Background and Objectives: The Channels and rivers confluence phenomenon is the issue which occure in the irrigation and drainage Channels, superficial water accumulative Channels, water and waste water refinery and rivers. The aim of this research is to investigate the effect of several installed submerged vanes in tributary Channel on controlling and decreasing the erosion at 90 degrees confluence of Channels, detecting the best situation and vanes orders by using the simulation software. Materials and Methods: In this research, Flow-3D flow simulation software was used to model the various states of submerged vanes at 90-degree Channels confluence. In order to verify the results, the data from the experiments carried out in the laboratory of the civil engineering department of Sharif University of Technology have been used. The experimental model consists of a main Channel with a length of 12 meters and a width of 40 cm and a tributary Channel of 3 meters in length, the width of the tributary Channel is equal to the main Channel. The tributary Channel is located 6. 35 meters from the beginning of the main Channel and is connected to the main Channel at a 90-degree angle. The using equations were Navier-Stokes and continuity equations for modeling incompressible flows. For modeling turbulence, the k-w equation model was used. Results: The results of this study showed that software simulation can accurately estimate the scour pattern. So the difference between the maximum depth of scour of numerical and laboratory models in confluence was 1. 4%. Also few modeling were done with angles, dimensions and different locations of vanes to calculate the best conditions of vanes to decrease the depth of scour in Channels confluence. The results showed that it is possible to decrease the scour hole dimensions, considering that submerged vanes were installed in the 60 degree (in respect to longitudinal axis of Channel), the ratio of the length of the submerged vanes to the Channel width was equal to 0. 25, the longitudinal spacing of the submerged vanes was half the width of the Channel, the spacing of the submerged vanes from each other was 0. 375 of the Channel width and the distance between the installation of the submerged vanes from the intersection of 0. 25 to 0. 375 was the width of the Channel; submerged vanes effectively reduce the maximum depth of scour hole at the junction of two Channels with a 90 degree angle. Conclusion: The final result of this study shows that if submerged vanes are installed in an appropriate position with optimal dimension in the tributary Channel, they can reduce the maximum depth of the scour hole at Channel confluences. In this study, the maximum scour depth was reduced by 21% submerged vanes compared to the non submerged vanes.

Introduction: Streams typically have similar suites of Channel morphologies, with repeatable patterns of occurrence that have resulted in numerous classification efforts (Roper et al., 2008: 417-427). Recent approaches for river classification focus on watershed analysis related to land management and stream restoration, using a hierarchical approach that nests successive scales of physical and biological conditions and allows a more holistic understanding of basin processes (Shroder, 2013: 739). One of the most widely used hierarchical Channel classification systems was developed by Rosgen (Shroder, 2013: 742). In the current study, Gara Sou river Channel plan form are studied by using Rosgen geomorphological model in combination with HEC-RAS model.Materials and methods: This study is based on fieldworks and topographic maps of scale 1: 2000 (Ardabil Regional Water Authority). To determine the friction coefficient distribution of Channel and floodplain, land cover maps was generated using Google Earth satellite imagery. Rosgen (1985, 1994, and 1996) hierarchical system was used to analysis of river Channel morphology. The Rosgen system uses six morphological measurements for classifying a stream reach-entrenchment, width/depth ratio, sinuosity, number of Channels, slope, and bed material particle size. In this research, some of these parameters were calculated using HEC-RAS hydrodynamic model. For steady, gradually varied flow, the primary procedure for computing water surface profiles between cross-sections is called the direct step method. The basic computational procedure is based on the iterative solution of the energy equation. Given the flow and water surface elevation at one cross-section, the goal of the standard step method is to compute the water surface elevation at the adjacent cross-section. The flow data for HEC-RAS consists of flow regime, discharge information, initial conditions and boundary conditions (HEC, 2010).Results and discussion: According to calculations made in seven reach has been in class C and E, hierarchical model Rosgen. Gara Sou River in class C has a wider and shallower Channel and floodplain width significantly developed. Gara Sou River in class E also has a deep and narrow Channel (width to depth ratio) but floodplain width developed. In reach (1) floodplain width due to low geological control variable. In this reach was due to power of river, the bed river is cobble and gravel that leads to the river bed is in the Armoring range. With regard to slope variables and bed material, it is placed in the class C. in this class have a mean energy and high sediment load. Energy waste by meandering, bed forms (Pool- Riffle) and vegetation occurs. In the reaches of 2, 3, 4 and 5 width floodplain will be a significant development. In the reaches type of bed river is changed to gravel and sand and more of gravel and sand are. River slope in this reaches are between 0.02 and 0.039. In this reaches (2, 3, 4, and 5) river in the most part located class of C4b Rosgen model and only in some sections of the river have been E4b class. Average width to depth ratio is calculated 16.14 for the total reaches. In this reaches riparian vegetation are mostly dense shrubs that this high density of riparian vegetation plays an important role in the stability of the banks river in this reaches. In the end of reach (5) and reach (6) river slope between 0.001 and 0.02 is located and bed River is sand that often makes the river in this section in class C5 in hierarchical Rosgen model. Average width to depth ratio is calculated 15.46 for the total reaches. In reach (7) river slope to less than 0.001, but the bed river is still sand. According to the results, the major part of this reach is located class C5c and only in small portions cross sections of the E5 is placed class.Conclusion: In this study, Gara Sou River Channel was classified using geomorphological Rosgen model on the first and second levels. Despite the widespread use Rosgen model, has been criticized by some researchers. Problems with the use of the classification are encountered with identifying bank full dimensions, particularly in incising Channels and with the mixing of bed and bank sediment into a single population. Gara Sou River in parts of Type E has a low sediment supply, average potential bank erosion control and vegetation are very high. The rivers carry sediment are very efficient and river is low energy, loss of energy through the meandering, bed forms and vegetation occurs. Also this river in parts of the Type C has a high sediment supply, very high potential bank erosion control and vegetation is very high. In fact, vegetation combined with the bank erosion, determines the amount of lateral adjustment and sustainability of this river.

