Dimensionless groups governing response of steel catenary risers

Steel catenary risers (SCRs) are one of the most cost effective types of risers in deep water, but their design, particularly in the touchdown zone (TDZ), is challenging. Design uncertainties arise due to limited understanding of the influence of various parameters on the SCR response, pertaining to the SCR geometry and structural properties, environmental loading and the seabed characteristics. An improved framework that provides quantitative guidance on how each parameter affects the overall structural response, and in particular fatigue damage in the touchdown zone, would facilitate design and increase confidence in the use of SCRs. This paper details the application of dimensional analysis to SCR behaviour. Suitable dimensionless groups are proposed and validated through a series of numerical tests, comparing the response of similar SCR systems defined by appropriate scaling of parameters. Due to the fundamental effect of the seabed response on fatigue damage, two types of soil models are considered in the study: a linear and a nonlinear model. The study provides a framework for design of SCRs, facilitating sensitivity analyses, enabling better control on parameters and reducing the number of simulations required.