Browsing by Author "Besharat M."

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A parametric sensitivity analysis of numerically modelled piston-type filling and emptying of an inclined pipeline with an air valve
(BHR Group Limited, 2018) Coronado Hernández, Óscar Enrique; Fuertes Miquel, Vicente S.; Besharat M.; Ramos H.M.
Filling and emptying operations should be planned by engineers in operational stages to prevent a system failure depending on reaching extreme low pressure values. In this sense, a compression of an air pocket produces pressure surges, while an expansion generates troughs of subatmospheric pressure. A sensitivity analysis of main hydraulic and thermodynamic parameters was conducted based on a mathematical model developed by the authors. A case study was selected to see the influence of different parameters. When the filling operation is performed, the more sensible parameters are pipe slope, air valve size, internal pipe diameter, and friction factor; while, the emptying operation shows that air valve size, air pocket size, pipe slope, and internal pipe diameter are the more sensible parameters. © 2018 BHR Group.
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.
Concerning Dynamic Effects in Pipe Systems with Two-Phase Flows: Pressure Surges, Cavitation, and Ventilation
(2022-07-31) Ramos, Helena M.; Fuertes Miquel, Vicente S.; Tasca, Elias; Coronado Hernández, Óscar Enrique; Besharat M.; Zhou, Ling; Karney, Bryan
The risks associated with unsteady two-phase flows in pressurized pipe systems must be considered both in system design and operation. To this end, this paper summarizes experimental tests and numerical analyses that highlight key aspects of unsteady two-phase flows in water pipelines. The essential dynamics of air–water interactions in unvented lines are first considered, followed by a summary of how system dynamics change when air venting is provided. System behaviour during unsteady two-phase flows is shown to be counter-intuitive, surprising, and complex. The role of air valves as protection devices is considered as is the reasonableness of the usual assumptions regarding air valve behaviour. The paper then numerically clarifies the relevance of cavitation and air valve performance to both the predicted air exchanges through any installed air valves and their role in modifying system behaviour during unsteady flows
Effect of a commercial air valve on the rapid filling of a single pipeline: A numerical and experimental analysis
(MDPI AG, 2019) Coronado Hernández, Óscar Enrique; Besharat M.; Fuertes Miquel, Vicente S.; Ramos H.M.
The filling process in water pipelines produces pressure surges caused by the compression of air pockets. In this sense, air valves should be appropriately designed to expel sufficient air to avoid pipeline failure. Recent studies concerning filling maneuvers have been addressed without considering the behavior of air valves. This work shows a mathematical model developed by the authors which is capable of simulating the main hydraulic and thermodynamic variables during filling operations under the effect of the air valve in a single pipeline, which is based on the mass oscillation equation, the air-water interface, the polytropic equation of the air phase, the air mass equation, and the air valve characterization. The mathematical model is validated in a 7.3-m-long pipeline with a 63-mm nominal diameter. A commercial air valve is positioned in the highest point of the hydraulic installation. Measurements indicate that the mathematical model can be used to simulate this phenomenon by providing good accuracy. © 2019 by the authors.
Effects of orifice sizes for uncontrolled filling processes in water pipelines
(2022-03-12) Aguirre-Mendoza, Andres M.; Paternina-Verona, Duban A.; Oyuela, Sebastian; Coronado Hernández, Óscar Enrique; Besharat M.; Fuertes Miquel, Vicente S.; Iglesias-Rey P.L.; Ramos, Helena M.
The sizing of air valves during the air expulsion phase in rapid filling processes is crucial for design purposes. Mathematical models have been developed to simulate the behaviour of air valves during filling processes for air expulsion, utilising 1D and 2D schemes. These transient events involve the presence of two fluids with different properties and behaviours (water and air). The effect of air valves under scenarios of controlled filling processes has been studied by various authors; however, the analysis of uncontrolled filling processes using air valves has not yet been considered. In this scenario, water columns reach high velocities, causing part of them to close air valves, which generates an additional peak in air pocket pressure patterns. In this research, a two-dimensional computational fluid dynamics model is developed in OpenFOAM software to simulate the studied situations.
Experimental and numerical analysis of a water emptying pipeline using different air valves
(MDPI AG, 2017) Coronado Hernández, Óscar Enrique; Fuertes Miquel, Vicente S.; Besharat M.; Ramos, H.M.
The emptying procedure is a common operation that engineers have to face in pipelines. This generates subatmospheric pressure caused by the expansion of air pockets, which can produce the collapse of the system depending on the conditions of the installation. To avoid this problem, engineers have to install air valves in pipelines. However, if air valves are not adequately designed, then the risk in pipelines continues. In this research, a mathematical model is developed to simulate an emptying process in pipelines that can be used for planning this type of operation. The one-dimensional proposed model analyzes the water phase propagation by a new rigid model and the air pockets effect using thermodynamic formulations. The proposed model is validated through measurements of the air pocket absolute pressure, the water velocity and the length of the emptying columns in an experimental facility. Results show that the proposed model can accurately predict the hydraulic characteristic variables. © 2017 by the authors.
Subatmospheric pressure in a water draining pipeline with an air pocket
(Taylor and Francis Ltd., 2018) Coronado Hernández, Óscar Enrique; Fuertes Miquel, Vicente S.; Besharat M.; Ramos H.M.
An air pocket’s behaviour inside of a pipeline during transient conditions is of great importance due to its effect on the safety of the hydraulic system and the complexity of modeling its behaviour. The emptying process from water pipelines needs more assessment because the generation of troughs of subatmospheric pressure may lead to serious damage. This research studies the air pocket parameters during an emptying process from a water pipeline. A well-equipped experimental facility was used to measure the pressure and the velocity change throughout the water emptying for different air pocket sizes and valve opening times. The phenomenon was simulated using a one-dimensional (1D) developed model based on the rigid formulation with a non-variable friction factor and a constant pipe diameter. The mathematical model shows good ability in predicting the trough of subatmospheric pressure value as the most important parameter which can affect the safety of hydraulic systems. © 2018, © 2018 Informa UK Limited, trading as Taylor & Francis Group.