Six-DOF simulations of an underwater vehicle undergoing straight line and steady turning manoeuvres

This paper reports on numerical simulations conducted on an underwater vehicle for six-degrees of freedom (6-DOF) free running manoeuvres using Computational Fluid Dynamics (CFD). The CFD manoeuvring trials (straight line and steady turning manoeuvres) were conducted using a model-scaled BB2 submarine with movable control planes and a body force propeller represented by an actuator disk incorporating predetermined propulsion properties. The propulsion properties were obtained from captive self-propulsion simulation adopting the actual BB2 propeller. The free running simulations were validated against experimental data. The results showed that the 6-DOF CFD simulations are capable of predicting the BB2 manoeuvring characteristics with good agreement against the experimental data. The 6-DOF manoeuvring simulations carried out allow for the unsteady viscosity effects, which is usually a limitation of the traditional coefficient-based prediction method. The simulations will enable accurate determination of the vehicle's manoeuvring characteristics, which are essential for the control system design and its safe operating envelope.