Irrigation and Drainage Structures Engineering Research
Year:2020 | Volume:20 | Issue:77|Papers Count:8

Introduction: Drip irrigation in which water is only available to the plant, is increasingly used in recent years. Since the flow behavior inside the emitter is difficult due to their complex structure and small size, in present study an attempt was made to assess the flow behavior of the emitters using mathematical and physical models. It needs to be mentioned that analysis of flow behavior of water in labyrinth channels is difficult because of micro-characteristics of the emitter. In this context Zhang et al. (2007) modeled the emitter’ s flow path using fluent software. In this investigation two physical models namely: laminar and turbulent were used to simulate the flow. Also numerical models that have been tested in experimental conditions, were used in the hydraulic analysis of Emitters. Next, Fluent software was used to simulate the behavior of the flow inside the two long-path emitters for calculating the discharge-pressure relationship of the models and results were compared with results obtained from experimental results...

Introduction: A side sluice gate is an underflow and metering diversion device set into the side of a channel with the purpose of allowing part of the liquid to spill through the side. Review of the literature shows that in spite of the importance of the side sluice gate, little attention has been given to studying the behaviour of flow through this device. The available published works on side sluice gates found are those of Panda (1981), Swamee et al. (1993) and Ghodsian (2003). They related the discharge coefficient of the side sluice gate to depth of flow and gate opening. For this purpose, the side sluice gates, since flow control devices, are widely used in the irrigation channels to divert flow from a main channel to a secondary channel. The main purpose of present study was to determine the water surface profile, gate opening, and flow discharge through the sharp-crested rectangular side sluice gates in a subcritical flow regime in free and submerged flow conditions. This study also provides some approaches to differentiate the free or submerged flow conditions. For this purpose, two approaches of solving spatially varied flow equation in a sub-critical flow regime and the direct solution of the discharge equation of the side sluice gates in determining the flow characteristics of the side sluice gates was experimentally investigated...

Introduction: The cost of dam construction is very high. A lot of dams are broken due to the water passing through dam crest. The most important factor which causes this is, insufficient spillway capacity. The aim of present study was investigating optimal height and length for Ogee-Crested spillway because such height and length minimizes the cost of spillway construction. In order to determine objective function, the spillway length variations were considered in the range of 10 to 30 m and the flood return period was estimated in the range of 1000 to 10, 000 years. Optimization was done with using genetic algorithm in MATLAB software environment. In fact, the aim of this study was investigating the effect of height and length of spillway on the cost of spillway construction, therefore, Analytical relationships presented with using regression model. The main function of Ogee-Crested spillway is providing ideal conditions for passing designed flood from upstream to downstream. Bagatur & Onen in 2016, used gene expression planning (GEP) models as an alternative approach to predicting appearance features and spillway design coefficients and therefore, proposed new relationship, for Ogee-Crested spillway. It was found that GEP is much better than regression model for predicting Ogee-Crested spillway characteristics. Haghbin in 2015 proposed that using multi-objective genetic algorithm can optimize spillway geometrical dimensions...

Introduction: Piano key weir (PKW) is a hydraulic structure that can be installed at dams and canals for regulating the flow surface and discharge. The main feature of this weir is the ability to pass a large flow of water over a small head. Regarding its geometrical properties, this weir is classified into four types of A, B, C and D. PKW with symmetrical upstream and downstream overhangs is classified as Type A, one with only upstream overhangs as Type B, one with only downstream overhangs as Type C, and one without overhangs as Type D. Despite various studies on piano key weirs (some of which were mentioned in the text), the flow behaiviour over these structures is very complex, unpredictable and three-dimensional. So further laboratory investigations on PKWs are needed. In the present study, the effect of the width of the inlet and outlet keys on the hydraulic characteristics of these weirs is investigated. In addition, the occurrence of undular flow on these types of weirs is reported for the first time. To achieve the aims of this study, more than 300 experiments were conducted at a laboratory flume...

Introduction: Water distribution uniformity is a key in pressurized irrigation systems. Pressure fluctuations due to topographical changes, local and frictional head losses, and different water uses are considered of great concerns. Any mechanical device with the ability to keep an almost constant flow delivery, irrespective of the pressure fluctuations is of great practical importance. In this regard, a flow control valve is a useful tool. A flow control valve is a mechanical choked orifice plate structure including a float-spring mechanism inserted in an ordinary orifice (Zhang and Wang 2015). Such a valve is not yet produced commercially. In this study, the effect of the spring elasticity mainly due to spring fatigue is investigated experimentally on the valve performance. Also, the changes in the installation location of the float, when the valve is in rest condition, may affect its performance. To quantify this effect a detailed experimental plan was performed...

Introduction: Formation of air-entraining vortices in an intake leads to unsteady flow and cause problems such as vibration in hydro mechanical equipment, abnormal noises, severe fluctuations in local pressures and exacerbated cavitation conditions (Chen & Chen, 2015). As stated by (Sarkardeh, 2017) the stronger vortex the greater will be its negative effects on intake performance. There have been many studies on the critical submerged depth and vortex formation in intakes. (Kocabas & Yildirim, 2002) investigated the effect of rotational flow on the critical submerged depth in intakes and found that the vortex formation with the air-core vortex and the critical submerged depth was significantly dependent on the approach flow conditions and the inlet geometry. Therefore, a separate case study should be undertaken to address any structure with a particular geometry. In this paper, the effect of flow rate deviation due to the use of a deflector on a vertical intake was investigated. In this paper, also the variation of submerged depth, Froude number, vortex type, and critical submerged depth was discussed...

Introduction: Conveyance and Water distribution irrigation canals are hydraulic structures that transport water supplied from sources such as diversion dams for drinking, agricultural, industry or other purposes. These canals are usually lined by materials such as: concrete, stone with sand cement mortar, asphalt, to prevent water seepage losses along the flow path. Concrete lining that is used in irrigation canals is an unreinforced concrete with a thickness of 5 to 10 cm. Basic requirements of good hardened concrete are: satisfactory compressive strength and sufficient durability (Aba, 2005). After the implementation of each engineering structure, it is necessary to evaluate the project to determine the optimal performance and quality of implementation. Evaluation of the quality of irrigation canal linings is often carried out by the destructive and costly method of coring and carried out various experiments in the laboratory. Although destructive method yields relatively exact and straightforward results from the desired parameters, it also has some side problems that are sometimes difficult to recover. The problems of destructive test (DT) method with coring and destructive method are associated with damage of project, high cost, need the expert group and equipment, time-consuming and sometimes stoppage of project operation. Non-destructive testing (NDT) methods can be used to prevent these complications. Electrical, ultrasonic and Schmidt hammer tests are among non-destructive testing...

Introduction: The stability of unsaturated slopes during rainfall is an important natural hazard. Past studies have shown that slope failures generally occur during or after rainfall. A review of past studies shows that instability of natural or excavated slopes for infrastructure construction occurs mainly during or after rainfall. Due to rainfall infiltration into unsaturated soil, the apparent cohesion and shear strength provided by matrix suction reduces d, resulting in slope instability. Library studies for this research, revealed that in recent years, extensive studies have been conducted on the rainfall infiltration in unsaturated slopes and their effect on shear strength and stability. But much of the research has been on high-intensity rainfall over a short period of time, however, some instability of slopes occurs during long-term rainfall or after rainfall. In addition to field research and physical modeling, numerical methods have also been developed to solve complex problems of unsaturated soils within the framework of various scientific theories in recent years. In this paper, in addition to considering the results of previous studies, the stability of the excavated soils with multiple berms has been investigated by considering transient fluid-mechanical coupled analysis...