Abstract
The study of draining processes without admitting air has been conducted using only steady friction formulations in the implementation of governing equations. However, this hydraulic event involves transitions from laminar to turbulent flow, and vice versa, because of the changes in water velocity. In this sense, this research improves the current mathematical model considering unsteady friction models. An experimental facility composed by a 4.36 m long methacrylate pipe was configured, and measurements of air pocket pressure oscillations were recorded. The mathematical model was performed using steady and unsteady friction models. Comparisons between measured and computed air pocket pressure patterns indicated that unsteady friction models slightly improve the results compared to steady friction models.
Highlights
Mathematical models have been proposed for simulating draining and filling operations [1] in water installations
Analyzed the implications of a rapid filling operation in bypass water pipelines; Vasconcelos et al [8] studied the pressure surges in stormwater tunnels; Izquierdo et al [9] analyzed the influence of a trapped air pocket in a water installation of irregular profile; Laanearu et al [10,11] proposed a semi-empirical model for analyzing a draining operation; and Fuertes-Miquel et al [3] and Coronado-Hernández et al [12] proposed a mathematical model for studying the emptying operation in water pipelines
The draining process was analyzed considering steady and unsteady friction models in order to note the effect on the accuracy of the current one-dimensional mathematical models for simulating this operation
Summary
Mathematical models have been proposed for simulating draining and filling operations [1] in water installations. These hydraulic events can cause dangerous pressure surges for filling processes and sudden drops in sub-atmospheric pressure during draining operations, depending on the magnitude of air pocket volumetric changes and the characteristics of water pipelines [2,3,4]. The complexity of these phenomena involves the study of governing equations for the water column, the polytropic law of entrapped air pockets, and the air–water interface formulation [5,6]. Analyzed the implications of a rapid filling operation in bypass water pipelines; Vasconcelos et al [8] studied the pressure surges in stormwater tunnels; Izquierdo et al [9] analyzed the influence of a trapped air pocket in a water installation of irregular profile; Laanearu et al [10,11] proposed a semi-empirical model for analyzing a draining operation; and Fuertes-Miquel et al [3] and Coronado-Hernández et al [12] proposed a mathematical model for studying the emptying operation in water pipelines.
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