Abstract
Inertial models have been used by researchers to simulate the draining and filling processes in water pipelines, based on the evolution of the main hydraulic and thermodynamic variables. These models use complex differential equations, which are solved using advanced numerical codes. In this study, a quasi-static flow model is developed to study these operations in hydraulic installations. The quasi-static flow model represents a simplified formulation compared with inertial flow models, in which its numerical resolution is easier because only algebraic equations must be addressed. Experimental measurements of air pocket pressure patterns were conducted in a 4.36 m long single pipeline with an internal diameter of 42 mm. Comparisons between measured and computed air pocket pressure oscillations indicate how the quasi-static flow model can predict extreme values of air pocket pressure for experimental runs, demonstrating the possibility of selecting stiffness and pipe classes in actual pipelines using this model. Two case studies were analysed to determine the behaviour of the quasi-static flow model in large water pipelines.
Highlights
The interaction of water columns with entrapped air pockets in water pipelines is difficult to understand because hydraulic and thermodynamic formulations need to be analysed [1,2]
This study focuses on the behaviour of draining and filling processes in water pipelines using the quasi-static flow model, which represents a simplified formulation regarding the elastic model and the mass oscillation equation [20,21]
A new one-dimensional mathematical model was developed compute the main hydraulic thermodynamic variables during draining and filling processestowith an entrapped hydraulic and thermodynamic variables during draining and filling processes with an entrapped air air pocket in water installations, which was based on the quasi-static flow model, the polytropic pocket in water installations, wasflow based on the quasi-static flow model, the polytropic formulation of an air pocket andwhich the piston model to represent the air–water interface
Summary
The interaction of water columns with entrapped air pockets in water pipelines is difficult to understand because hydraulic and thermodynamic formulations need to be analysed [1,2]. The analysis of the abovementioned hydraulic events is critical as a filling process is characterised by the rapid compression of an air pocket, which produces pressure surges [4,7], and a draining manoeuvre produces a sub-atmospheric pressure condition owing to the expansion of air pockets [9,11,12] Both processes should be carefully performed to prevent the risk of water installation collapse. This study focuses on the behaviour of draining and filling processes in water pipelines using the quasi-static flow model, which represents a simplified formulation regarding the elastic model and the mass oscillation equation [20,21]. Results show that the quasi-static flow model can be used to simulate draining and filling processes in water pipelines, as comparisons between computed and measured extreme values of air pocket pressure indicate their adjustment. The quasi-static flow model is compared with an inertial model for two case studies (one corresponds to a draining process and the other to a filling operation) to show how extreme values of analysed variables are simulated for the quasi-static flow model
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