Rafigh, S; (2013) Transient hydraulic flow modelling for failure of pipelines transporting incompressible liquids. Doctoral thesis , UCL (University College London).

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Abstract

This thesis describes the development, fundamental extension and extensive testing (validation and verification) of mathematical models for predicting outflow following the failure of pressurised pipelines containing incompressible liquids. The models, for the first time, account for all the important sequential flow regimes taking place during the discharge process. These include full pipe flow, bubble formation and propagation, followed by open channel flow. The system configurations modelled include a draining pipeline connected to a storage tank and pipe with one closed-end. In the first part of this thesis, the development of outflow models to simulate the full-bore rupture of horizontal pipelines is presented. In order to model the full pipe flow in a pipe fed from an upstream tank, the published model by Joye & Barrett (2003) is employed in this study. Bubble propagation and open channel flow for both configurations (in the presence of upstream tank and pipe with one closed-end) are modelled by assuming critical flow condition throughout the pipe and in the tank (where applicable). Bubble propagation velocity is calculated based on Benjamin’s (1968) and Bendiksen’s (1984) proposed equations. The second part of this study focuses on the extension of the developed models to account for pipe inclination angle. Bubble propagation and open channel flow are modelled by replacing the critical flow equation with Darcy-Weisbach equation, applicable to downward-inclined pipes. The bubble propagation pattern in the pipe is determined based on the drift velocity method through the results obtained from parametric studies. The developed models are validated by comparing the predicted values against experimental measurements recorded using laboratory scale setups. Through sensitivity analysis based on comparing the results of the models to case studies representative of real events, the importance of accounting for post-full pipe flow on the total amount of inventory discharged is demonstrated.

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