Study On The Multi-objective Optimization Design Of The Cross-sectional Layout Of The Marine Umbilical

As a key device in subsea production system of the offshore hydrocarbon resources exploitation,the umbilical consists of a variety of functional components such as hydraulic tubes,electrical cables and optical cables.The mechanical properties of these functional components are very different.Different layout forms of components make the umbilical show different geometric and mechanical properties.Under the action of external load,unreasonable cross-sectional layout may lead to large deformation and contact pressure between components,thereby affecting the service life of an umbilical.The cross-sectional layout design is one of the key steps in the umbilical design process.Therefore,how to design the cross-sectional layout to improve the ability and service life of the umbilical to withstand various loads in the ocean during service is a very necessary research work.The existing design specifications require that the cross-sectional layout design of an umbilical should follow the principles of symmetry and compactness.However,there is no specific executable method which brings many difficulties and challenges to the cross-sectional layout design.Firstly,the quantifiable operation index is given and the corresponding multiobjective optimization model is established considering the principle of minimizing the contact pressure between vulnerable components such as steel pipes based on the requirements of the specification in this paper.Furthermore,the minimum enclosing circle algorithm for the cross-sectional layout is developed,and the manufacture factor is considered and the layering strategy based on the identification of contact points is introduced.After establishing the optimization model,firstly,the optimization model is solved based on the generalized multiplier method and the optimal cross-sectional layout of an umbilical is obtained.In order to overcome the disadvantage that the generalized multiplier method can not guarantee the global optimization due to relying on the initial value,then the genetic algorithm is carried out to solve it.In the meanwhile,the selection operation in the genetic algorithm is revised to strengthen its ability to find the best in local areas.Finally,in order to quickly obtain the section lay out design under the condition of ensuring the global optimal solution,the GA-GLM optimization algorithm combined with the advantages of generalized multiplier method and genetic algorithm is developed.The optimization design process of the cross-sectional layout is redesigned and the cross-sectional layout form with better geometric and mechanical properties is obtained.In order to verify the correctness of the cross-sectional layout problem solved by the generalized multiplier method,genetic algorithm and GA-GLM algorithm,the finite element models of umbilical crosssections with different layout forms obtained by the algorithm are established respectively to analyze structural mechanical properties,and the optimal cross-sectional layout is determined.By comparing and analyzing the performance of the algorithm,it is found that GA-GLM algorithm has better applicability in solving the problem of the cross-sectional layout of an umbilical.The algorithm is applied to the situation of multi-component and multi-layer arrangement of the cross-section.In addition,in order to avoid the large vacancy of crosssection layout due to the influence of the number of components,the design method of automatic filling is introduced,and the optimal cross-section layout of umbilical cord is obtained.The research achievements of this paper supply a specific way for the cross-sectional layout design of an umbilical which will help to improve the independent design and innovation ability in the deep-sea oil and gas development equipment industry for China,and has certain engineering application value.