Model Tests on Hydrodynamics of Propeller Blade Vibrations

Abstract

By means of a specially designed propeller drive, steady vibrations of the propeller hub were generated, at constant advance speed and shaft rotation. By changing the frequency, resonance with blade vibrations could be realized. These tests have been performed for a non- rotating propeller in air and in water. Also, for the propeller operating in a homogeneous flow such a test has been performed. By measuring the blade response, information of the resonance frequency and information about added mass of water and hydrodynamic damping is obtained. It is shown, that, although the damping is clearly present , still an appreciable magnification of the blade vibrations at resonance will occur. Whereas close to or at resonance operation for large diameter, wide blade or highly skewed propellers is possible, these results have to be seriously accounted for when designing such propellers.