نشریه سد و نیروگاه برق آبی ایران
پیاپی 15 (زمستان 1396)

Duckbill weirs have not a straight crest in the perpendicular direction to the flow. The plan view of the weir consists of multiple and broken linear crests that cause the increase of its effective length. The advantages of this type of weirs are higher discharge capacity, easy aeration as well as low fluctuations of water surface at the weir upstream. This paper deals with the simulation of the flow over duckbill weirs with triangle plan form to obtain its discharge coefficients. In order to simulate the flow over the weir, fluent software was used as a virtual laboratory. The turbulence and the free surface of the flow were modeled by k-ε RNG and volume of fluid (VOF) algorithms, respectively. The results were compared with the experimental results of Kumar et al. (2012) for curved plan crest duckbill weir. The comparison of the results indicated that the curved plan form weirs have the higher discharge coefficients (1.25 times the discharge coefficient of in triangular plan form for θ = 45◦) than the ones in triangular plan form. Also duckbill weir with triangular plan form in low hydraulic heads has good performance and the discharge coefficients are in a satisfactory range.

This paper presents modeling and simulating of a variable speed hydro power plant in which voltage source converters are used. Dynamic modeling of DFIM in hydro power plant is described using voltage source converters based on direct power control and differential equations are presented as models and their spatial representation is developed. In configuration of the system, a 3-level voltage source converter is used for controlling and changing voltage and frequency. Output includes a constant voltage, thus process of changing speed with faster dynamic response results in faster frequency response compared to other control methods .Investigation of two control methods shows that despite advantages of DTC, it has some problems including relatively high torque and flux ripple and variable switching frequency. These problems are due to improper selection of voltage vector and using hysteresis loop. For modeling and simulation the Matlab software have been used.

In this study, the performance of different turbulence models to simulate fluid flow through the turbine stator blades is studied. Navier-Stokes equations on computational grid discretized by using finite-volume method and the SIMPLE algorithm is used for coupling pressure and velocity equations. Two-equation models, k-e models (standard, RNG model, Realisable) and five-equation model (RSM) are applied to simulate the flow. foure region of the third stator blade are selected to compare current results to experimental results. present results show that k-omega turbulence model has a better model for simulation of such problems.

Flooding caused by dam failure is been one of the most awful events in the past two centuries. In this type of flooding, a considerable amount of water releases in the river downstream in a short time and causes huge waves in the coastal. Due to the nature of wave, the use of mathematical models is common for simulating advancing and spreading of flood caused by it. In this case study, the subsequences of the flood volume released by the failure of Mirza Shirazi storage dam that is under construction (in Fars province) and estimating of damage with respect to two probable dam break scenarios: 1) immediate failure due to overtopping; and 2) gradual failure due to overtopping, is been investigated. In immediate failure scenario, calculated peak of flood discharge at the point of failure was 118,000 m3/s and in gradual failure was 80,000 m3/s. The average velocity of water in the river bed in immediate failure scenario is 10.2 m/s and in gradual failure scenario is 5.06 m/s. The result estimated damage cost of flood caused by dam break, in scenario of gradual failure is 5578 billion Rials and in immediate scenario is 9136 billion Rials.

Using underground spaces with regards to population expansion and the troubles of rail transportation is one of the basic infrastructure in developing countries. To this aim, life preservation of people and servicing them in important instances like accidental explosion conditions has a special importance. the dual application of tunnels and underground metro stations both as a sanctuary and as a means of transport; therefore, investigating the explosion impact in such constructions and an appropriate estimation about the imposed loads on them through the explosion is one of the most important aspects of passive defense.
In this study, the effects of tunnel cross-section geometry on the performance of the tunnel under explosion loading have been investigated using centrifuge modelling. Cross section of tunnels modeled in this study consists of rectangular, horseshoe and circular. According to the results, optimized cross-sections can be circular or horseshoe design is based on design targets.

One of the major problems in successful implementation of projects that leads to the loss of many financial and human resources is the lack of good managers. Failure to pay attention to the competencies of managers during different stages of management of construction projects is one of the main factors of inefficiency of the project in achieving the goals predetermined. Therefore, it is important to identify the key competencies required by the project managers to succeed in the field of human resource management of the project. The results show that the impact of project management competencies on the HRM process is positive and relevant. The effect level for behavioral competencies has been higher than other competencies. Also, the behavioral competencies of project management have had a greater impact on the project team management process than other HRM processes, which shows that project managers can improve project management by increasing their behavioral competencies, and thus the HR management process The project is more successful.