In this paper, scour profiles downstream of adverse stilling basins, due to the submerged jet issuing from a sluice gate, were investigated. Experiments were conducted in a wide range of sediment sizes, incoming flow Froude numbers, tail water depths, length and slope of the stilling basin. The results showed that the scour profiles at any bed slope are similar in shape. However, the longitude evolution of scour profiles and the volume of eroded materials increased in accordance with the slope of the basin. It was observed that the maximum depth of the scour hole occurs in the vicinity of the side walls and slightly decreases towards the centerline. A polynomial equation was derived to describe the nondimensional scour profiles at different slopes. Based on experimental data, the scour characteristics have been correlated with the time of equilibrium stage by developing some empirical relationships. Finally, a power-law equation was derived and fully defined to include the dimensions of the scour hole time scale and the geometry of the sluice gate.

In this paper, the geometrical similarity of scour holes downstream of a sluice gate is studied experimentally. Although, nowadays a comprehensive understanding on scour of noncohesive sediments is attained, because of the complex nature of clay minerals, the scour of cohesive sediments has received less attention. 36 experiments with 12 hours run time, was carried out in a rectangular flume of 9 m length, 0.6 m height and 0.5 m width. Six mixtures of cohesive and noncohesive sediments with different fractions of clay minerals ranging from 10 to 40 percent were tested. The results show that the scour profiles are nonuniform across the flume width. Despite the noncohesive sediments, the scour hole in cohesive beds could not be introduced as a unique equation. Therefore, three different types of scour holes are distinguished and in each case, graphs and equations are presented to determine the shape of the hole. Also, a novel equation is proposed to calculate Bw parameter which is used to nondimensionalize the scour hole. Finally, the effect of tailwater depth is investigated.

Background and Objectives: One of the new methods for controlling erosion on the outer bank of river curve is the use of plates connected to the riverbank. Coastal vanes are the environmental structures which are used to control bank erosion, divert flow from bank to river center, improve sediment transport status, develop river for sailing, restorate and develop river's aquatic habitat. Despite the many advantages of coastal vanes, there is no detailed information about erosion and sedimentation and flow patterns around them under different hydraulic and geometric conditions and fewer research have been done. In the present study, the effect of different installation scenarios of triangular permeable vanes on bed sediment longitudinal and transverse profile changes in a laboratory channel with a 180-degree bend is evaluated. Methods: In this research, the main purpose is to investigate sedimentation and erosion patterns in the rivers’,bend using coastal triangular vanes,in this regard, the impact of distance between triangular vanes, their effective length, and Froud number on the erosion control of the outer bank of the 180 degree bend is focused. Experiments in a laboratory flume with a mild 180-degree bend with a ,,3,B R ratio and a rectangular cross section with a width of 0. 6 meters is done. The angle of fixed triangular vanes is 60 degrees, the height of the permeable triangular vanes from the sediment surface is 10cm and the permeability of the triangular vanes is 12%. The experiments were carried out with limpid water mode. The effective lengths of the prepared vanes were 12, 15 and 20 cm with installation intervals of 60, 75 and 100 cm respectively and were run at two different inlet discharges. Results: Investigating the effect of the distance between permeable triangular vanes on bed topography shows that in each Froud number, with increasing the distance of vanes from each other, the maximum scour depth will be increased. The results demonstrate the use of permeable triangular vanes causes the flow deviation from the outer bank to the center and then the inner bank of the flume, which leads to control the erosion in the river outer bank. By increasing the inlet flow discharge and increasing the effective length of triangular vanes and the distance of triangular vanes from each other in a 180-degree bend, the maximum scour depth and volume are increased. The installation of triangular vanes with an effective length of , W 12cm,5 ,and a distance of 5L causes the flow deviation from the outer bank to the vanes cape and the middle of the flume, consequently results in a decrease in the shear stress in the middle of the flume and scour depth of the erosion channel and creates thalweg in the vanes cape. Conclusion: The results illustrate that by installing the triangular vanes, the point-bars are created in the interval between them. Therefore, during the effective length of 12cm, the maximum height of the point-bar on the outer bank equals to 30 and 31% of water depth, between the 0 to 170 degrees and 68. 7 to 115 degrees equal to 11 times and 3 times the distance between the vanes, for discharge values of 13. 5 and 15. 5 l/sec, respectively. Also, for the mentioned conditions the width of the point-bar on the outer bank reaches 85% and 75% of vanes’,effective length, respectively. Permeable triangular vanes with six pillars are recommended for meandering rivers like Karun in 90 and 180-degree arcs. These rivers have high torsion and curvature as well as high flow depth and low flow velocity in them, which contain high suspended sediments and the slope of this type of rivers is 0. 001 or less and due to the low slope, their sediment carrying potential. Sediment loads are mostly fine.

