## 수치모델링을 이용한 측면 유입특성이 본류에 미치는 영향 조사

Mohammad Raze Raeisi Dehkordi^{1}*, Amir Hossein Yeganeh Mazhar^{1}

, Farzaneh Kheradzare^{2}^{1}– PhD. Student in the Department of Construction and Water Management, Science and Research Unit, Islamic Azad

University, Tehran, Iran^{2}– M.Sc. Graduate Water resource management, Department of Civil Engineering and Mechanics, Ghiaseddin Jamshid

Kashani University, Qazvin, Iran

- Corresponding author: mohamadreza.raeisi.d@gmail.com

## Keywords

Channel Confluence, Channel cross, sectional area, Cross channel angles, Modelling, Flow-3D

## Abstract

**Introduction**

One of the key issues in river engineering is analyzing the flow properties at the intersection of natural rivers and canals. The flow of the side channel moves away from the intersection of the two channels as a result of the exchange of input force from the side channel with the main flow after coming into contact with it. One of the most evident properties of the flow in these sections is the development of a revolving region with low pressure and even negative pressure close to the inner wall of the side channel. One advantage of the whirling flow in this low-pressure region is that it gives the flow enough space to sediment, but it also increases flow speed near the channel’s bottom and outside wall by lowering the inter*sectional area* of the flow. One of the most crucial considerations in the design of these intersections is minimizing sedimentation in the rotating region and scouring in the area above the shear plane.

**Materials and methods:**

The channel (flume) created in the laboratory based on Weber et al., (2001) model, was employed in the current investigation to confirm the validity and examine other study objectives. The main channel is 21. 95 meters long, while the side channel, which is at a 90-degree angle to the main channel, is 3. 66 meters long. The total downstream discharge is approximately 0. 17 m3/s, with the upstream velocities of the main channel being 0. 166 m/s and the side channel being 0. 5 m/s. In both channels, the flow depth and width are 0. 91 meters and 0. 296 meters, respectively. In this study, 6 various models’ angles of intersection between the main and side channels, inlet flow velocity, inter*sectional area*, and side channel length have been examined. Models 2 and 3 have intersection angles of 60 and 30 degrees, respectively, and share the rest of their attributes with the fundamental model, or model number 1. Model 1 is the same as Weber’s experimental model. The length of the side channel in model 4 is different from model 1. The only difference between model 6 and the basic model is the side channel intake speed.

**Results and Discussion**

Analyzing the intersection angle The angle between the main channel and the side channel is investigated in this section of the findings. Models 1, 2, and 3 are assessed using the intersection angles of 90, 60, and 30 degrees, respectively. In some studies, the impact of the intersection angle has been examined, but in this study, three-dimensional investigation in transverse and longitudinal sections as well as the plan of the intersection is discussed, as can be observed from the literature review. Considering three models with intersection angles of 90, 60, and 30 degrees, the kinetic energy contours at the channel’s middle height can be obtained for each model. The channel with a 30-degree intersection angle (model 3) has the maximum kinetic energy in the flow. The channel with a 60-degree intersection has the minimum kinetic energy. As a result of the maximum deviation of the flow in the main channel caused by the flow of the side channel, the channel with a 90-degree intersection also has the maximum kinetic energy near the wall in front of the side channel.

Examining the side channel length In model 1, the side channel is 3. 66 meters long, whereas in model 4, it is 5. 52 meters long. This study aims to determine how changing the side channel’s length affects the flow pattern where two channels intersect. The kinetic energy contours were obtained for two states of the channel length, which are known to extend the lateral channel, increase the energy of the flow after the intersection, and shorten the length of the high-kinetic energy zone. When compared to model 1 with a shorter length of the side channel, the width of the flow separation zone is reduced by approximately 20%, which results in less flow sedimentation. Figure 12 illustrates the rotating zones in the flow separation area. The flow separation region’s length is essentially unchanged. Studying the intersection of the lateral channel After determining the lateral channel’s length, its width and, consequently, its inter*sectional area* should be evaluated.

This section compares model 1 width of 0. 91 meters to model 5 width of 1. 40 meters. One of the most recent topics related to the intersection of the main and side channels is examining the intersection of the side channel. In model 5, the side channel’s flow rate has also increased due to an increase in the width or intersection of the channel. The flow rate through the intersection and the momentum of the flow from the side channel and the main channel increase when the side channel flow rate rises. The findings indicate that when flow width and side channel flow rise, energy increases after the inlet.

Investigating the value of inlet speed in the side channel Unlike the preceding sections, which were all concerned with the channel geometry, the inlet velocity in the side channel is one of the hydraulic parameters of the flow. In this section, models 1 and 6 with inlet velocities of the side channel of 0. 5 and 0. 75 m/s are evaluated. According to the modeling, the flow is somewhat horst before and immediately on the intersection of the flow level, but it undergoes a substantial prolapse just after the intersection. Model 6 has a larger volume and height of flow, but a smaller and softer prolapse after the intersection.

