flow pattern

Meanders in rivers are critical areas for studying flow patterns. Flow within river bends is influenced by centrifugal forces and pressure gradients. Given that rivers exhibit various bed slopes, studying the three-dimensional flow pattern in such channels is of significant importance. The objective of this study was to investigate the three-dimensional velocity components of flow in gentle and sharp 90-degree bends with sloped beds. Experiments were conducted in a channel with central curvature radius-to-width ratios of two, four, and six. Velocity measurements were performed using the Vectrino velocity meter, one of the most advanced instruments for measuring flow velocity. The results indicated that due to the effect of the water's weight component along the bed slope, the maximum longitudinal flow velocity in the initial sections of the bend for gentle bends occurs near the outer wall. However, in the later sections, it shifts closer to the middle of the channel width. Across all Froude numbers and all bends, the transverse velocity profile could be divided into two layers: one near the outer wall of the bend with maximum velocity and another near the inner wall of the bend with minimum velocity, located at 25% of the channel width. It was also observed that by doubling the Froude number from 0.05 to 0.1, the location of maximum shear stress extended from the range of up to 30 degrees to the range of up to 50 degrees of the bend section, and was concentrated near the outer wall.

Bridges are important for establishing communication routes, and every year many bridges are destroyed due to scouring around the support. Spur dike are hydraulic structures that reduce scouring by diverting streamlines from structures. In this paper, a triangular arrangement for permeable spur dikes is proposed, and its performance with linear spur dikes in controlling the scouring of the abutment is numerically investigated and compared. To make a correct comparison, the permeability ratio and the distance of both triangular and linear arrangements were assumed to be the same. The results show that the linear arrangement of three series of two columns performs better than the similar triangular arrangement, and the linear arrangement of four and five series of two columns performs worse than the similar triangular arrangement. Also, among all the models, the triangular arrangement equivalent to two series of five is the most optimal. It reduces scour depth by 46% compared to the control case (Abutment without protective spur dike).

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.

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.

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.

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.

The low inflow rate of water into the dam reservoirs causes sedimentation, leading to a decrease in the service life of dam. As a result, the performance of the dam in controlling floods and generating energy through water release downstream will be affected. Additionally, sediment deposition near the bottom outlets and turbines causes their burial, leading to difficulties in their operation and utilization. Installing inclined plates in the upper of bottom outlets is suggested as a new method to increase the amount of flushed sediments in pressurized flushing. Awareness of changes in the upstream flow pattern of the orifice is of great importance. In the present study, the effect of installing inclined plates on flow pattern changes in the upstream of the orifice was investigated using the Flow3D model. In this study, a numerical model calibration was performed using the results of experiments conducted in the hydraulic laboratory of the Faculty of Water and Environmental Engineering at Shahid Chamran University of Ahvaz, and the RNG turbulence model was chosen for conducting the simulation. The considered variables include plate width, plate installation angle, and plate installation distance to the orifice. In total, 5 scenarios (including the reference test (i.e., without installing plates)) have been defined for the numerical model.The results showed that the installation of inclined plates against the orifice led to the creation of vortexes and the development of a low-pressure zone, resulting in an increase in the volume of flushed sediment. Also, reducing the width of plates, increasing the installation angle, and increasing the installation distance of the plates will lead to a decrease in the intensity of eddies and a decrease in the range of low-pressure zone, which reduces the effect of installing inclined plates to increase flushed sediment volume.Based on previous studies, the amount of sediment output in pressurized flushing is limited and confined to the vicinity of the dam body. Therefore, this method is not used to revive the dead storage capacity of the dam reservoirs. Ancillary facilities such as bottom outlets and hydro-power plant outlets are located near the dam structure, and sediment entry into these facilities can have destructive effects. Therefore, providing methods to increase sediment discharge from near the dam body can be highly beneficial. Additionally, by creating a low-pressure zone in the upstream of the outlet, a suction effect is created, which can be useful in increasing the volume of sediment discharged during turbidity current discharging from the bottom outlet.