Among the issues related to bridges distraction, a flood which causes scouring has been known as the main reason of bridges destruction. Therefore, finding an effective solution is vital for decreasing scouring depth. In this study, the effects of local roughness elements with different distance were investigated for a semicircular abutment under clear water scouring condition. Results showed that existence of roughness reduced the scouring process and reduced the final scour depth by 47%. There was a significant relationship between roughnesses function and the distance between them. So that the existence of an optimal value for the distance between the roughnesses increased the roughness function and decreased the scouring process. In addition, the study of vertical velocity profiles revealed that existence of positive vertical velocity in the hole located at upstream of the abutment and also negative velocities at higher depths were the indicator of downflows. As a result, these downflows lead to the formation of powerful vortexes inside the scouring hole and in front of the abutment. Comparison of the flow profile around the roughened abutment with the control abutment showed that velocity of downflow is significantly reduced for abutment with roughness. Moreover, the depth of scouring hole was reduced at behind of the abutment, due to the impact of roughness on vertical velocity profiles at downstream of abutment. So that, the velocity reduction of the vertical flow in the front and behind of the roughened abutment was to 0. 13 U and 0. 4 U (U approaching flow velocity), respectively.

Scouring is one of the issues that is important in the design of various types of hydraulic structures. One of these structures is a stepped spillway. The aim of this study is to evaluate the similarity between the profiles of scour holes downstream of the stepped spillway. To do so, results of 67 experiments in two different experimental models were used; these results were in a wide range of particle Froude number, the stilling basin length, downstream depth, sediment particle size distribution and two different slopes of stepped spillway. In this study, 5 different lengths of stilling basin, from 37 cm to 120 cm, were used. Also, the range of utilized discharge was from 8.43 lit/s to 88.95 lit/s. Duration of the tests were selected to be 6-hours, 8 hours, 12 hours and 24 hours and, in total, 834 scour profiles and approximately 85000 points to were used derive required relations and to perform other analyzes. Based on the experiments results, the similarity between scour-holes located in downstream of stepped spillway was analyzed. In this process, two methods were used to make the profiles dimensionless. Based on statistical parameters, best method was selected and similarity of downstream profiles were shown. Relations that predict maximum scour depth, the distance from maximum depth to the end of the stilling basin and volume of transported sediments are developed based on the dimensionless parameters in different time periods. Furthermore, impact of different parameters on the geometry of scour holes were studied. When the Froude number increases, while all other parameters are constant, the dimensions of the scour-hole increases. When the stepped spillway slope increases, the dimensions of the scour-hole decreases and, moreover, when the tail water depth increases, while all other parameters are constant, a deeper hole with longer longitudinal distance forms. Overall, 8 cross section profiles under different conditions were taken. These profiles indicate transverse development of the scour-hole, in addition to longitudinal development.

When depth of flow past a river bridge exceeds opening under the bridge, the flow under the bridge becomes pressurized. The water is directed downward and under the bridge deck, causing increase in velocity and shear stress on the bed thereby increasing bed scour. This is termed as Pressure Flow Scour. The present study investigates the phenomenon of pressure flow scour resulting from a submerged bridge deck over an unprotected erodible bed. Velocity of approaching flow, depth of flow, degree of submergence and width of bridge are some of the parameters that are likely to affect the scour under a submerged bridge. The effect of fluctuations in the flow depth on the depth of scour increases with decrease in constriction. The experimental data of Edward et al. (1) has been merged with the present study and a conceptual relation is developed between scour depth and degree of submergence in the form of scour fraction and constriction ratio. For incipient flow conditions on the upstream of a submerged bridge, the final clearance under the bridge is equal to the depth of approaching flow. The study has been extended to include effect of unsteady flow in the form of a hydrograph, Interference of two similar submerged bridges, Interference of a submerged bridge with an un-submerged pier and a submerged bridge in conjunction with a circular bridge pier.

