Dependence of tip and hub vortices shed by a propeller with winglets on its load conditions

Abstract

Large-eddy simulation on a cylindrical grid consisting of about 5 × 109 points is utilized to reproduce the wake of a five-bladed propeller with pressure side winglets. Computations are conducted across five values of the advance coefficient, to capture the dependence of the tip and hub vortices on the rotational speed of the propeller. The results demonstrate that the pressure minima at the core of all vortices grow more quickly than the rotational speed of the propeller, making them more problematic in terms of cavitation phenomena, acoustic signature, and stresses. Also, the instability of both tip and hub vortices is captured. It develops more quickly for increasing rotational speeds and is faster for the tip vortices than for the hub vortex, as demonstrated by the streamwise evolution of turbulent kinetic energy at the their core, which is non-monotonic: the initial decline of turbulence after the onset of both tip and hub vortices is followed by a rise, due to instability. This switch occurs faster at the core of the tip vortices than within the hub vortex.