Browsing by Author "Viseu M.T."

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Backflow air and pressure analysis in emptying a pipeline containing an entrapped air pocket
(Taylor and Francis Ltd., 2018) Besharat M.; Coronado Hernández, Óscar Enrique; Fuertes Miquel, Vicente S.; Viseu M.T.; Ramos H.M.
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. © 2018, © 2018 Informa UK Limited, trading as Taylor & Francis Group.
CFD and 1D simulation of transient flow effect on air vessel
(BHR Group Limited, 2018) Besharat M.; Coronado Hernández, Óscar Enrique; Fuertes Miquel, Vicente S.; Viseu M.T.; Ramos H.M.
The estimation of unsteady parameters in two-phase condition is crucial for the safety and reliability of the hydraulic systems. There are plenty of one-dimensional (1D) simulation tools for unsteady flow estimation being some of them able to present good results in monophasic flows, while almost all of them are not suitable for two-phase flows. In this research, an experimental apparatus including valves, pipes and an air vessel is used to fulfil the experiments. A mathematical formulation and a two-dimensional computational fluid dynamics (2D CFD) model have been used to predict the extreme conditions. Results show that 1D model is able to predict pressure values with acceptable accuracy. However, the 2D CFD model can be used to detect the specialized problems in a system by providing very high range of the information. © BHR Group 2018 Pressure Surges 13
Computational fluid dynamics for sub-atmospheric pressure analysis in pipe drainage
(Taylor and Francis Ltd., 2019) Besharat M.; Coronado Hernández, Óscar Enrique; Fuertes Miquel, Vicente S.; Viseu M.T.; Ramos H.M.
The occurrence of sub-atmospheric pressure in the drainage of pipelines containing an air pocket has been known as a major cause of several serious problems. Accordingly, some system malfunction and pipe buckling events have been reported in the literature. This case has been studied experimentally and numerically in the current research considering objectives for a better understanding of: (i) the emptying process, (ii) the main parameters influencing the drainage, and (iii) the air-water interface deformation. Also, this research demonstrates the ability of a computational fluid dynamic (CFD) model in the simulation of this event. The effects of the air pocket size, the percentage and the time of valve opening on the pressure variation have been studied. Results show the pipeline drainage mostly occurs due to backflow air intrusion. The worst case scenario is associated with a fast valve opening when a tiny air pocket exists in the pipeline. © 2019, © 2019 International Association for Hydro-Environment Engineering and Research.