Hydrodynamic interactions of two AUVs cruising in close proximity: The potential for enhanced energetic efficiency amid significant stability challenges

As the demand for greater operational efficiency in autonomous underwater vehicles (AUVs) grows, utilizing multiple AUVs in coordinated operations has emerged as a promising strategy. However, operating AUVs in groups presents numerous challenges, particularly regarding hydrodynamic interactions that occur when AUVs are cruising in close proximity. This study experimentally investigates these interactions during self-propelled cruising between two AUVs, using two full-scaled towing AUV models. We measure the forces acting on each AUV in various group formations by underwater force sensors. Results indicate significant changes in propulsion efficiency and stability due to these interactions: diagonal group formations can yield energy savings of up to 20% to the group, while side-by-side configurations can increase energy consumption by up to 20% to the group. Additionally, lateral forces and torques can severely destabilize AUVs, complicating group operations. This research provides valuable insights for optimizing AUV formations to enhance operational efficiency, revealing that while optimizing AUV energy efficiency through formation holds great promise, it is essential to address significant challenges related to stability.