CFD simulations and experiments of a maneuvering generic submarine and prognosis for simulation of near surface operation

This paper presents simulations and experiments of the generic submarine Joubert BB2 in self-propulsion and free running maneuvering conditions. The free sailing experiments, performed at MARIN, include self-propulsion near the surface and at depth, turning circles, vertical and horizontal zigzag maneuvers at depth, and rise maneuvers to the surface with stops by crashback. In all cases an autopilot is used with a vertical command to control pitch and depth, and a horizontal command to control yaw and sway. These free running experiments are unique in that they present an open dataset for the community to benchmark maneuvering prediction methodologies. Computations are performed with two very different codes (ReFRESCO unstructured, REX structured overset) and consist of self-propulsion simulations at 8, 10 and 12 knots fixed at even keel and free sailing at depth, and with vertical control near the surface, a 20 degree turning maneuver with vertical control commanding the stern planes, a 20/20 zigzag maneuver with vertical control commanding both sail and stern planes, and a 20 degree rise maneuver with horizontal control, all these last at 10 knots. The results show that CFD can predict self-propulsion factors well within 5%, and that for free sailing conditions motions and speeds are well predicted, but controller commands are harder to replicate. Computations of near-surface self-propulsion and the rise maneuver with surfacing compare well with experiments and show that CFD is capable of studying submarine operation at periscope depth. Maneuvering near the surface in calm water and in the presence of waves, however, may present unique challenges that cannot be assessed with the current set of simulations.