Flow-induced vibration of separated two-phase flow at flow-turning element

In this study, the fluctuating force induced by a vertical annular two-phase flow through a pipe turning element is investigated. An experiment was conducted to obtain datasets for an annular two-phase flow regime, including dynamic force signals, outer wall acceleration, pressure fluctuations, and void fraction. To develop a model for predicting the peak fluctuating force magnitude and frequency at a 90-degree turning element, a collisional force model was formulated based on the disturbance wave of annular flow. This model was derived using a local instantaneous formulation and surface wave analysis. Model assessment revealed that momentum fluctuations significantly contribute to force fluctuations in annular two-phase flow. Additionally, collisional effects arising from interactions between the inner wall surface and disturbance waves were found to play a crucial role in force fluctuations. Force spectrum analysis demonstrated that the proposed model can predict force fluctuations and dominant frequencies induced by annular flow with satisfactory accuracy. The analytical approach to identify fluctuating force behaviors in annular two-phase flow regime presented in this work provides valuable insights for analyzing flow-induced vibration phenomena in various industrial applications.