Hydrodynamic Analysis and Optimisation of a Subsea Towed Docking Station in Variable Sea States

Abstract This study addresses the development of a subsea towed docking system for the efficient launch and recovery (L&R) of Autonomous Underwater Vehicles (AUVs). AUVs are essential in oceanographic research, commercial operations, and military applications due to their autonomy and versatility. However, the lack of a fixed attachment to their host platform during the launch and recovery process creates significant operational bottlenecks. This paper builds on prior research by proposing a Launch and Recovery Device (LARD) in form of a subsea towed docking cone. The device employs a funnel-like design for guided docking and a clamping mechanism to secure various AUVs. Towed underwater, it mitigates wave-induced motions by exploiting the attenuation of wave energy with depth. The system’s dynamic performance, modeled using OrcaFlex, incorporates a rigid-body analyses model for the transmission of ship-induced motion to the LARD through the towing cable. This requires the consideration of hydrodynamic coefficients, like additional mass and damping coefficients, which are determined on the basis of CFD simulations. Different configurations of the LARD are under investigation, focusing on achieving optimal towing performance. Future validation efforts will involve scaled experimental testing in controlled test facilities, emphasizing the system’s adaptability and reliability for enhancing AUV operations across diverse applications.