Development of Two-Phase Flow-Induced Vibration Predicting Method for a Piping System With Elbows

Abstract Gas-liquid intermittent two-phase flow in the piping system may cause piping vibration due to the repeating collision of liquid chunk onto the inner wall of elbow fittings. To design and monitor of piping system with elbows in Oil & Gas production plants or chemical plants, it is necessary to develop a prediction method for unsteady two-phase flow in the piping, vibration of the piping and the piping fatigue strength. Several cases of unsteady two-phase flow Computational Fluid Dynamics (CFD) analysis were conducted to calculate excitation forces at each elbow of a jumper piping. In a slugging condition, the intermitted two-phase flow was simulated in CFD analysis and the frequency characteristics of fluid excitation force were obtained. Conducting the vibration analysis, the stress at each section was evaluated and the maximum stress in a slugging velocity condition was larger than that in other velocity conditions such as bubbly flow condition and stratified flow condition. Fatigue analysis in frequency domain was carried out to estimate the lifetime of elbow fittings, using the stress response spectrum in each elbow estimated by the vibration analysis. Through these analyses, it is confirmed that the developed analysis method can predict the two-phase flow and vibration characteristics which are qualitatively expected in advance.