نشریه سد و نیروگاه برق آبی ایران
پیاپی 23 (زمستان 1398)

There is a pressure tunnel as the type of structures, which is mainly used in the hydroelectric power industry and in order to design and construct these structures, there are many engineering challenges. One of these problems is the leakage around the tunnel and, consequently, erosion caused by excessive water pressure, and it will lead to instability and the destruction of pressure tunnels. The main objective of this paper is to investigate and evaluate the numerical effect of internal pressure and the water leakage force simultaneously in the design of pressure tunnels. To accomplish this, water tunnels have been modeled and analyzed with different levels of groundwater and different overheads, under the influence of internal pressure using PLAXIS3D software and the finite elements method. The results indicate that due to the internal water pressure and the leakage force, by increasing the water level to tunnel overhead, the overall deformation of the tunnel has decreased and the incidence of stress has increased. Also, increasing the ratio of the depth of overhead to the diameter of the tunnel increases the amount of general and shear bends, and the axial and shear forces and the bending momentum on the tunnel cover decreases.

Projects include activities that must be carried out at certain dates, with specified costs and determined qualities in order to satisfy the stakeholders. Project control is one of the most important and widely used issues in project-based organizations and it has attracted a lot of attention. So far, in the field of project control, there have been a lot of research that were done in different ways, which illustrates the application and importance of this issue. A significant point in all projects is the prediction of project time and costs. This will give project managers an opportunity to accurately evaluate the time and cost of completion of projects, and to minimize the delay in project completion and the budget deficits through more detailed project planning. This research aims to predict the project time and cost using the trapezoidal fuzzy number based on earned value management. This method can be used in the situations in which the conditions are uncertain and the percentage of real progress and program work are expressed in linguistics and qualitative manner. Finally, in this paper, the presented method has been applied in a real numerical example.

Piano Key Weirs, a developed scheme of labyrinth weirs. In this study, 36 trapezoidal Piano Key Weirs models were conducted in 360 different geometric and hydraulic conditions. Experiments were conducted in a 11 m long flume with a rectangular cross section of 49 cm width and 70 cm height in which the effect of dimensionless ratios on the discharge coefficient was investigated. The results showed that L/W=6.54, B/P=2.33 and Wi/Wo=1.33 compared with other values ​​that have been tested in this study, increasing the discharge coefficient 113, 63 and 33 percent respectively, Therefore, they are suggested as optimal ratio for trapezoidal plan. Which is close to the ratio that other researchers have proposed for the rectangular plan. Also, by using SPSS software and taking correlation coefficient (R2) and Normalized Root Mean Square Error (NRMSE), relations was proposed to estimate the discharge coefficient and the sensitivity of the proposed relationship to its parameters showed that this relation shows the highest and lowest sensitivity to the L/W and Wi/Wo parameters respectively.

The rapid movement of sediments, which is often induced by a very erosive and transient flow in rivers and rivers, causes a lot of geomorphology and engineering problems. Failure of the dam with a moving bed, submerged landslide, sedimentation flushing in reservoirs are just a few examples of these problems. The study of waves is challenging due to the interference of several complex physical phenomena, such as the interaction of slide-water, turbulence and complex free-surface profiles. In recent years, the increased impact of earthquake hazards on human life around the world has increased the need to find economically acceptable methods for predicting the occurrence and degradation of landslide. Considering the importance of the subject, the purpose of this research is to provide and develop an appropriate mathematical model for simulating the landslide phenomenon by Lagrangian method. Due to the ability of the Lagrange method (MPS), this method is developed to simulate the phenomenon of landslide, and the system is considered as a multidensity and multiviscosity. The results of this numerical modeling have been compared with experimental results. The results indicate the accuracy of the proposed numerical method in modeling the landslide in a rigid and deformable state.

In this research, submitting a method for evaluation of detection cavitation specifications and also automation of cavitation threshold has been investigated. The case study was based on Kaplan hydro turbine data located on Tarik hydropower plant at Sefidroud dam. The foundation of method was employment MATLAB program, sensor classification sensor locations and cavitation sensitivity. For training in MATLAB program, 12 individual data sets and 4095 unique combinations were created and 408 data selected for examinations. The training data combined with sensor types and cavitation sensitivity features were employed to predict the cavitation threshold and the best training data set with more than 90 % accuracy. The results showed that the use of a fully automated process for sensitivity determination and cavitation classification was more suitable than the use of a process based on manually selected methods. The proposed research is useful for automation cavitation detection to hydro power turbine operators to predict the remaining useful life in futures.

Nowadays, with increasing problems related to lack of water resources and energy problems, the dam construction industry is dramatically expanding in our country. On the other hand, increase of threats to unify the vital systems of the country, causing financial losses through the use of various explosive devices, Has found a special need in the country. In this research, it has been attempted to simulate computers to investigate the mechanism of explosion charge loading on the dam body. Then, by analyzing the sensitivity to the amount of explosion load and applying changes such as increasing the thickness of the riprap, reducing the upstream slope and the downstream slope, reducing the normal water level and changing the dam characteristics, the effects of the explosion are compared with the original model. With the modeling of this dam in the finite element of ABAQUS and applying explosive loading on the upstream of the dam, it was observed that with increasing the thickness of the riprap, lowering the upstream and downstream slope, reducing the normal level of reservoir water and enhancement of materials, settelements decrease at the point below the explosion. Damage areas with a plastic strain of more than 10% are also reduced.

An important issue with respect to the hydraulic power systems is the frequency stabilization. To design Load Frequency Control (LFC) with high efficiency, control parameters need to be adjusted so that the system frequency remains stable even under changeable conditions. Controlling the frequency and changes in the turbine time constant requires that three term control parameters of Proportional-Integral-Derivation (PID) and Transient Droop Compensators (TDC) in hydraulic power systems be adjusted separately, without considering the damping parameters simultaneously with the load working condition. Owing to the significance of the above issues in hydraulic power systems, this paper aimed to study the adjustment of parameters using the methods of Particle Swarm Optimization (PSO), Desired Time Response Specification (DTRS), and Maximum Peak Resonance Specification (MPRS). The obtained results of simulation revealed that the method of Desired Time Response Specification (DTRS) is superior to the other methods under most conditions considering the frequency deviation and turbine output power.