Pressurized pipelines are crucial in various hydraulic engineering applications, including urban supply systems and hydroelectric power plants. Despite design and operational techniques advancements, these systems remain susceptible to conditions that can compromise their integrity. One significant issue is the entrapment of air within the pipes. This reduces the available cross-sectional area for water flow and can lead to critical pressure surges or sub-atmospheric pressures, particularly during operations such as filling or emptying the pipeline.
These scenarios result in hydraulic transient phenomena, which can be complex to analyze when water–air interactions are involved. The flow's multiphase nature and the air's nonlinear response to changes in volume and pressure necessitate accurate simulation models. In practice, one-dimensional models are often used due to their computational efficiency. The rigid water column (RWC) and elastic water column (EWC) approaches are the most representative, balancing physical accuracy and computational practicality. The RWC model neglects propagation and elastic effects, while the EWC model incorporates these factors, enabling a more detailed analysis of transient behavior.
This research aims to evaluate the most commonly used techniques and models for studying transient phenomena associated with pipeline emptying operations to identify advances and challenges in this field. The bibliographic review revealed that, although EWC models have been widely applied to filling processes or water hammer studies, their application in simulating pressurized pipeline emptying is rare. Consequently, there is a notable gap in the scientific literature concerning the use of models that consider the elasticity of both water and pipeline walls during these operations. This gap underscores the need to develop more comprehensive models that consider the hydrodynamic behavior of water–air interactions and the structural response of pipe walls. Such models would enhance our ability to accurately predict transient responses during emptying operations, thereby ensuring safer and more reliable management of pipeline systems.
