126 publications from this institution
Water utilities are concerned about the issue of pipeline collapses, as service interruptions lead to water shortages. Pipeline collapses can occur during the maintenance phase when water columns compress entrapped air pockets, consequently increasing the pressure head. Analysing entrapped air pockets is complex due to the necessity of numerically solving a system of differential equations. Currently, water utilities need more tools to perform this analysis effectively. This research provides a numerical solution to the problem of entrapped air pockets in pipelines which can be utilised to predict filling operations. The study develops an analytical solution to examine the filling process. A practical application is shown, considering a 600 m long pipeline with an internal diameter of 400 mm. Compared with existing mathematical models, the results of the new analytical equations demonstrate their effectiveness as a new tool for computing the main hydraulic and thermodynamic variables involved in this issue.
The number of cycles of earthquakes is an important factor in simplified assessment methods of the liquefaction potential of soil. Herein, a set of correlations was obtained for several definitions of the number of cycles by peak counting (NP) and duration of large-magnitude earthquakes to verify whether the duration can be used as an indirect measure of the number of cycles for assessing the soil liquefaction potential. Additionally, a novel criterion for bracketed significant duration (DBS) estimation was suggested based on intervals of cumulative absolute displacement (CAD). The most strongly positive correlations between the number of cycles and duration definitions were obtained for NP and bracketed duration (DB) based on absolute thresholds rather than relative thresholds, suggesting that absolute thresholds are more appropriate for liquefaction potential assessment. While duration is an important factor for understanding the behaviour of the number of cycles of large-magnitude earthquakes, it does not provide a comprehensive explanation. To reduce the dispersion in the correlations, additional parameters, such as frequency content, should be incorporated in the analysis.
The prediction of the pressure inside the air pocket in water pipelines has been the topic for a lot of research works. Several aspects in this field have been discussed, such as the filling and the emptying procedures. The emptying process can affect the safety and the efficiency of water systems. Current research presents an analysis of the emptying process using experimental and computational results. The phenomenon is simulated using the two-dimensional computational fluid dynamics (2D CFD) and the one-dimensional mathematical (1D) models. A backflow air analysis is also provided based on CFD simulations. The developed models show good ability in the prediction of the sub-atmospheric pressure and the flow velocity in the system. In most of the cases, the 1D and 2D CFD models show similar performance in the prediction of the pressure and the velocity results. The backflow air development can be accurately explained using the CFD model.
