The prediction of axial, torsional and transverse shaft vibrations of propulsion shafts in the design stage requires accurate knowledge of the hydrodynamic coefficients that describe the propeller contribution to the inertial, damping and coupling effects in the entire system.

The objective of the paper will be to describe a novel numerical procedure for determining these coefficients using a computer program based on unsteady lifting surface theory. Given a description of the propeller geometry, the output of such a method consists of a set of 24 coefficients, eight for coupled axial-torsional vibrations and sixteen for coupled transverse vibrations.

A brief description will first be given of the origin of these coefficients for a propeller vibrating in an unbounded fluid at a prescribed frequency. The paper will then show how the M.I.T. unsteady lifting surface theory computer program was modified and extended in Order to automatically compute these coefficients. Example calculations are given for a controllable pitch propeller.

The axial added mass coefficient is then chosen for detailed comparisons between empirical formulae, tests and detailed calculations. A discussion is finally given of the influence of the various assumptions, the effect of variations of the significant problem parameters and the directions in which future work must proceed to further improve the predictive capability of the developed numerical procedure.

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