Effect of slug flow frequency on the mechanical stress behavior of pipelines

Highlights: • Interaction between the slug two phase flow and the pipe wall was investigated experimentally. • The effect of slug frequency on the induced stresses was addressed. • The stress signals were processed using Rainflow cycle counting method. • A validated Slug Frequency Stress Prediction Model (SFSPM) was developed. -- Abstract: Slug flow is a prevalent and undesirable multiphase flow regime which occurs in many industrial processes, causing time varying stresses in pipes and supports and consequently causes structural fatigue damage and failure. In this study, a series of experimental tests were conducted to address the effect of the slug frequency on the stresses of structural pipes. The slug frequency was measured using non-intrusive measuring technique through utilizing Phantom 9.1 high speed camera, while the pipe wall strain was captured using bi-axial strain gauges. The effects of the superficial gas and liquid velocities on the slug frequency were investigated. Additionally, the relation between the slug frequency and the induced stresses was examined. Moreover, a Slug Frequency Stress Prediction Model (SFSPM) based on the exerted slug unit forces was developed and validated. The presented results revealed that an excellent correlation with a deviation of 0.7% between the predicted and experimental stresses was achieved.