Analysis of wake around DARPA Suboff including self-propulsion with a seven-blade propeller in positive pitches

The Delayed Detached Eddy Simulation(DDES) of the DARPA Suboff, including self-propulsion with sail, fins and seven-blade propeller, is performed at high Reynolds number and pitch-angle inflow besed OpenFOAM, the mixing evolution and energy performance of the vortex structure have been focused. Computations of Suboff are validated against reference data, simulation and experiment of the propeller are carried out simultaneously under the condition of high blade load (J = 0). The time-averaged, phase-averaged, instantaneous vorticity fields and power spectral density (PSD) around the submarine including self-propulsion, are reported under oblique inflow with drift angles of 0°, 7° and 15°. Computations demonstrate that the oblique inflow will deflect and attenuate the horseshoe vortex behind the sail resulting in no longer interacting with fin. Besides, it will speed up the process of the vortex dissipation to a certain extent. With the increase of inflow angle, the hydrodynamic performance of the propeller will have an increasing trend, but the trend will decrease. The fin-sheet vortex accelerates the instability process of the leeward wake, moreover, the horizontal fin-sheet vortex and propeller wake will deflect leeward with the inflow-angle increasing, varying the area of interaction. It is worth noting that the tip-vortex induced by leeward fin is attracted to wake, resulting in the abnormal wake under 15° inflow, and drift opposite to the rotation direction of the propeller.