Analysis of the impact of steady slug flow on the dynamic response of a steel catenary riser

Abstract

The transient excitation caused by the non-uniform mass distribution of steady slug flow in an offshore riser can lead to structural vibration. To predict riser response due to slug flow using nonlinear time-domain analyses, a finite element model of riser-slug coupling is developed in this study. The model combines the absolute nodal coordinate formula and the arbitrary Lagrangian-Eulerian description. The proposed method has the ability to effectively simulate both the non-uniform mass distribution of slug flow and the geometric nonlinearity of the riser, thus avoiding a complex coordinate transformation of the elements. A type of steel catenary riser with an internal flow is taken as an example to discuss the effect of steady slug flow. The results show that, compared with the uniform flow, slug flow can result in a larger local deformation of the riser. The length of the slug has a significant effect on the bending moment of the touchdown zone.