Effect of longitudinal training wall (LTW) on improving the inlet flow pattern at the side channel intakes

Introduction
One of the problems of most intakes is the accumulation of sediments in the inlet, which significantly reduces their capacity. In addition, sediments entering the intake channel also increase the problems caused by the lack of control of the sediments entering the intakes. Its transfer into irrigation canals and facilities causes many issues due to transporting sediments or settling them in different parts., Pay more attention to controlling sediments in water intake projects to reduce dredging costs and prevent sediments from entering the openings. There are various methods to reduce or prevent sediment entry into the intake inlet. In this research, the effect of several types of structures is investigated to reduce the sedimentation at the intake inlet. So, the effect of the longitudinal separating wall system on the flow patterns of the flow velocity and depth values ​​before the intake inlet was investigated. In this regard, the investigation of the mentioned new structure to modify the flow and sediment pattern for different discharges was carried out experimentally.
 
Methodology
Experimental model
In this research, the physical model of the Hemet intake was built in the hydraulic laboratory of the Faculty of Water and Environmental Engineering, Shahid Chamran University of Ahvaz. The area of the Shahid Hemat Shadgan Irrigation Network Project is ​​9015 hectares at south of Khuzestan province and the Shadgan zone. The water intake of the mentioned project is done from the Jarhari River, and the important networks of this river are as follows. The river model includes a flow-calming basin to minimize the effects of pumping on the formed profiles. At the end of this channel, three sliding gates and a water intake were installed on the channel's left wall. In addition, the separating wall was at a distance of 2m from the side channel. The length of this separating wall was 2m. The required width for the main channel will be 2.2 meters, the height will be about 90 centimeters, and a 79-degree water catchment will be installed at a distance of about 5 meters from its beginning. The required dimensions will be determined based on a scale of 1 to 15 for geometrical dimensions and 1 to 5 to 8 for depth based on the physical conditions of the Hemet reservoir and the Jareh River. In this regard, five flow rates with three values ​​of opening percentage of the end gate of the channel, without the operation of the separating wall, were considered a control test. Then, the tests mentioned in two conditions of submerged and non-submerged walls were also taken to compare the effect of these walls. After the measured flow depth upstream and downstream of the separating wall, in each experiment, the flow rate was taken through the end spillway of the lateral intake. The total flow rate entering the main channel and the end intake spillway reading were compared to calculate the end gate's opening value.
 
Results and discussion
The results of the tests showed that the flow depth at the beginning and end of the separating wall increases with the increase of the total flow rate in the case where the end gates are entirely closed. By comparing the flow depth at the beginning and end of the separating wall, it can be seen that the flow depth after the structure has decreased in all flows. Also, the separating wall does not affect the flow depth in the two states of standing and non-submerged compared to the control state. It was also observed with the velocity measurement that when the flow enters the path of the separating wall, the flow velocity decreases, and the lowest recorded velocity is in the middle of the wall. As the flow towards the end of the wall, the velocity flow will increase. In five discharges, 40, 50, 60, 70, and 85 L/s reduction in velocity was obtained by 60, 55.2, 45.9, 37.5 and 29.4% respectively. In addition, the results of the experiment showed that the operation of the separating wall in the submerged state has increased the flow rate in the lateral catchment. The non-submerged wall also had the opposite result in the same situation and reduced the flow rate in the side channel intake. As can be seen, with the increase in the flow rate, the effect of the walls on the rise in the flow rate of the side aerator has also decreased, and this can be caused by the increase in velocity in the main channel. In all cases, the effect of the submerged barrier is more noticeable than the non-submerged one in increasing the intake discharge. In general, the impact of the separating wall on the increase in flow rate has been practical only in low flow rates.
 
Conclusions
In this research, the effect of the longitudinal training wall (LTW) wall on the hydraulics of the river flow before the lateral intake was investigated. The side wall was installed in two submerged (height 20 cm) and non-submerged (height 40 cm) in the middle of the main channel. Experiments were performed in 5 flow rates of 40, 50, 60, 70, and 85 L/s and in two gate opening states of 30 and 100%. The flow depth before and after the submerged and non-submerged wall was compared with the control condition. The results showed that the submerged wall had a more significant effect on the flow depth than the non-submerged wall. In many discharges, it caused a decrease in the flow depth downstream; three points at the beginning, middle, and end of the wall were investigated to investigate the effect of the submerged wall on the flow velocity. In the five discharges, 40, 50, 60, 70, and 85 L/s, the velocity reduction was equal to 60, 55.2, 45.9, 37.5, and 29.4%, respectively. The effect of the separating wall in both submerged and non-submerged states on the water discharge rate was investigated. The results showed that the non-submersible barrier has gradually reduced the intake discharge in all discharges.