Semi-analytical solution for soil-constrained vibration of subsea free-spanning pipelines

Apart from being induced by internal and external flow, vibration of free-spanning pipelines is also constrained by the soil that supports the span on both ends. A wake oscillator model is chosen to describe the vortex shedding acting on the pipeline, and the soil spring is adopted to describe the pipe-soil interaction at the span shoulders. A semi-analytical solution - the generalised integral transform technique (GITT)-is used to study the dynamic response of free-spanning submarine pipelines. With this method, the coupled fluid-structure system of partial differential equations is transformed into a system of second-order ordinary differential equations in temporal variable. Parametric studies are carried out to analyse the influence of different internal and external flow velocities, and different soil stiffness. GITT is proved to be a fast and accurate approach for analysing the dynamic response of free-spanning submarine pipelines considering the influence of the current and the internal flow, as well as the effect of the soil.