Hydrodynamic Analysis of Payload Bay Berthing for Underwater Vehicles

The development of extra-large uncrewed underwater vehicles (XLUUVs) presents an opportunity for transporting smaller uncrewed or autonomous underwater vehicles (UUV/AUVs) over long distances, within an XLUUV's payload bay, enabling energy-constrained AUVs to spend longer periods on station rather than in transit to-and-from their operational areas. Existing launch and recovery techniques for AUV platforms have focused on the use of static docks, towed docks, and surface vehicle dock recovery. This article seeks to determine the optimal approach configuration and feasibility of recovering an AUV, via an XLUUV's payload bay, while underway. Optimality was assessed via an analysis of drag, pressure, turbulence, and flow-field phenomena exerted on the AUV undertaking berthing. To make these determinations, a converged and validated computational fluid dynamics simulation was performed using ANSYS Fluent. The simulation assessed two variations to the AUV's approach: path-aligned and flow-aligned, with respect to the AUV's bow. These simulations were repeated across three different speeds and trajectories. The most optimal approach was identified to be the 1 knot, flow-aligned, high steepness trajectory. This approach correlated with reduced propulsion induced effects, more consistent lift and drag effects, and reduced turbulence intensity, kinetic energy, and vortical effects when compared with the other approaches under analysis.