Longitudinal vibration and unsteady thrust transmission of the rim driven thruster induced by ingested turbulence

Abstract

The longitudinal vibration characteristics of the rim driven thruster (RDT) induced by the ingested turbulence are numerically studied and compared with that of the traditional shaft driven propeller (SDP). The pressure spectrum acted on the blade surface is first computed using the correlation method based on strip theory and the statistical characteristics of isotropic turbulence. Appling the computed pressure spectrum as excitation, the random vibration response of the whole immersed thruster is obtained using the mode superposition method. The differences between the vibration responses, especially the longitudinal unsteady thrust transmission characteristics, of the two kinds of propulsors that have the same blade geometry are discussed. Computational results show that though RDT has lower hydrodynamic damping in the lower order bending modes, its resonant amplification on the unsteady thrust is still lower that of SDP for the lower modal force induced by the poor coincidence between the modal shape and space distribution of excitation. A potential merit of traditional SDP is that it has better attenuation effect on the unsteady thrust in the frequency band between the first and second bending modes of the propeller blade.