Novel Bio-inspired Design for the Carcass Layer of Flexible Risers with Increased Strength Under External Pressure

Abstract

Flexible risers are crucial pieces of equipment for moving output fluids from wells to platforms during the extraction of oil and gas from deep-sea resources. One of the causes of collapse in these pipes is the high hydrostatic pressure applied to risers in deep water. The innermost layer of a riser, known as the carcass layer, plays a critical role in resistance to external pressure. In this study, we investigated the collapse (nonlinear buckling) of a riser under external pressure, and a novel design based on the structure of a beetle’s exoskeleton was used to increase the load capacity of the carcass layer. This type of beetle skeleton is constructed in such a way that it creates strong connections among the various parts of the external skeleton to considerably enhance strength against external pressure while allowing necessary movements. To assess the performance of the design in comparison with the original design, we examined the nonlinear buckling of the new structure under external pressure. Through genetic algorithm optimization, design parameters were obtained, and the maximum strength before collapse was determined. Results show that the critical pressure in the new design substantially increases relative to that in the original design.