Hydrodynamic Analysis of Two AUVs in Tandem: Influence of Appendages and Spacing

The formation operation of Autonomous Underwater Vehicles (AUVs) generates complex hydrodynamic interactions, significantly impacting the performance and maneuverability of submarines. This study employs Computational Fluid Dynamics (CFD) to analyze the hydrodynamic interactions between two AUVs arranged in tandem, investigating the effects of spacing and appendages on drag. First, the calculated drag results of submarine models, with and without appendages, at various speeds were compared with experimental data, validating the accuracy of the numerical methods used in this study. Four configuration combinations were designed for the study. Analysis of drag, pressure distribution, and velocity fields reveals that both the spacing between AUVs and the presence of appendages significantly affect total drag. At closer distances, the rear of the leader AUV experiences partial pressure recovery, which helps reduce pressure drag, leading to substantial drag reduction, with a maximum reduction of 8.34%. Additionally, due to the wake shielding effect, the friction drag on the follower AUV is significantly reduced, with a maximum reduction of 14.1%, thereby decreasing the total drag. The presence of appendages causes noticeable flow separation and wake interference, limiting the potential drag benefits.