Multidisciplinary Optimization Design for the Section Layout of Umbilicals Based on Intelligent Algorithm

Umbilicals, which link top floaters and subsea devices, provide control functions through electrical cables and hydraulic remote transmission. These cables are considered the "lifeline" of subsea production systems for offshore oil and gas exploitation. Umbilicals should undertake self-weight and periodic loading during operation because of the severe conditions of the ocean environment. Heat is released to the umbilical body during power transmission in electric cables, which influences the mechanical properties and optical transmission in the cable. However, several sectional arrangements can be applied to a number of umbilical components. Thus, sectional layout design with multiple components should be treated as a multidisciplinary optimization problem. From the mechanical point of view, the umbilical structure should be designed with compact and symmetric layout to obtain an even probability of resistance to loads and reduce structural stress, thereby improving fatigue performance. In terms of thermal effect, these electric cables should be arranged to dissipate heat easily and avoid influence on functional and structural components. This study quantifies compactness, symmetry, and temperature distribution by introducing corresponding indices. A multidisciplinary optimization framework is then established. Particle swarm optimization (PSO) intelligent algorithm is adopted to perform optimization and obtain the optimal solution, which is superior to the initial design. The optimization design strategy is proven effective and efficient by a case study, which provides a reference for umbilical design.