Dynamics of cantilevered piping system conveying two-phase flow

This work explores the dynamics of two-phase flow in cantilevered pipes, emphasizing the role of flow pattern transitions in system stability. A unified model that couples flow parameters with the vibration equation is established, grounded in a precise slug flow model and regime transition conditions. The equations are discretized via the Galerkin method, and the 4th-order Runge–Kutta serves to solve for the nonlinear dynamic responses. Validation of the model is conducted using experimental data and published results and compared with the improved drift flux model (DFM). Theoretical analysis indicates that the critical flutter velocity predicted by DFM is lower than that of the slug dynamics model. When superficial gas velocity increases and flow pattern transitions to annular flow, DFM fails to predict the restabilization caused by redistribution of flow velocity and liquid holdup. Under DFM, with superficial liquid velocity as the variable, an instability–restabilization–instability pattern is observed. Thus, DFM reliability is questionable under flow patterns with weak interfacial interaction. Nonlinear analysis shows that both models exhibit flutter instability with periodic motion. The effect of dissipation on stability is mass-dependent: to a certain extent, dissipation enhances stability, but when the dimensionless mass exceeds a critical value, it causes negative effects.