Investigation on Hydrodynamic Performance of the Integrated Propulsor Under Crashback Modes

For safety of the ship manoeuvring and propulsor operating, crashback condition is of great concern because of the complicated nonlinear flow resulted from rotating the propellers in reverse while the vehicle is moving forward. The hydrodynamic performance of the integrated propulsor under crashback condition is drawing much attention for its wide application on underwater vehicles. In this paper, the feasibility of a Reynolds-Averaged Navier-Stokes equations (RANS) method for study of flow characteristics around the propulsors and underwater vehicles is firstly verified by its predicted results in good agreements with experimental values. Then, comparative analysis of open-water performance and flow field details is conducted between three configurations (single propeller, propeller with pre-stator, propeller with pre-stator and duct, respectively) to distinguish their effects on flow field characteristics around the propulsor under forward and crashback conditions. Finally, the dynamic numerical simulation for the axial motion of the underwater vehicle is performed using overset grid technique to predict the hydrodynamic load and the complicated flow field around its integrated propulsor during the process when the propulsor rotation transfers from positive to negative speed. The formation and development of the vertex ring are observed and analyzed.