River morphology holds significant importance in the fields of geomorphology and river management and engineering. The marginal sections of rivers have consistently undergone changes in their riverbeds due to various social and economic factors. The Dare Ourt River, located in the Ardabil province, represents a permanent river that has experienced frequent floods and alterations in its Channel morphology in recent periods. In this study, the Dare Ourt river was thoroughly analyzed using the Rosegen model at levels one and two. To conduct this study effectively, detaied data such as 1:2000 river topographic maps, hydrometric data, and boundary conditions from the Ardabil Regional Water Authority were collected and utilized. Furthermore, the HEC-RAS hydrodynamic model was employed to extract the primary indices of the Rosegen model with greater accuracy. The outcomes revealed that the majority of the river sections exhibit a C6c type, characterized by an alluvial substrate. Additionally, other dominant types observed within the four examined ranges include B6c, E6b, F6, and D. Field visits also confirmed a transition in the river type from C to F within range 4, which presents challenges for the reconstruction and restoration of the river in type F. As a recommendation, it is advised to implement restrictions to prevent the river from transitioning into type F.

River confluence is an important element of river system. The entrance flow from the minor branch to the main Channel causes extensive variation in flow pattern which result a deep scour hole and formation of point bar. These phenomena can accelerate the rate of bank erosion, bring problems for navigation and may causes failure of the bridges or structure nearby. Despite of these, due to three dimensional structures of flow and sediment at river confluence, systematic study for understanding the mechanism of flow and sediments are very few. There for the main purpose of this study to conduct a comprehensive literature review and experimental program to study the effects of confluence angle on erosion and sedimentation pattern. To reach such goals first using the dimensional analysis, general non- dimensional equations were developed. Then many experimental tests were conducted for three confluence angles of 60, 75 and 90 degree and different hydraulic conditions. The experimental tests showed that as the confluence angle is increase, the scour hole and point bar dimensions increases. Using the experimental data, the effects of each non-dimensional parameters on scour hole depth were investigated and finally relations were developed for prediction the scour and point bar dimensions.

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 intersectional 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, intersectional 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 intersectional 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.

Using riprap is one of the common and economical methods for rivers bed protection against scouring. In this study, some stone sizes, under different hydraulic conditions have been tested to determine the criteria that affecting the stable size, of riprap at the threshold and failure conditions. In this investigation, it was found that in a constant flow ratio (Qr), with decreasing tail water depth and with increasing tail water velocity, the stability size of riprap was increased. Also it revealed that a constant size of riprap, with increasing flow ratio (Qr) in the threshold situation, tail water depth was increased and tail water velocity was decreased. At the constant size of riprap, with increasing total flow (Qt), in the threshold situation, tail water depth was increased and the stone with larger size will begin the incipient motion.