**Conclusion**

Some hydraulic and geometric properties of the intersection of channels have been examined using Flow-3D software. The RNG turbulence model was used for three-dimensional modeling. Some of the results are listed below. The flow is uniform upstream of the main and minor channels and only slightly becomes horst at the intersection. The analysis of the lengthening of the side channel revealed a 20% reduction in the separation zone’s width and a considerable reduction in the kinetic energy at the intersection. The input flow rate of this channel to the intersection increases with the speed and width of the side channel, which accounts for the local drop in the width of the main channel flow.

## References

- Azhdari, K., Talebi, Z. & Hosseini, S. H. (2020). Simulation of Subcritical Flow Distribution and Water Surface Fluctuations in Fourbranch Open Channel Junction with FLOW 3D. Irrigation and Drainage, 14(3), 1018- 1031. (In persian).
- Behdarvandi, M., Hajipour, M., Parsi, E. & Ansari ghojghar, M. (2022). Investigation of Velocity Changes in a Straight Asymmetric pattern at river bend. Water and Soil Conservation, 22(6), 81-89. (In Persian).
- Ghobadian, R. & Seyedi tabar, Z. (2016). Numerical investigating of the effect of lateral channel junction position on flow Rectangular Composite Channel Using Flow3D Software. Irrigation and Water Engineering, 13(1), 1-16. Doi: 10.22125/iwe.2022.158503 (In Persian).
- Burqaʻi, S. M. & Nazari, A. (2003). Laboratory investigation of sediment pattern at the intersection of channels. 6th International Civil Engineering Conference, Amirkabir University of Technology, Tehran, Iran (In Persian).
- Hemmati, M. & Aghazade-Soureh, T. (2018). Simulation of the Effect of Bed Discordance on Flow Pattern at the River Confluence by Flow-3D Model. Irrigation and Drainage, 11(5), 785-797.
- Hosseini, S, M. & Abrishami, J. (2018). OpenChannel Hydraulics. 35th Edition: Imam Reza International University, 613 pages (In Persian).
- Karami moghadam, M., Keshavarz, A. & Sabzevar, T. (2019). The Effect of Diversion Flow, Intake Inlet Shape, Topography and Bed Roughness on the Flow Separation Dimensions and Shear Stress at the Lateral Intake. Irrigation and Drainage Structures Engineering Research, 73(19), 113-126. (In Persian).
- Khosravinia, P., Hosseini, S.H. & Hosseinzadeh Dalir, A. (2018). Numerical analyzing of flow in open channel junction with effect of side slope of channel. Irrigation and Water Engineering, 10(1), 1-16. Doi: 10.22125/iwe.2019.95871 (In Persian).
- Kwanza, J.K., Kinyanjui, M. & Nkoroi, J.M. (2007). Modelling fluid flow in rectangular and trapezoidal open channels. Advances and Applications in Fluid Mechanics, 2(2), 149- 158.
- Masjedi, A. & Taeedi, A. (2011). Experimental Investigations of Effect Intake Angle on Discharge in Lateral Intakes in 180 Degree Bend. World Applied Sciences Journal, 15(10), 1442-1444
- Musavi Jahromi, S.M., & Goudarzizadeh, R. (2011). Numerical Simulation of 3D Flow Pattern at Open-Channel Junctions. Irrigation Sciences and Engineering, 34(2), 61-70 (In Persian).
- Nikpour, M. & Khosravinia, P. (2018). Numerical Simulation of Side Slope Effect of Main Channel Wall on Flow Behavior in Open Channels Junction. Irrigation and Drainage, 11(6), 1024-1037. (In persian).
- Raeisi Dehkordi, M. (2022). Description of types of pollution in water resources and protection of water resources, New Approaches in Civil Engineering, 6(1), 42- 52. Doi: 10.30469/jnace.2022.154373 (In Persian).
- Ramamurthy, A.S., Carballada, L.B. & Tran, D.M. (1988). Combining Open Channel Flow at Right Angled Junctions. Journal of hydraulic engineering, 114(12), 1449-1460.
- Tabesh, M. (2018). Advanced Modeling of Water Distribution Networks. 4th Edition: University of Tehran Press, 585 pages.
- Taylor, E. (1944). Flow Characteristics at Rectangular Open-Channel Junctions. Journal of hydraulic engineering, 10(6), 893- 902.
- Thiong’o, J.W. (2011). Investigations of fluid flows in open rectangular and triangular channels. Master’s thesis, Jomo Kenyatta University of Agriculture and Technology, Juja, Kenya.
- Weber, L.J., Schumate, E.D. & Mawer, N. (2001). Experiments on Flow at a 90° Open-Channel Junction. Journal of hydraulic engineering, 127(5), 340-350.