نشریه سد و نیروگاه برق آبی ایران
پیاپی 11 (زمستان 1395)

By increasing in construction of large dams, the needs for increasing the safety of flood discharge structures are necessary in design. Overflow spillway and sky jump as a terminal structure downstream of spillway are frequently used in dams. In the present study, the spillway and sky jump of Glevard dam are modeled by Flow-3D software and their hydraulic parameters are studied. Verification tests revealed that RNG turbulence model is the most convenient turbulence model. Sensitive analysis showed that the more suitable mesh size is 0.6 meter. Analysis of hydraulic characteristics of flow showed that the occurrence of cavitation at the end of chute is more probable. In the sky jump, the occurrence of positive pressure prevents of cavitation. The changes in geometry of bucket such as the angle of lip and the radius of bucket are investigated. Increasing the angle of lip about 20 degrees, increases the length of jet until 40 meters.

This paper includes modeling and simulation of 180 MW units of pumped storage power plant with Variable speed machines. In this method, voltage source inverters are used instead of traditional cyclo-converters. This paper aims to control the voltage source inverters and maintain DC voltage at a constant value. AC/ DC/ AC converter is used in system configuration structure in order to control and change voltage and frequency. AC / DC converter is a three-phase rectifier bridge as well as DC / AC converter is a single phase inverter which includes 12 IGBT (insulated gate bipolar transistor) and output includes constant voltage designed from inverters output. Firstly, the control structure of the machine and the transformer sections will be described and the block diagram of each part is shown, then the equations for each part descried and the overall control structure of plant will be achieved. The simulation of this methods by applying Matlab software have been presented.

In this research the effects of installed blades on the combined model of ogee spillway with lower bypass on energy loss of structure and downstream hydraulic jump characteristics has been experimentally investigated. In order to achieve the goal of this study, a physical model of ogee spillway with lower bypass was built, in which the output jet from the lower bypass (bottom outlet) was set to be at the angle of 30 degrees to the overflow of spillway. Installation of blades at the upstream of the lower bypass slit makes flow separation and more turbulence on spillway and as a result more energy dissipation on structure. In this research, two blades relative thickness including tb/ y1d= 0.07 and 0.14 were used and the results showed that the blades with the higher relative thickness (i.e. tb/ y1d=0.14) was found to be more effective in energy dissipation on structure and less values for the downstream hydraulic jump parameters. The measured values showed that the average energy loss on spillway, and the reduction length and secondary relative depth of hydraulic jump were 47.6%, 40% and 23.2%, respectively. According to the results obtained in this research study, the use of this structure is recommended for economical stilling basin construction at the downstream of small dams and spillways.

Flood routing calculations are divided into hydraulic and hydrologic methods. Hydraulic methods are based on solving Saint-Venant equations and they enjoy high accuracy. Although hydrologic methods are in low accuracy, they are taken into consideration by researchers because they are applied so easily. In this research, multilinear Muskingum’s parameters were derived according to the mentioned cross sections. Then by comparing routed hydrographs with multilinear Muskingum method and Saint-Venant model, reference discharge coefficients were optimized and their values became one in horseshoe cross section. Afterward, based on these coefficients different hydrographs were routed was obtained by using continuity equation. The percentage error in simulating peak of the discharge hydrograph in horseshoe cross sections was calculated %0.7 and the time to peak discharge was estimated the same in both models and cross sections.

Dam reservoirs are cosnidered as impronatnt hydraulic structures in water resources management and flood control. Therefore, reservoir operation and method of water release has sepcial importance. In this study, a new alorithm is used for reservoirs operation. This alorithm is a combination of Harmony Algorithm and Particle Swarm Optimization (PSO) algorithm, and supports these two algorithms such that it solves the problem of lack of balance between exploration and exploitation. This hybrid method improves the harmony method so that the trap probability in local optimum is decreased. Moreover, the hramony method hepls to correct the responses which don’t fall in feasible space of the solution in PSO method. The hybrid method was used for Mahabad and Karun 4 dam reservoirs, aiming at reducing the shortages and/or enhancing hydropower generation. Results showed that the hybird method has closer resposes to global optimum, as compared to the other two methods. In additon, simulated results of water release, storage, and genrated power in Mahabad and Karun 4 reservoirs match very well to nonlinear-programing results obtained by using Lingo software.