الفهرس 
INTRODUCTION AND LITERATURE REVIEWOnly 14 pages are availabe for public view
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Abstract
Recent developments of air valves incorporate an additional function, appropriating the valves to reduce pressure surges and alleviate the pressure spikes associated with the (dynamic closure) ”blow-shut” of the large orifice of the air valve. The behavior of one of these valves, Vent-O-Mat 3-stage air valve (RBX 25), and its behavior as a 2-stage air valve, the initial filling of a pipeline from an upstream tank maintained at different upstream pressures were investigated both experimentally and numerically. Throughout this work, more understanding of the dynamic behavior of air valves during transient is achieved. A wide range of tests were conducted, the aim of which were to obtain a graphical representation of the differential pressure versus water discharge rate characteristics for different valve float configurations and to determine the exact point at which dynamic closure occurs, whenever it occurs, and to determine the peak pressure induced when a flow of water column reaches and closes the valve. The test rig for water discharge tests was constructed from a transparent pipe, and also transparent valve was used to allow visual interpretation of the valve behavior during transients using high speed camera. The rig was interfaced with a high pressure air/water supply in order to obtain the necessary pressure difference to vary the water column velocity. Pressure record was monitored and recorded at different locations along the pipe and at the valve. Water column velocity was also recorded via an ultrasonic clamp on flow meter. The outputs of the various sensors were monitored by means of a data acquisition device. from the experimental results the switching criteria could be defined, monitored and measured. On the other hand the experimental results have been compared with the results of the numerical model that has been developed based on the method of characteristics with its ability to simulate complex pipe systems, unsteady friction, viscoelastic pipes and column separation. The air vent was incorporated in the model as a boundary condition.