the face of the diversion [21].
Table 1 Standard limits for the design and layout of submerged vanes parameters*

RESULTS
The main objective of this research is to know the effect of using submerged vanes on the amount of sediments, entering the sub-channel, when feeding sediments by (6 kg/h) in the presence and absence of submerged vanes, using main discharge, and three sub-discharges with a variable number of submerged vanes (7, 5, 3 and 1).Figures 6,7,8, show the relationship between the proportion of incoming sediments (Sr=weight in kg of sediments taken in sub-channel /Total sediment feeding (6 kg/h)) and the number of vanes, to obtain the least amount of sediments:

Experiments without submerged vanes
Three experiments were conducted, without submerged vanes shown in table (2), where, at the beginning of the experiments, the three sub-discharge were used with the sediments injection process, the results were fixed, and the amount of sediments that entered into these experiments was the largest.

Experiments with submerged vanes
1.When the sub-channel discharge is 30.5 l/s, the percentage of isolated sediments is approximately between 40% and 50%, as using one piece of submerged vanes, this percentage of isolation gradually improves when increasing the number of submerged vanes, where the percentage of sediments insulation is confined approximately between 12% and 26%, at the use of 7 submerged vanes, with different inclination angles for the rows of submerged vanes, as shown in Figure 8. 2. When the sub-channel discharge is 27 l/s, the percentage of isolated sediments is approximately between 24% and 33%, as using one piece of submerged vanes, this percentage of isolation gradually improves when increasing the number of submerged vanes, where the percentage of sediments insulation is confined between approximately 15% and 24%, at the use of 7 submerged vanes, with different inclination angles for the row of submerged vanes, as shown in Figure 9. 3. When the sub-channel discharge is 19.1 l/s, the percentage of isolated sediments is approximately between 24% and 33%, as using one piece of submerged vanes, this percentage of isolation gradually improves when increasing the number of submerged vanes, where the percentage of sediments insulation is confined between approximately 15% and 24%, at the use of 7 submerged vanes, with different inclination angles for the row of submerged vanes, as shown in Figure 10.

CONCLUSION AND RECOMMENDATION
After examining the curves depicted in the preceding illustrations for three distinct discharges (30.5, 27and 19.1 l/s).And inclination angles for the submerged panels and the number of four angles (10°, 20°, 30°, and 40°) where the number of submerged vanes was altered to (1, 3,5, and 7) the following was observed: 1.There is a relationship between the discharge used in the sub-channel and the percentage of isolated sediments (Sr), as it was noted that the less the discharge of the sub-channel, the better the performance of the submerged vanes, and therefore it is better to use this technique in the sub-channels with few discharges, which reduces the percentage of discharge of sediments the private sub-channel to less than 20%.2. The percentage of isolated sand increases when the number of submerged vanes increases, but this feature is evident for high drainages, and its effect is almost limited for low drainages.3. The performance of the 20 degree angle outperforms all other angles for all discharges that have been used.
This result is consistent with the research [15], in which the researcher regarded angle 20 as the ideal angle and utilized intake ratios ranging from 0.16 to 0.4.There is a priority given to angle 20ᵓ. 4. For all used discharges, the performance of the angle of 20 degrees is better than the performance of the rest of the angles.The decision to use this angle as per the findings of one of the studies [15], in which the researcher regarded angle 20 as the ideal angle and utilized intake ratios ranging from 0.16 to 0.4.There is a priority given to angle 20ᵓ.The outcomes of the study allow for the following experimental tests to be suggested for additional research to improve the performance of the vane: 1-Determine how the impact is affected by a variety of lengths and slopes of the intake channel.
2-When using this alignment, use two or three rows of submerged vanes in front of the intake.

Figure 3
Figure 3 Illustration of The Manufactured Channel.

Figure 5
Figure5illustrates a sand feeder, which is a machine made of moisture-resistant cast iron and is put on top of a cone-shaped main channel trough.

Figure 8
Figure 8 Shows That the Sub-Channel Discharge is 30.5 l/s With Different Angles of Inclination.

Figure 9
Figure 9 Shows That the Sub-Channel discharge is 27 l/s With Different Angles of Inclination.

Figure 10
Figure 10 Shows That the Sub-Channel Discharge is 19.1 l/s With Different Angles of Inclination.

Table 2
Relationship between the Discharge of Sub-Channel & %Sr