minasadat seyedjavad

 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.  

All tests have been conducted in a closed-loop rectangular Plexiglas flume in Soil Conservation and Watershed Management Research Institute (SCWMRI), Tehran, Iran. The study canal  was10m long, 0.6m wide and 0.6m high. All tests have been carried out on the 0.6m wide canal. To prevent flow turbulence upstream of the canal, tranquilizing racks were used at the upstream. A calibrated triangular weir was also applied to measure the flow at upstream. Also, a calibrated rectangular sharp-crested weir was used downstream. The water surface profiles were measured longitudinally. For this purpose, a digital depth profiler with 0.1 mm precision was used. The profiler accuracy was valid for almost stable water surface but it could be decreased in highly turbulent flows. An electromagnetic velocity meter with 0.001 m/s precision was used to determine velocity components to obtain parallel (𝑉𝑥) and perpendicular (𝑉𝑌)to the side weir. The profiler and the velocity meter could move on a rail in both X and Y directions. Flow rates at the main and the collection canal were measured by a calibrated 90° V-notched and a rectangular weir, respectively. Figure 6 shows a general view of the laboratory. In this research, 16 models of Type-A trapezoidal weirs have been studied in two cases of 1 and 2. The weirs had 3mm thickness made of Plexiglas. The tests were carried out preventing the effects of viscosity and surface tension over the weir and considering the height of more than 3 cm.  

In this research, for investigating the effects of a number of inlet cycles, the weirs were tested at two different directions of the side weirs located in the main canal. The results showed that the weirs with 15cm and 20cm had the highest discharge coefficient CM in dimensionless ratios of 0.2> H/P> 0.4 and H/P>0.5 respectively. Having reviewed previous studies, it could be concluded that the trapezoidal piano key side weir was capable of releasing a flow 1.2 times more than that of the linear trapezoidal labyrinth weir with 12 degrees angle and 1.87 times more than the one with 6 degrees angle, and 1.5 times more than that of the triangular labyrinth weir. 

The results of the present study showed that these types of weirs could have a better lateral performance than other weirs. In addition to this research, other researchers can conduct detailed studies on sedimentation and sediment control in this type of weir.   Keywords:Discharge, Flow, Water Diversion Structure

The main application of spillway in rivers and dams reservoirs is control and diversion of flood and protection of their related structures. In this research, a laboratory study was performed to test 16 trapezoid piano key A type weir models with different pillars 10, 15 and 20 cm in a canal with 10 meters length, 0.6 m width and 0.6 m height. The proposed weirs were placed on the main canal wall with two arrangements. The results showed that the maximum overflow rate coefficient was corresponded to weirs with p=15cm in both arranments (1 and 2) and the dimentionless ratio of 0.4 <H/P> 0.2 0.4 and also to weir with dimentionless ratio of 0.5 <H/P and p=20cm. Finally, the trapezoid piano key weir with a p=15cm and a B=50cm identified to pass the most appropriate flow regime.

Spillway is a hydraulic structure that is used to cross overwaters and floods from upstream to downstream of dams. Side weirs are a variety of hydraulic structures that are designed for various purposes in water transfer systems. The side weirs is constructed with an elevation less than the wall height of the canal, and when the water level rises, spillway will regulate the flow rate and control the water level in the main channel. This research done, in a laboratory review, a canal with a length of 10 meters 0.6m wide, 0.6 height and 16 types of piston cluster type A trapezoidal piano key side weir with different tripods 10, 15 and 20 cm. The above-mentioned overflows are under consideration. The results show that the overflow with a base of 15 cm in both cases has a maximum flow rate coefficient in the ratio of the0.2> H/P> 0.4and has a fluctuation ratio of 0.5

Measuring sensitivity of hydraulic structures is considered as an approach for evaluation of water projects performance, due to lower distribution efficiency in Irrigation and Drainage project schemes. Sensitivity analysis approach for irrigation structures is one of flow analysis methods which are developed in recent years in order to measure the behavior of flow in hydraulic structures in an irrigation network. This study examines the sensitivity of offtake structures in Varamin irrigation and drainage network project, which is one of the modern networks in Iran. The sensitivity measurement was carried out by the use of collected data from field in years of 2010, 2011 and 2012, and compared them with the water requirement for crop pattern calculated by CROPWAT model. Flow channel simulation was conducted in the project to identify the most sensitive offtake structures, due to inappropriate allocation of water particularly in downstream of network. Simulation and evaluation were carried out using SOBEK hydrodynamic model, and relationships introduced for sensitivity measures for offtake structures. Investigations and sensitive analysis on hydraulics structures in Varamin Irrigation network showed that Baffle modules have significant sensitivity. According to reviewed equations, sensitivity of Baffle modules is related to upstream depth, and opening of NEYRPIC module gates; which occurred more in terminal structures. The best way to have an optimal operation in this network is supply of required water depth in downstream of each canal. In these circumstances, the water depth in all offtakes is provided, and does not make any changes in the opening modules also.

Increasing the flexibility of water distribution and delivery and reducing water loss by downstream control systems plays a crucial role in improving the network performance. With respect to this issue، the use of performance indicators for evaluating irrigation systems is indispensible. In this paper، the original design of Varamin irrigation network was evaluated and compared with the 7-day irrigation period and off night operation with specific conditions. Furthermore، the effect of off night operation in the sensitivity of control structures (duck bill) in downstream of the network was evaluated. The result revealed that off night operation had a better performance compared to the 7- day irrigation period. Thus، there is more water available for downstream farmers in the off night scenario rather than 7- day irrigation period scenario. Besides، they can gain as much water as upstream farmers gain.

According to the low efficiency of irrigation and drainage networks and water distribution in Iran، simulating water flow and sensitivity structures and networks is considered as a new approach to evaluate the performance hydroelectric projects in the country. In this study، because of reduced water supply and distribution، especially in downstream irrigation and drainage networks Varamin to evaluate the sensitivity network in off takes structures. The sensitivity of the survey data by examining Water original data and compared them with the amount of water needed to grow the network. Network simulation and analysis using hydrodynamic model Sobek presented for sensitivity and relationships off take structures is done. Studies and sensitivity analysis for hydraulic structures Varamin irrigation system showed that baffle modules sensitivity are considerable. The study of equations، the sensitivity baffle modules occurred more than the depth upstream and valve patency rate in terminal structures. For optimal operation of the irrigation system in Varamin best way to provide for downstream water depth of each channel. In these conditions، the water supply and wastewater in all modules in the patency rate does not change.

Increasing the flexibility of water distribution and delivery and reducing water loss by downstream control systems plays a crucial role in improving the network performance. With respect to this issue, the use of performance indicators for evaluating irrigation systems is indispensible. In this paper, the original design of Varamin irrigation network was evaluated and compared with the 7-day irrigation period and off night operation with specific conditions. Furthermore, the effect of off night operation in the sensitivity of control structures (duck bill) in downstream of the network was evaluated. The result revealed that off night operation had a better performance compared to the 7- day irrigation period. Thus, there is more water available for downstream farmers in the off night scenario rather than 7- day irrigation period scenario. Besides, they can gain as much water as upstream farmers gain.