Pre-sedimentation basins are considered as the major and important components in water treatment process through conventional method. Because of the high cost of constructing these basins, which is approximately 30% of the total costs of water treatment plants, modeling and optimum performance of pre-sedimentation basins are very important. In pre-sedimentation basins, because of the existence of velocity gradients, secondary and rotational flows occur. In order to increase the performance of a pre-sedimentation basin (clarifier), it is essential to have a uniform and calm flow field. The use of suitable baffle configurations may help forming favorable flow field and increase the efficiency of the pre-sedimentation basins. In order to find the proper position of a baffle in a rectangular sedimentation basin, computational investigations are performed. The first step to optimize pre-sedimentation basin is accurate calculation of the velocity field and the volume of rotation zones. Flow guiding blades can also be used to depreciate the inlet jet and reduce turbulent kinetic energy. Because of the flow complexity and also the effects of scale, physical models can not solely provide a clear understanding of the physics governing the flow field and it is necessary to study this phenomenon numerically along with field and experimental studies. The first step to optimize pre-sedimentation basins is accurate simulation of the velocity field and the volume of rotation zones. In the present study, numerical simulation of flow was investigated in a pre-sedimentation basin using SSIIM and Fluent models. Continuity and momentum equations were solved using finite volume method. Flow analysis was done steady by the SIMPLE algorithm for velocity and pressure coupling. Discrete method of continuity equations, momentum, turbulent kinetic energy, Reynolds stress drop and discretion of pressure equation are standard. The numerical results were calibrated with experimental results of Shahrokhi et al. (2011) and Imam et al. (1984). Flow simulation was performed in 3D and flow velocity profiles were compared with the experimental results in different sections of a pre-sedimentation basin. Then, in order to sedimentation investigation in the pre-sedimentation basin, advection and dispersion equation of sediment concentration was solved simultaneously with the governing equations of flow. The results of the vertical distribution of sediment concentration profiles in different sections of the basin were compared with the experimental and numerical results of other researchers. Finally, the effect of flow guiding blades on the flow pattern and the efficiency of sedimentation in the pre-sedimentation ponds were investigated. The comparison showed that there is a good agreement between numerical and experimental study with an average error of 6%. Flow rate is one of the effective parameters on creating a rotational zone inside the basins. With increasing the inlet flow rate from 0.002 to 0.01 cubic meters per second, the length of the rotational zone has increased 25% and the width of the rotating zone has increased 45%. The secondary and rotational currents formed at the entrance of the basin are two small rotational zones and approaching the middle of the basin and formation of flow separation zones, the number of rotating areas and their dimensions have increased. From the beginning to the middle of the basin, the shear stress is increased. In the sections x = 0.46 m and x = 0.82 m, the amount of shear stress is maximum. Amount of energy in the middle of the depth has decreased by 40% compared to the water level and about 60% compared to the floor of the sedimentation basin. It showed that there is a good agreement between the numerical and experimental results. It also indicated high ability of SSIIM in predicting distribution of sediment concentration profiles in pre-sedimentation basins. With increasing flow depth, the sediment concentration decreases. In the section x = 1.58 m, the sediment concentration near the free surface is 44 mg L-1, which decreased by 57.48% compared to the concentration of sediment in the basin bed. In the case without the guide blade, near the free surface of the stream, the sediment concentration was decreased. Also, in the middle of the basin, due to the turbulence of the flow and the rotational areas, the secondary current strength was maximal and decreased as it approached the end of the basin.

With the advancement of science, human societies use transmission pipes to transport water and other fluids from the bed of seas, rivers, streams and natural drains. If pipelines pass through rivers and seabeds on their way, great care must be taken in their design. The main purpose of this study is to investigate the effect of the insertion depth of the shield on the pipeline scour at different distances of the pipe from the bed. This study was carried out in a flume with the length of 10 m and the width of 30 cm. Experiments were conducted under clear water condition (u/uc=0.95). Uniform sediment with a median diameter of one millimeter (D50=1 mm) was considered. In this research, a PVC pipe with an external diameter of 2.5 cm was used. The distance of the pipe from the bed (G) was considered based on a coefficient of the pipe diameter (0, 0.25, 0.5, 0.75, 1). Also, the insertion depth of the shield (Dw) was selected according to a coefficient of the pipe diameter (0, 0.25, 0.5, 0.75, 1, 1.25, 1.5, 1.75 and 2). The results of the experiments showed that in the case that the shield was not used, with the increase in the distance between the pipe and the bed, the maximum scour depth under the pipeline decreases.

