AUV hydrodynamics for survivability and controllability

Transient force and torque on a small Autonomous Underwater Vehicle (AUV) traversing underneath a sailing ship in deep water are quantified under idealized conditions. This study represents the ship's hull and the flow field by the lower half of the flow field associated with an axial symmetric Rankine oval. The AUV has a semi-spherical nose cone, a cylindrical body, a tapered section, and a tail-cone. Connected to the underside of the AUV is a magnetometer. The AUV and the magnetometer are represented by a two dimensional body with a profile that matches that of the AUV and the magnetometer. The flow field experienced by the AUV is essentially two dimensional and is modeled as such. Assuming potential flow with infinite extent, a panel method is used to obtain the tangential velocities on the AUV and magnetometer surfaces. Dynamic pressures at these surfaces are found using the unsteady Bernoulli equation. The force and torque are then computed. Rapid changes of these hydrodynamic loads as the AUV passes under the bow and the stern of the ship are demonstrated.