The effects of hull pitching motions and waves on periodic propeller blade loads

You are here: Homepage > Search

The effects of hull pitching motions and waves on periodic propeller blade loads

Jessup, S.D. / Boswell, R.J.

Fundamental investigations were made of the effects of periodic hull pitching motions and waves on the periodic loads on propeller blades and bearings. These periodic loads were measured during carefully controlled model experiments in which the periodic hull pitching motions, regular waves, and relative phase of the hull pitching to the wave encounter were systematically and independently varied. The periodic blade loads were calculated using trochoidal wave velocity profiles, and representation of the propeller based on a quasi-steady method. The results of both theory and experiment show significant modulation of the amplitudes of the periodic blade loads with hull pitching motions and wave frequency of encounter. The influence of the hull significantly modifies the amount of modulation of the shaft frequency loads due to both the periodic vertical motion of the propeller and the trochoidal wave velocity profile in the absence of the hull. Therefore, for engineering purposes, the modulation of blade loads due to waves and hull motions for transom type hulls can be estimated by simple trochoidal wave velocity profiles, quasi-steady propeller theory, and constant multiplies derived from the experiments presented in this paper.