One of the structures that is widely used for training the rivers and channels is groyne. From past time, application of the groyne indicates the wide advantages of these kind of structures. One of the important issues in the design of groynes is the local scour phenomenon in the nose due to changes in flow pattern and presence of strong vortices. In recent years, most research has been based on open and impermeable groynes, and most have been done in laboratory. Therefore, in this study, the scour and 3D flow pattern around the T-shaped gabion groyne were simulated using Flow-3D numerical model and turbulence model (k-ω) and compared with the experimental results. The results showed that the model (k-ω) has better agreement with the experimental results in predicting the maximum scour depth and flow pattern around the T-shaped gabion groyne. So that the location of scour and the maximum depth of scour obtained from numerical simulation are close to the experimental results. Increasing the body permeability also has a significant effect on reducing turbulence, eddy and transverse velocity.

The construction of structures such as gutters, despite erosion control, can be  due to the formation of a localized flow structure such as sudden expansion and contraction at the flow passage, the formation of downstream flow, and its impact on the channel bed upstream of the gutter and The shear layer and the resulting turbulence can cause local erosion and threat to the structure. In this research, using the two-dimensional numerical model SRH-2D, the flow pattern around the spur dike wall was simulated with angles of 45, 90, and 135 degrees in the channel. The results showed that with an angle of 45 degrees, the length of the return zone of the stream will be about 2 and 8 times shorter than the 90 and 135° angle, respectively. However, in a spur dike with a 90 degree angle, the length of the return zone is about 3.5 times shorter than when the breaker is located at an angle of 135 degrees in the channel. Also, shear stress in the areas close to the floor in the spur dike with an angle of 45 degrees is the lowest value and the breaker with an angle of 135 degrees has the highest value.

The construction of hydraulic structures such as bridge piers in river beds changes the hydrodynamics of the flow and is associated with the scouring phenomenon. This process has been investigated by many researchers with numerical and laboratory methods. The implementation of scouring reduction measures has also been considered in addition to investigating this phenomenon, due to the destructive changes of scouring on the morphology and the river bed shape. In general, these measures are divided into two general categories, direct and indirect, which the use of submerged vanes is one of these reduction measures. Based on less attention to this scour reduction measure; in this study, the effect of a group of two submerged vanes on reducing scour around the cylindrical bridge pier with a numerical approach of the FLOW-3D model is investigated. Dimensional analysis showed that the position angle of the vanes, the location, and the height of the vanes are effective parameters. According to the results, the installation of submerged vanes in all cases reduces scour and the position angle of 30 degrees, in location 0D,1D,2D, and the height of the vanes equal to the sedimentary bed leads to the greatest reduction of scour.

In this research, the flow-3d numerical model has been utilized to analyze the scouring phenomenon around the cylindrical bridge pier. In order to validate the numerical model, first, the sensitivity of the mesh dimensions was performed and the 8.5 mm mesh size was selected. Then the analysis of the geometric model for the bridge pier was conducted with different turbulence models k-ε, k-ε RNG, and LES, and the numerical results were compared with experimental data. It was found that the numerical results of the LES model are the most consistent with the experimental data, so this turbulence model has been used for the conditions of bridge pier with submerged vanes. Different times for scour hole development were investigated to determine the processing time of the numerical model and the computational cost, and finally, it was observed that the scour equilibrium time of 500 seconds is suitable for numerical analysis, and after this time the maximum scour values remain almost constant.

