Six-DOF motion response and manoeuvring simulation of an underwater vehicle

This thesis presents the development of a validated six Degrees-of-Freedom (6-DOF) manoeuvring simulations of a fully appended BB2 generic submarine using Computational Fluid Dynamics (CFD). A build-up approach is used to first investigate the hydrodynamics of the vehicle's subcomponents individually, starting with the bare hull and propulsor models (i.e. a body force model and rotating model), progressing to the fully appended configuration for 6-DOF simulations that includes the hull, forward and aft control surfaces and a body force propeller. The bare hull study involved prescribed motions (i.e. straight line, pure sway, and pure yaw) to examine the capability of the CFD model to predict the hydrodynamic forces and moments acting on the hull. The CFD predictions are validated, with good agreement, against experimental captive model measurements obtained at the Australian Maritime College Towing Tank (AMCTT). The propeller study involved hydrodynamic characterisation of a marine propeller operating in an open water condition. The global field quantities at various advance speeds are predicted using the CFD model, which were validated against experimental measurements provided by the Australian Maritime College Cavitation Research Laboratory (AMC CRL). Finally, the 6-DOF manoeuvring simulation study involves three generic manoeuvring tests (i.e. a straight line, steady turning and zig-zag manoeuvres) with a body force propeller and movable control planes commanded by an autopilot. The CFD predictions are validated against experimental free running measurements provided byMaritime Research Institute Netherlands (MARIN), showing that the 6-DOF manoeuvring CFD model is able to predict the vehicle`s trajectory and speeds with reasonable accuracy. The developed CFD model and its methodology presented in this thesis can be used by underwater vehicle designers to carry out 6-DOF manoeuvring simulations for various vehicle designs, configurations and missions. The capability of 6-DOF manoeuvring simulations will enable the designers to determine a vehicle's manoeuvring characteristics for control system design and its safe operational limits.