Contribuições para a otimização do posicionamento de suportes na mitigação de vibrações induzidas por vórtices em dutos rígidos submarinos em vãos livres

Abstract

Subsea rigid pipelines are essential for hydrocarbon flow in offshore exploration. However, free spans caused by seabed irregularities and exposed to environmental loads pose a significant risk to pipeline structural integrity, potentially resulting in fatigue failure induced by vortex-induced vibrations (VIV). To mitigate these effects, periodic inspections assess the need for interventions, such as the installation of supports. However, selecting a solution must balance cost and effectiveness, requiring numerical simulations based on the Finite Element Method, following the DNV-RP-F105 recommended practice. This study proposes an optimization strategy for positioning supports in free spans of subsea pipelines to mitigate VIV. The approach employs an objective function representing the cost associated with support installation, where each free span can have a distinct penalty factor. Additionally, a constraint based on the structure’s first natural frequency is considered. The methodology involves developing and validating a simplified numerical model for analyzing natural frequencies and vibration modes and exploring different soil modeling approaches (discrete and continuous elastic foundations) and boundary conditions. Additionally, a discrete optimization module is integrated into the model, applying metaheuristic (genetic algorithm) or deterministic (branch-and-bound algorithm) optimization techniques. The results highlight the efficiency of the proposed strategy, emphasizing the performance of the branch-and-bound algorithm, which achieves optimal support positioning with fewer objective function evaluations and without randomness in the search process.