Irrigation and Drainage Structures Engineering Research
Year:2020 | Volume:21 | Issue:78|Papers Count:8

Introduction: One of the important parameters of water quality is the high level of dissolved oxygen (DO) content that is essential for the survival of all aquatic organisms and water quality improvement. Aeration refers to the physical process of oxygen absorption from the atmosphere and enhancement of the dissolved oxygen of water. Some hydraulic structures enhance the oxygen transfer by creating a great deal of turbulence and entering air bubbles. Stepped spillways are efficient in terms of air bubble entrainment. Advantages of stepped spillways include strong turbulent mixing, a large residence time and a substantial air bubble entrainment. Moreover, based on the laboratory data, some researchers have studied the aeration performance of labyrinth weirs in order to develop regression models for the prediction of aeration efficiency. The experimental results showed that the labyrinth weirs aerated significantly better than the normal weirs, especially at the lower drop heights. One of the methods to increase the content of dissolved oxygen is installation of structures that help increasing turbulence and entering small bubbles of air into water body. A falling jet of weirs is a specific case of creating turbulence in the water and increasing DO...

Introduction: The flow passing through a side weir, one of the varieties of water diversion structures, is a variable flow with decreasing flow rate. Labyrinth weir is the basis for piano key weirs. They are often constructed with vertical walls and are much more efficient than the linear weirs. Nevertheless, the flow, especially the bottom flow, enters this type of weirs and passes through two vertical walls of the side crests. Then it becomes squeezed and therefore the upstream and downstream crests come up with inappropriate hydraulic behavior. Also, the most outstanding disadvantage of this type of weirs is the large foundation area needed to be constructed on the concrete dams. The piano key weirs are a modern type of the nonlinear weirs which have been developed by Hydro Coop Institute of France and the Hydraulic and Environmental laboratory of the Biskara University of Algeria. In general, these weirs comprise of 4 different types, the differences of which lie in the presence or the absence of slopes created for them. Type A is sloped both upstream and downstream, Type B is sloped upstream, Type C is sloped downstream and Type D lacks any slope. The present study conducted show the effective geometrical parameters on the hydraulic performance and discharge coefficient (CM) of the trapezoidal piano key side weirs (TPKSW). The type of flow and its variations in a side weir can be considered as the C_M of the side weir, using simplifications and assumptions suggested by De-Marchi in 1934 to obtain suitable equivalents for side weirs...

Introduction: Dam reservoir sedimentation is known as one of the main serious problems that mainly affects the efficiency of dam's operation. Sedimentation may also block the conduits and it can destroy turbines, sluices, and valves. So it is necessary to find a way to solve this problem. In this regard, hydrosuction considered as a proper alternative and a potentially efficient method to remove the superficial deposited sediments from reservoirs. Hydrosuction system consists of a large pipeline working with an inlet suction tube lying on deposited sediments in the reservoir. In hydrosuction systems, the deposited sediments are withdrawn, as a mixture of sediments and water, from the reservoir and directed to downstream. The major advantage of using hydrosuction method is its economic aspects since the system doesn’ t need extra energy for operation. Environment friendly method, hydrosuction can be used all over the reservoir, where the output and the volume of sediment removal could be under control. Researchers have tried to evaluate and improve the efficiency of this system. In this study, the effects of different shapes and forms of the suction mouth (tube inlet) on the efficiency of hydrosuction system in sediment removal were investigated. To achieve this goal, several experiments were carried out using different shapes of the suction mouth including the plain-type (circular) and wedge-shaped in the middle of the suction mouth...

Introduction: In recent years, the advancement of computer science helped to examine digital elevation models (DEMs) that are produced in various methods. It is possible to study DEM at different scales. These scales are: 1-fine grain scale, 2-meso scale 3-reach scale, and 4-catchment scale. Determining and studying the digital elevation model of the bed in each of these scales is important. Today, the advances achieved in computer science and its combination with engineering sciences, including river engineering, have led to new approaches in this field. One of the most widely used devices is the Kinect. The use of the Kinect for scientific purposes was first introduced in 2013 by David Monkoff as a cheap, high-precision instrument to produce three-dimensional models that could be used in a wide range of scientific studies such as geology, geomorphology and bathymetry (Mankoff & Russo, 2012). In this study, the ability of Kinect device to determine the DEM of sand bed in the Kordan River, as a method for determining the roughness of natural riverbed, has been investigated by comparing the average and relative error of DEMs prepared by Kinect and theoretical models...

Introduction: Using hydrological information and physical and hydraulic characteristics of the river route for flood routing in different cross sections of the river, impact of forecasting on the occurrence and flow peak flow and successful implementation of flood alarm systems and forecasting flood volume downstream of the river. Given the importance of predicting flood hydrographs, especially in flood plain rivers, and the lack of sufficient information and statistics at some river basins, this may result in hydraulic methods in such rivers. This study aimed to compare the results of flood routing using the numerical model MIKE11 and the support vector machine method. This comparison was based on three parts: peak discharge, flood volume and baseline hydrograph time...

Introduction: Local scour around piers and bridge abutments is one of the reasons for instability and destruction of the bridges. Local scour of a bridge foundation is almost inevitable as far as rivers are concerned. There are generally three types of scours that affect the performance and safety of bridges: local scour, contraction scour, and degradational scour. During the last decades, different arrangements were proposed to protect bridges against local scour. The arrangements for local scour at bridge piers can be grouped in two categories: armoring devices and flow-altering devices. Flow altering devices that have been used to protect piers against local scour include protecting piles placed upstream of the pier, Iowa vanes, and flow deflectors attached to the pier, such as collars. This study addresses the effectiveness of collars on scouring reduction around abutments and pier bridges. Despite the availability of various studies about the effects of collar on scour at bridge pier and abutment (such as Laursen & Toch, 1956; Mashahir & Zarrati, 2002; Kayaturk, 2005 and Khozeymehnezhad et al., 2014), and due to importance of bridges structures, further laboratory investigations are needed to explain the different aspects of collars interactions with abutment and piers scouring phenomena. So the purpose of this study was to study the effects of different sizes of collars on a rectangular abutment and their location to the surface of the sedimentary abutment on bridge group piers scour reduction at the presence of debris...

Introduction: In reservoir dams, high kinetic energy at downstream of their spillways can cause destruction of the spillway and its surrounding areas which results significant loss of life and financial loss, so it is necessary to investigate the performance of energy dissipation structures during its operation. In this regard, the effects of the number of deflectors located just donsream of its chute on energy dissipation and its projectile length were investigated experimentally. Deflectors separate the incoming jet to few smaller jets, which pass through the slut between the deflectors or overflow above the deflectors. Therefore, more air mix with the jet flow and the separated jets hit each other, the results of which are increase in the amount of energy dissipation. On the other hand, the existence of deflectors reduces projectile length, makes smaller submerged ponds easier to maintain, and reduces costs...

Introduction: In Khuzestan province, waste water release from various sources, especially from agricultural farms, is a serious problem. The volume of drainage water resulting from irrigation and drainage networks of the Karun river basin is about two billion cubic meters per year, considering sugarcane agro-industries and fish farming as the main sources of drainage water. Time-Averaged salinity of this drainage water, with source of sugarcane agro-industries, is about 6 dS/m which is valuable to irrigate salt-tolerant crops or aquaculture with saline water as part of the solutions for drainage water management and providing sustainable environment. This can also affect the amount of water allocated to irrigation networks and sugar cane industries. In this regard, reusing of agricultural drainage water to produce rice salinity resistant varieties and lines as a high-yielding strategy in Khuzestan, especially in the central and southern areas with high water demand, can be very useful...