By increasing the position angle of the two submerged vanes up to 30 degrees, the amount of scour depth decreases. But by increasing it by 30 degrees, this trend decreases and does not follow a specific trend. The most suitable position of the group of two submerged vanes is in 0D,1D,2D location, and the location of 2D,3D,4D has the least effect, which reduces the distance between the vanes from the upstream of the channel to the bridge pier, the separation point of boundary layer moves to the bridge pier, thus reducing the thickness of the boundary layer. Therefore, by reducing the distance between the vanes and the bridge pier, the intensity of shear stress to dig bed sediments around the bridge pier is reduced and as a result, the effect of submerged vanes and their protection from erodible bed against scouring phenomenon increases. It was found that the presence of submerged vanes in all cases reduces the maximum scour depth, but this amount of reduction is not the same due to the different positions of the vanes. Observing the flow pattern, it can be concluded that the velocity upstream of the pier is negative and rotational flows are formed in this region, which are the horseshoe vortices that are one of the reasons for the formation of scouring holes.

In all cases of installation of submerged vanes before bridge pier, scour depth was reduced because the presence of vanes caused local scouring around the vane itself and the washed sediment particles were transported by the flow to the scour hole created upstream around the bridge pier. On the other hand, in all locations, by increasing the position angle of the two submerged vanes, the transverse area is more affected by the two vanes, and a stronger drag force is applied to them. In other words, the resistance to current increases, the flow moves away from the bridge pier, and also fewer bed particles are transported around the bridge pier. As the height of the vanes increases, the intensity of the flow colliding with the vanes increases, and as a result, the amount of scouring depth upstream of the vanes increases, and despite the reduction of scouring upstream of the bridge pier, the performance of these vanes decreases.

Embayment or Side-cavities are built as a natural or artificial complication, which generally has shallow flow conditions, as affecting the hydraulic conditions of the flow. These complications affect important hydrodynamic processes that play an important role in the general behavior of the flow by creating secondary structures and shear layers. Therefore, the experiments were performed in an Embayment with a size of 0.3 * 0.3 m, adjacent to a canal 0.5 m wide. Speed measurements in the defined network were performed using the Vectrino 3D Velocimeter. Observational results confirmed the existence of a large-scale gyre in the interior of the embayment. Further analysis of the data showed that the velocity in different directions is affected by flow of the main canal and with increasing current in the main canal flow, the velocity in the embayment also increases. Also, the results showed that at a constant flow through the main channel, with increasing flow depth, the speed in the outer half of the embayment decreases as the main channel but in the inner half, the speed increases with increasing depth. This indicates as increasing depth, a greater advancing of the stream into the embayment would be observed.

One of the complicated phenomena in sediment hydraulic engineering is scouring around bridge pier. Regard to three-dimensional and complicated flow pattern around piers, measuring some hydraulics parameters during the tests such as flow pattern, variation of bed profile and shear stress are difficult, in this situation application of numerical models in order to extract results and more detailed study is useful. Aim of this research is numerical modeling of flow pattern, variation of bed profile and scour depth and shear stress around rectangular pier using Flow 3D and applying the results to protect piers against scouring. Results showed, for aligned pier with flow, shape of scour hole and flow pattern were symmetrical, the side in contact with flow is high-pressure and the other side is low-pressure. As increase of pier angle, shear stress in front of the pier increased so that for pier with 10° angle with flow direction, shear stress was 0.55 N/m2. Also fluctuations of bed profile and water surface increased. Application of submerged vanes, changed scour pattern and moved sediment in front of pier which scouring was reduced. Increase of height and angle of submerged vanes improved their protective role. Base on the results of numerical model, after 30 minutes, scour depth in front of pier in aligned pier with flow and angle of submerged vanes 30°, in same level with bed, 1.25 cm and 2.5 cm on the bed, was 3.1 cm, 0.035 cm and +0.005 cm (on the bed), respectively. As increase of pier angle, performance of submerged vanes to control scouring in front of pier and in side of high-pressure wall decreased, but in side of low-pressure wall scouring compared with alone pier was less.