One of the common methods of river improvement and bank protection is using spur dikes. Building spur dikes makes the flow path to be modified. Concentrating the flow in the middle part of the river causes the river side not to be washed out. The new flow path makes the river bed next to the end of the spur dikes to be washed out. Usually the spur dikes are built in group because of extending the protected zone. The stability of these spur dikes against the river flow depends on stability of the first spur dike. The purpose of this laboratory research is to investigate different ways for reduction of erosion in the first spur dike. It is suggested to use a shorter (minor) spur dike at the upstream part perpendicular to the flow direction. Aim in this research , it is intended to find the optimum distance between shorter spur dike and first spur dike in order to have minimum erosion in the first spur dike. From the hydraulics point of view, L’/L (the length of shorter spur dike to the length of first spur dike ), X/L (the distance between first spur dike and shorter spur dike to the length of first spur dike) and Froude number has been studied and results has been presented in the form of equations.

In this research, the dynamics of local scour processes is studied in the context of the erosion that takes place downstream from a submerged sluice gate. The most important factors, which affect the local scour processes downstream of the sluice gate are identified and grouped by dimensional analysis to obtain the dimensionless parameters. Experiments were carried out in a horizontal rectangular flume of 9 m long, 0.5 m wide and 0.6 m height. Two gradations of uniform non-cohesive bed material were used for various tailwater depths and flow rate conditions. A total of 22 tests were carried out, each for a period of 12 h. An equilibrium scour condition was not attained over this time period for any of the tests, although a similarity in the bed profiles is observed in the region close to the rigid apron. Based on the experimental data, new dimensionless equations and graphs are presented to determine the shape and dimensions of characteristic lengths of scour hole such as maximum depth of hole and its position, brink scour depth, maximum extension of whole, dune height and its distance from the end of apron. Also, the results are compared with previous researches.

Stilling basins are used in the outlet of channels, chutes and culverts to dissipate the excess kinetic energy of incoming flow. One of the basins in which the energy of incoming flow is dissipated by impact, is USBR VI stilling basin. The USBR VI stilling basin was first introduced by Bradely and Peterka in 1995 and then was modified by Biechley in 1978. This structure consists of a middle wall and an endsill. Scouring around the structures that are located in the vicinity of erodible beds, such as stilling basins, has always been one of the most important problems related to these structures. Unlike other types of stilling basins, the studies carried out around this type of basin are limited, and there are still many hydraulics features of this type that have not been considered in previous researches. In this article, the effect of the shape of endsill on scour depth downstream of stilling basin is evaluated. Based on Beichley graph (Standard Design), the physical model of stilling basin was designed, constructed and installed in the hydraulic laboratory of Tarbiat Modares. Experiments were conducted in a 0.8 m wide, 0.9 m height, and 0.8 m length rectangular channel. The pump used in the experiments had a nominal flow rate of 400 cubic meters per hour (about 120 liters per hour), a head of 11.7 meters, a power of 22 horsepower, and an engine speed of 1450 rpm. In the design of experiments, the parameters including approach Froude number (i.e. 1, 1.5 and 2 times of standard Froude number on Beichley graph), the diameter of inlet pipe (i.e. De = 5, 8, and 12 centimeters), and endsill shapes (triangular, stepped and circular quadrant), in the form of 27 tests were assessed to study the dimensions of the scour depth. The observations revealed that in all three endsill shapes, the increase in Froud number has led to the decrease in scour index. the circular quadrant endsill had the lowest scour depth in the front of endsill and the least scour index, in the range of the Froude number of 2 to 6. In the range of the Froude numbers of 9 to 14, the triangular endsill causes the lowest scour index. In the relative diameter of inlet pipe equals to 10.16, for Froud numbers equal to 9.27 and 13.91, the triangular shaped endsill has the least scour index. in every endsills, decreasing the pipe’s diameter results in the maximum depth of the scour. Another important finding is that sediment bar is only formed in experiments conducted with inlet pipe’s diameter equal to 5cm for Froude number equal to Froude number on Beichley graph. The biggest amounts of the height of sediment bar and maximum scour depth are found for the stepped endsill and the smallest amounts of the height of sediment bar and maximum scour depth are found for the circular quadrant endsill. Subsequently, the non-dimensional equations according to the Froud number of incoming flow and the relative diameter of inlet pipe, were presented to estimate the maximum depth of the scour hole.