Consideration on Propeller Damping in Torsional Vibration of Recent Propulsion System

Abstract

Propeller damping has decreased in recent vessels with the decrease of engine mass and propeller pitch ratio, adoption of aft engine for cargo efficiency, etc., accordingly its rate to the whole damping has also decreased.
For the above reasons, traditional methods by Wilson et al. which consider propeller damping alone, estimate vibration amplitude and stress too much and make so much error.
So to get higher exactness the authors examined records and carried out calculation depending upon the enercv theory which treats rightly propeller damping.
As a result of the examination an exact formula for the amplitude of one node vibration was developed as follows:
θ=D²rT_nΣaF(0.315+0.1a_p)/9.55×10³i²Hαa_p² (rad)