Investigation of the Behavior 2D of Trapped Air in the Water Conveyance Systems During Rapid Filling or Emptying Process

Document Type : Research Paper


1 Prof., Dept. of Civil Engineering, Faculty of Engineering, Maraghe University, Maragheh, Iran

2 MSc Student in Civil and Hydraulic Structures, Faculty of Engineering, Maragheh University, Maragheh, Iran

3 Assist. Prof., Dept. of Civil Engineering, Faculty of Engineering, Maragheh University, Maragheh, Iran

4 PhD, Instituto Superior Técnico, University of Lisbon, Portugal


The trapped air in the water conveyance systems may cause the obstruction of flow, corrosion and adverse effect on the performance of valves and pumps. This study is part of the Abbas Abad Dam Drinking Water Transmission Line using Ansys Fluent Software, The behavior of air entrapped during the filling and discharging process and the effect of its existence on pressure changes were studied. Entrapped air was simulated at 0.5, 2, 3 m lengths and inlet pressures of 1.2456, 1.7456 and 2.2456 atmospheres for a 35-meter-long metal pipe with a discharge valve embedded in its outlet end. The effects of pressure-time changes were investigated in two ways: a) pressure changes in the pipe and drain valve and b) pressure changes inside the entrapped air. The results showed that the pressure changes in both cases were due to the large fluctuations in confined air and that the fluctuations continued until the drain valve was fully opened and the longer the confined air length was, the greater the amplitude and length of the created fluctuations. Modeling with similar boundary conditions without the presence of air indicates no pressure fluctuations. The results of the verification confirm the research results. Besides the Palau et al, 2019 results, calculation of relative error, RMSE and NRMSE were used in order to validate the numerical model results.


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