Author(s): J. Gale; A. Bergan
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Keywords: No Keywords
Abstract: The (beneficial) dynamic response of the air valve during the fluid transient is twofold: (i) to suppress sub-atmospheric pressures by admitting air rapidly with the aim to avoid cavitation and column separation (after transient events, flow interruptions, draining and system shutdown), and (ii) to control the extreme pressures by releasing air slowly with aim to avoid high peak pressures (during filling, system start-up). In this manner a comprehensive experimental programme for investigating dynamic behaviour of air valves in large diameter pipelines had been undertaken at WL|Delft Hydraulics, the Netherlands, by a consortium of researches from 5 institutions with the support of MRI Programme of EC. The experimental work at WL|Delft Hydraulics consisted of (i) steady flow tests with air, (ii) dynamic tests with air admission, (iii) dynamic tests with air release and (iv) dynamic tests with air admission and air release. Larger amount of high quality experimental data was applied for validation of our physical model of water hammer transient with special model for description of dynamic response of the air valve. The set of first order partial differential equations is being solved with second order characteristic upwind finite difference numerical method, which is based on Godunov’s methods. This paper describes, discusses and validates the applied physical model, numerical method and results of our research work on numerical modelling of dynamic response of air valves during transients. Preliminary results exhibit reasonable agreement of prediction and measurement and it is shown that appropriate design of air valves prevents and/or mitigates cavitation effects during transient occurrences in piping systems.
Year: 2010