Flow characteristic at open Channel-junction (river confluence) have represented a major challenge for 3-D applications of CFD in last decades. Secondary flows not only will change the vertical profile of primary velocity but also will change scouring and sedimentation pattern at Channel- confluences. By present, with laboratory experimental test, field measurement and mathematic simulation the effect of discharge ratio, confluence angle and bed discordance carried out on 2-D or 3-D flow patterns. This research uses a 3-D program (SSIIM 2) for simulation the effect of tail water Froud Number (Frd) on flow pattern; especially secondary flow pattern at a 60 degree rectangular Channel confluence. The model uses a three-dimensional unstructured grid with a mixture of tetrahedral and hexahedral cells to model the geometry. The water flow is computed by solving the Navier-Stokes equations using k-e RNG turbulent model. The model was tested by comparing with two-dimensional velocity fields at confluence that have measured by Laser Doppler Velocimeter and water surface profile on a physical model. The result showed that with increasing tail water Froud Number, penetration of lateral flow into the main Channel decreased. The curvature of Lateral flow stream line when entrance to Channel- junction increases with increasing Frd; while the entrance angle of lateral flow decreases. Additionally, with increasing Frd secondary circulation that begins to performance just from location of downstream corner of junction became weaker. Also, secondary flow patterns and number of circulation cell will change strongly with moving to downstream and passing from separation zone. On the other hand, only one circulation cell of secondary flow is appeared, when Frd reduces. By moving downstream of confluence the center of this circulation cell change from top of water at right embankment toward the center of cross section

River confluence is a common feature of most irrigation and drainage Channels and river systems, where tributary conflicts the main Channel. In these section, rapid changes in velocity and discharge, sediment distribution and flow turbulent result in a deep confluence scour, a bar point in the separation zone at downstream of junction corner and finally vortex flow. Thus, the main goal of this study is to conduct a series of experimental tests to investigate the required size of rocks to control the scour hole. The results show that for a constant ratio discharge, Qr, the size of riprap in the incipient motion increases with decreasing in tailwarer depth. In other words, for any rock size the tailwater depth required for incipient motion increases with increasing the ratio of discharge, Qr. For each constant ratio discharge, or, the size of riprap in the incipient motion increases with increasing in tailwater velocity, Vt. Finally, some equations are presented for predicting the size of rocks and the proposed equations has been compared with existing ones.

In this article, an attempt has been made to estimate the amount of sound transmission loss in a flat oval Channel by applying the approach of statistical energy analysis. Correct estimation of sound transmission loss in an air conditioning Channel is of great importance due to the harmful effects of noise pollution in the environment on human health. Simulation with the statistical energy analysis method is a powerful approach to estimate sound and vibration in problems in which we deal with complex and multi-part systems; is considered. In this method, first, a system is divided into several subsystems, and then by writing a matrix equation that includes the energy exchanges between subsystems and energy loss coefficients; It is investigated from the perspective of vibration and sound estimation.On average, the model presented in this research is able to estimate the sound transmission loss in different dimensions of the air conditioning Channels according to the experimental results in the accuracy range of ± 2.5 dB. Considering that it seems that the results obtained from modeling with this method are in good agreement with the experimental data; The results of this research can be used as an efficient approach to estimate noise in oval shaped Channels stretched in different lengths.

There are some intersecting Channels which are seen during operation of open Channel networks (Irrigation networks, drainage, navigation, and… ). It is possible to produce some bed elevation difference during construction and/or because of some reasons such as inaccuracy in implementation, natural action or human made mistakes. In this paper impact of some factors such as discharge ratio, bed elevation difference ratio, erodible and non-erodible bed and bed material grading is experimentally investigated on scour depth in a 90º confluence. The straight Channel is 5m long and 30cm width and the intersecting Channel is 2. 5m long and 30cm width. After analyzing the results and comparing the topography when two Channels have elevation difference with the case in which two Channels have equal bed elevation, one can find that increasing the difference of bed elevation would result in scour depth increment by 78% while the same increment is less by 45% for the case in which the transverse Channel is not erodible. This can be because of a jet flow in the case of non-erodible. Also, increment of flow velocity in the produced steep bed in confluence in the case of erodible bed for both Channels, can increase the scouring hole depth.