  In this study, the ducted propeller has been numerically investigated under
oblique flow, which is crucial and challenging for the design and safe
operation of thruster driven vessel and dynamic positioning (DP) system. A
Reynolds-Averaged Navier-Stokes (RANS) model has been first evaluated in the
quasi-steady investigation on a single ducted propeller operating in open water
condition, and then a hybrid RANS/LES model is adapted for the transient
sliding mesh computations. A representative test geometry considered here is a
marine model thruster which is discretized with structured hexahedral cells,
and the gap between the blade tip and nozzle is carefully meshed to capture the
flow dynamics. The computational results are assessed by a systematic grid
convergence study and compared with the available experimental data. As a part
of novel contribution, multiple incidence angles from $15^\circ$ to $60^\circ$
have been analyzed with varying advance coefficients. The main emphasis has
been placed on the hydrodynamic loads that act on the propeller blades and
nozzle as well as their variation with different configurations. The results
reveal that while the nozzle absorbs much effort from the oblique flow, the
imbalance between blades at different positions is still noticeable. Such
unbalance flow dynamics on the blades and the nozzle has a direct implication
on the variation of thrust and torque of a marine thruster.
