Study of Effect of Distance and Diameter of Leak on Hydraulic Properties of Unsteady Pressure Waves

Having unsteady flow in water supply systems due to the change from one stable state to another stable state is inevitable. On the other hand, over time, the various causes lead to the pipeline leakage or even a pipe fracture. So, with presence of leak, investigation of characteristics of unsteady flow that is an integral part of the hydraulic system will be of particular important. In current study, the fast unsteady flow that is one of the most damaging types of flow is simulated by laboratory considering leak in pipeline and with respect to that, the impact of leakage characteristics such as size and location of the leak on the hydraulic properties of unsteady flow will be evaluated. The experiments were carried on a tank, pipes and valve system that made of 63 mm polyethylene pipe with length of 47 meters and a height of 5 m for static water head in tank. A total of 3 discharges, 4 leakage diameters, 4 leakage positions and 2 fasten time of valve were tested that illustrate gradual valve fastening cannot show the leakage in pipeline system. Peak pressure drop in the first period of wave increases with increasing diameter and slope of the pressure drop caused by a leak in the first peak are faster for the leaks that nearer to the valve. Also, the pressure wave damping slope is steeper in the case of leakage with a greater diameter than leakage with a smaller diameter.