عنوان مقاله [English]
نویسندگان [English]چکیده [English]
The most common underlying cause of unsteady flow, opening and closing the valve fusing of current. This action will cause pressure waves in the system. Pressure wave speed depends on the type of valve, the valve opening and closing speed, hydraulics system and property of elastic pipes. One of places where it is important to calculate hammer, water conveyance systems are hydro power plants. If for any reason during the operation of the hydro power station turbines out of the circuit, the water hammer will be caused. This phenomenon not only pipelines, but also damage the turbine and power plant installation. Therefore, issue of water hammer in the transmission system is a concern for many researchers' hydro power plants. In this study to determine the effect of unsteady shear stress in fast and slow closing of the wicket gate valve used computer code. In order to calculate the shear stress from two equations Daily et al and the equation of friction developed Brunone et al a computer code was used. The results obtaines that the pressure wave in a fixed the Reynolds number in the first cycle was almost identical in both methods of friction and in the next cycle, pressure waves generated by the second method (equation developed Brunone et al) damping is greater than the time. In which case, both fast and slow closing of the wicket gate valve, the non-dimensional maximum damping the second method by 75%.