Hydrodynamic loads and wake dynamics of a propeller working in oblique flow

Abstract

Most of the small crafts and navy ships are equipped with propellers mounted on inclined shafts as thrusters. In spite of its importance, the information on the forces generated by inclined shaft propellers is scarce. To help the designers of small craft and navy ships, the present research describes a systematic numerical program undertaken to evaluate the propeller performances when inclined in respect to the oncoming flow. Scale resolved incompressible Detached Eddy Simulation (DES hereafter) or Delayed Detached Eddy Simulation (DDES) technique are employed by using a volume of fluid approach to study the four-blade propeller recommended in 2015 Tokyo Workshop on CFD Ship Hydrodynamics for the ONR tumblehome ship model 5613. A series of three working conditions are numerically analyzed over a range of shaft inclinations and advance coefficients. Besides, the usual shaftline thrust and torque, horizontal and vertical side forces are computed. The results of these simulations confirm the expectations that a propeller mounted on an inclined shaft produces less thrust than the same propeller on a horizontal shaft. This paper contains propeller characteristic curves and lift- and side-force data which are directly applicable in the design of both high-performance small craft and commercial ships.