The purpose of this study is to investigate pressurized pipelines and the potential effects on pressure transients of air entrained at the downstream end of large entrapped air pockets followed by a hydraulic jump in pressurized pipelines. The homogeneous two-phase flow model is used to simulate the transient response of the bubbly mixture after a pump shutdown. The results show that pressure transients are significantly reduced with increasing air-pocket volumes and bubbly flow air content. Experimental investigations were carried out to analyze the impact of different air-pocket volumes located at high points of pressurized pipelines. A case study of an existing pumping system was considered to exemplify the impact of the bubbly flow air content on hydraulic transients.
Air in pipelines may cause insignificant to severe operational difficulties. If air pockets remain at high points of pumping pipelines, they can cause problems such as a reduction of the effective pipe cross-section, resulting in an increase of head losses. Air pockets can amplify the maximum peak pressures during transients and cause pipe failure. To study large air pockets located at high points in pumping pipelines, experimental investigations were conducted to corroborate that the flow underneath a large air pocket under pressurized flow conditions can be considered similar to gradually varied open channel flow. The hydraulic grade line at pressurized flow conditions was measured with and without air pockets in the test section of the experimental apparatus to verify its effect on the head losses.
Abstract.Results of physical model studies of water column separation following an upstream valve closure in a horizontal pipe are presented, using three dimensionless parameters: the magnitude of the transient, M, or the ratio between the Joukowsky pressure and the initial absolute head;, or the ratio between the maximum overpressure and the Joukowsky pressure, and t cr , the duration of the vapor cavity relative to the pipeline period. Conclusions are derived, aiming to a better understanding of water column separation extreme pressures and to the establishment of useful preliminary design guidelines.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.