Studying and recognizing the flow dynamics at the junction and downstream of the junction is essential in designing the stable geometry of prismatic canals and providing a suitable protection solution for river systems. According to field data, the existence of different junction angles and bed discordance between the main and tributary canals is one of the most common physical characteristics of the most natural junction. The present research aims to numerically investigate the effect of main canal cross-section shapes (rectangular and trapezoidal) and junction angles (45° and 90°) on flow dynamics at river junctions of the concordance and discordance bed level. The results showed at the concordance bed level and junction with a  angle, in both cross-section shapes, the flow separation zone is formed near the bed, with the difference that in a trapezoidal section, its dimension was bigger than the rectangular section. At the  angle of the concordance bed level, this zone did not appear in any sections; but for unequal bed level junction, the separation zone was formed only on the water surface and for the trapezoidal section. In addition, the flow separation zone was not formed at the  discordance junction near the bed, but at the water surface its dimension in trapezoidal shape was more than the rectangular. Besides, the backwater at the upstream of the junction in main canal decreased in trapezoidal shape and in  junction angle.

One of the important aspects in describing river behavior is its curvature. The production of successive bends in natural rivers is an inevitable component of the process through which the river changes. Understanding the flow behavior in the interaction between the main channel and the floodplain, especially during floods, is necessary to protect soil and water structures. This study was conducted to better understand the hydrodynamics of the middle and turbulent flow in compound meandering channels. According to the natural conditions of most rivers, due to variation of discharge and depth ratios (flow depth in floodplain to flow depth in the main channel), in this study, a rectangular meander laboratory channel with a constant sinuosity 1.3 for different depth ratios of 0.35 and 0.55 was investigated. The results showed that the size of velocity components (u,v,w) at 0.35 relative depth was greater than 0.55, which  indicating higher vortex strength and interaction intensity between the main channel and floodplain at lower relative depth. Also, by investigating the secondary flows, the existence of clockwise and counterclockwise rotational eddy currents in the main channel and floodplains and the location of these currents were determined.

Side weirs are installed on the side wall of main channels. By reaching the flow to the side weir, the exceeded flow falls from the side weir crest and is directs to the side channel. The flow within the channels with side weirs is considered as spatially varied flow. In this study, the three-dimensional flow in a rectangular channel with side weir was simulated by the FLOW-3D software. For simulating the turbulence of the flow, the standard and RNG turbulence models were used. According to the modeling results, the accuracy of the RNG turbulence model was higher than that of the standard model. Furthermore, the Volume of Fluid (VOF) model was used for estimating the variations of the flow free surface. In the study, the velocity was predicted with an acceptable accuracy. Also, the MARE values for the longitudinal, transverse and vertical components were estimated 0.480, 0.468 and 3.519 percent, respectively. Then, the effects of sharp and broad crested weirs on the characteristics of the flow field in the main channel along the side weir for three different models with width of 0.01, 0.05 and 0.15 m were investigated. According to the numerical modeling results, by increasing the width of the side weir crest the shear stress value in the vicinity of the side weir crest increase significantly.

In recent years, Lake Urmia has encountered with environmental crisis, due to poor management of water resources, increasing the agricultural land and over the construction of dams on feeding rivers. In this research, a 3D model (Mike 3 flow model FM) was applied to investigate the effects of changes in wind direction and construction of causeway on flow circulation and salinity distribution in Lake Urmia. The salinity data measured in two depths (near the water surface and close to the bed), and different locations were used to evaluate the calibration and verification of the model. The results of the present study showed that the wind speed and its direction are one of the important parameters that play a major role in flow circulation patterns, especially in the surface layer of the water, and salinity distribution in both cases with and without causeway. Moreover, three-dimensional simulation results revealed that the flow path and salinity distribution were different in surface and bottom layers, due to the wind direction and construction of the causeway.

Reducing scouring is inevitable to prevent the destruction of hydraulic structures on the water flows. In this research, the effect of semicircular collar on the reduction of scour depth around the abutment was investigated with the aim of identifying the flow pattern changes around this structure. Experiments were carried out under clear water conditions. Semicircular collars were examined on semicircular abutments in two sizes 1.5L and 2L (L is abutment length against the flow) and at three different levels relative to the bed; bed alignment, 0.2L below and 0.2 above the bed. The results showed that the existence of the collar, in addition to reducing the final scour depth, caused a delay in the scouring process. This effect has also been increased by increasing the size of the collar. In addition, the position of collars with the same size can improve collar performance and efficiency on the design cost. Based on the results of the experiments, the collar with 2L size and under the bed showed better performance and reduced the final scour depth by 58% compared to the control abutment. Also, according to the experiments, the position of the collar under the bed showed better performance. By investigating the flow pattern around the abutment in conditions with and without collar, it was found that the collar reduces the flow velocity in different directions, especially in the upstream of the abutment. Also, its effect on downflow reduces the strength of the vortices and changes the reciprocating behavior and displacement of the vortices. So that the presence of collar has reduced the maximum downflow velocity at the upstream abutment by 39%.

