Quantification of Hydrodynamic Forces due to Torsional and Axial Vibrations in Ship Propellers

CFD is used to compute the hydrodynamic coefficients for torsional and axial vibrations, for one type of the Wageningen B-series of ship propellers in open-water condition. It is shown that the wakes shed from the blades have an influence on the magnitude and the phase of the damping forces. The dependency on reduced frequency of the vibratory motion is explained. This phenomenon can be related to the lift deficiency of trailing vortices in the wake of an oscillating plate, as derived by Theodorsen and Von Kármán and Sears, and is frequently overlooked by more recent investigations. Results of the calculations are compared with theoretical and experimental data from literature.