Curvature effect on wet collapse behaviours of flexible risers subjected to hydro-static pressure

Flexible risers that for deep-water production are designed with strong collapse capacity. However, this collapse capacity is susceptible to pipe curvature in the flooded annulus condition. For the curved riser sections within the touchdown zone, significant reduction of collapse capacity can occur once the external sheaths are worn out, resulting in the so-called ‘wet collapse’. Therefore, the collapse capacity of flexible risers should be well-determined during design stage. Mostly, curved collapse analyses are performed through costly numerical simulations since there is no well-established analytical models . This study focuses on the wet collapse mechanism of curved flexible risers, aiming to pave the way for the development of analytical solutions. 3D full FE models were adopted to gain insight into the wet collapse mechanism of curved risers, which had been verified by the data from public literature. The investigation indicates that the deformed cross-sectional shape of the carcass is the dominant factor of the curvature effect.