Generally, intakes are used for conveying and diverting the flow within main channels and rivers. In this study, a flow field was simulated using FLOW-3D software. In addition, the flow free-surface variations were predicted using the Volume of Fluid (VOF) scheme. The flow turbulence was estimated by standard k-ε and RNG k-ε turbulence models. For instance, the MAE values for standard k-ε and RNG k-ε models to simulate the free surface profile were computed 0.166 and 0.201, respectively. The modeling results showed that the numerical model simulated the flow field with an acceptable accuracy. For example, the RMSE, MAE and R values for the simulated flow free-surface variations were calculated 0.164, 0.158 and 0.997 percent, respectively. Then, the effects of four flow division angles (30, 45, 75 and 90 degrees) on flow field pattern were considered. Regarding the modeling results, the highest depth-averaged velocity was obtained for the model with 45-degree. Among the models with division angles of 30, 45 and 75 degrees, the maximum shear stress was predicted for the model with 45-degree.

The erosion of riverbeds is one of the factors that causes changes in the morphology of rivers. Scour depth represents the amount of potential degradation of the flow around hydraulic structures located in the flow path. Therefore, it is necessary to determine the scour depth and flow rate. In this study, the experimental results of bed topography changes and flow patterns around impermeable and impermeable groines are compared. For permeable groines, two types of gabion groines and one and two-row groines with a 90 degree angle to the flow were used. In the use of two-row groine, the two positions are considered parallel and zigzag. Experiments were performed in a rectangular channel with a moving bed of 60 cm width and a flow rate of 28 lit/s and Froude number of 0.26. The results showed that the trend of maximum scour depth change with increasing permeability decreased. The scour depth in gabion groines is much higher than rod groines with the same permeability. Also, the effect of increasing the row spacing of two-row groines on the prediction of the maximum scour depth for the zigzag type is additive and for the parallel type it is decreasing.

In this paper, the physics of passed flow on submerged vane that placed at the bottom of different kinds of channels is studied. Also it presente the effects of: changing angle’s vane, the distance of vane from wall and the situation of vane in front of the lateral intake on the physics passed flow on submerged vane. In this order we use the fluent software to simulation flow pattern around the submerged vane at the bottom of straight channel, U shape channel and U shape channel whit lateral intake. The results show that when the vane placed at the bottom of the straight channel with angle of 20 degree 2 vortex by same direction at both side of the vane is created. By changing the vans angle from 20 to 40 degree, one smaller vortex with opposite direction near the bottom and close the trialing edge is created. This vortex is horseshoe vortex. By using vane in U shape channel, the vortex’s direction which is created by the vane,become greater than past. This subject show that workability of the vane in U shape channel is better than in straight channel. Horseshoe vortex’s formation close the trialing edge depends on the high angle of attack. In U shape channel with lateral intake vortex is smaller because of the suction that is made by lateral intake.

In general, rivers are one of the best and most accessible water resources at the disposal of mankind.  So, given the effect of the force of water and changes on the  flow patterns and consequently, on river morphology changes, the analysis of the flow in the river is important and necessary to organize projects, flood control and water supply structures downstream. In this study, by using numerical models CCHE2D hydraulic conditions Dimeh River Bridge between Oregon Bridge Sudjan was investigated. CCHE Model is a mathematical model capable of simulating the flow patterns and sediment transport in rivers and canals laboratory network. The numerical model in 1998, based on the calculations by the National Centre for Water Science and Engineering, University of Mississippi (NCCHE), was developed and has been applied in many research projects related to water engineering. At the outset, the input data required model provides and numerical model was implemented. In the next step, the results of the model were calibrated and validated using field data measurements; eventually, they were extracted and their model results were compared; it was confirmed that CCHE model could still simulate the flow pattern.