Fluid-structure interaction analysis of the rudder vibrations in propeller wake

Abstract

Severe vibrations on the rudder worsen the vibrations and noise of the vessel. This study examines the rudder vibrations induced by propeller wake considering the fluid-structure interaction. The propeller's turbulent wake is solved with large eddy simulation. The lock-in regime under the different rotational speeds of propeller is discussed. The results show that rudder suffers from span-wise bending under the load induced by the propeller wake. This span-wise bending strengthens when the rotational speed increases. The rudder's vibrations are excited at the excitation frequencies and the natural frequencies. The vibrations of the rudder are locked at the first natural frequency fn1 when the blade passage frequency (BPF) is lower than 1.83 fn1. The vibration mode is similar to the first natural vibration mode in this lock-in regime. Intense vibrations are observed at BPF when the BPF exceeds 1.83 fn1. The vibration at the first natural frequency strengthens again when the shaft frequency exceeds 0.715 fn1. The vibrations at high-order natural frequencies strengthen as the excitation frequencies increase. The vibration at secondary natural frequency fn2 strengthens when the BPF approaches 0.532 fn2.