Flow dynamics in a pipe containing uneven roughness elements

[EN] The objective of this study is to improve the methodology for modelling aged pressurised urban networks, such as water distribution system (WDS) pipelines, with substantial and uneven wall roughness. Due to the complexity of the inner surface geometry of old rough pipes, WDS models are unable to predict the real velocities, which are requisite for estimating contamination propagation rates in the system. In order to analyse the impact of inner surface geometry a specifically designed experimental apparatus was built to investigate the flow dynamics in a pipe containing flow-obstructing elements. A transparent pipe was fitted with 3D-printed elements, in two different configurations, at the location of the measurement section and the velocity fields were captured using the particle image velocimetry technique at different flowrates. The experimental results revealed that in the case of one roughness element, the impact to the flow dynamics is local and can be expressed through minor losses, and in the case of multiple elements, the effective diameter of the pipe is reduced and a jet-type flow will develop.