Prediction of Liquid Film Development and Erosion-Corrosion Risk in Elbowed Pipeline Systems

Erosion-corrosion in refining and chemical plant pipelines remains a persistent integrity concern, particularly in straight sections located downstream of elbows, which are rarely prioritized in inspection programs that typically focus on elbows and tees despite their well-known vulnerability. In these downstream regions, developing flow structures can sustain wall impingement and liquid film formation, leading to progressive material loss that is often underestimated in practice. This work examines a representative industrial pipeline through a combined approach based on computational fluid dynamics (CFD) simulations and controlled experimental validation to resolve the hydrodynamic behavior in the straight pipe section downstream of an elbow under different operating conditions. The objective is to identify the governing parameters controlling liquid film development and to support predictive assessment of erosion-corrosion risk in overlooked pipeline regions. The analysis shows that liquid film length is primarily controlled by flow velocity, water volume fraction, and the length of the upstream vertical section. When the upstream vertical pipe length is below 1 m, the flow remains highly unstable after the elbow, promoting intensified wall interaction and increased erosion susceptibility. For larger upstream lengths, the liquid film length exhibits an approximately linear increase with water volume fraction. Its dependence on flow velocity is non-monotonic, increasing at lower velocities, reaching a maximum at 6 m/s, and decreasing thereafter. Building on these trends, a predictive correlation is developed for liquid film length as a function of water volume fraction, flow velocity, and pipe length. The resulting model provides a quantitative basis for identifying erosion-corrosion risk in straight pipe sections and supports more targeted inspection and integrity management strategies in industrial pipeline systems.