Combined damping model for dynamics and stability of a pipe conveying two-phase flow

Vibration of a pipe conveying two-phase flow is a major concern in ocean engineering, and it is necessary to formulate a proper damping model to avoid excessive flow-induced vibration in pipes. While only a few studies have investigated the effects of damping model on dynamics of pipe conveying flow, in this work, we focus on the dynamic behavior of pipe induced by the gas-liquid two-phase flow using a combined damping model. The Generalized Integral Transform Technique (GITT) is employed to model the dynamic behavior of the pipe conveying two-phase flow, and the governing equation of vibration is transformed into a coupled system of second order ordinary differential equations in the time domain by GITT method. Parametric studies are performed to investigate the effects of damping ratios on the dynamic behavior of the pipe, and the results from this model have been verified against the existing experimental results. Besides, the dimensionless critical frequency of the pipe at which instability sets in has been predicted both in the real and imaginary part. Finally, a dimensionless structural parameter gamma(0) that can govern the normalized stability envelope of the pipe is obtained. The proposed model for the dynamics of the pipe conveying two-phase flow with combined damping can be an important reference for the design and analysis of deepwater risers.