| Abstract: ‘Propeller‘，the only power resource of ships, is the most important merchant naval applications for the propulsion system, which will affect the capability of the ship survivability and reliability seriously. ‘Resonance’ will oscillate the blade with greater amplitude deformation, when hydro excited force drives the propeller around a specific frequency. The effect of the water where the propeller is immersed causes a reduction in modal frequency and a modified mode shape compared with the corresponding characteristics in air. In order to avoid the resonance disasters, it will be necessary to analysis ‘Fluid-structure interface’ vibration characteristics of the propeller blade.
The major concern of this paper is to understand the problem of FSI blade vibration using 1) multi-points transient modal test were applied on the real Cu propeller for the structural and FSI modes characteristics; 2) high-order solid element were employed to build the structural FE model with the water field simulations; 3) a simple estimation method was founded that the fundamental frequency could be described quickly by an empirical formula, combined with the frequency reduction ratio λ.
It has been discovered in the paper that good agreement between FEM and tests has been achieved, and ‘strong coupling method’ was used because of the advantages of ‘quick convergence’, ‘time integration’ and ‘computational flexibility’. The empirical method, whilst giving a reasonable approximation, has the advantage of being simple and time efficient for initial design. Furthermore, the frequency reduction caused by the water is not a constant value, and the relationship will need to be investigated, and the boundary impact as well. |