Propeller excitation forces
The propeller is a potential source of noise and vibrations in a ship. The vibration of a propeller are strongly related to the variation in inflow velocity (wake-field), the clearance from propeller tip to hull surface and blade geometry. The hull form should be optimised to make the wake-field as uniform as possible. Sufficient clearance to the hull must be provided. Adding skewback to the propeller gives less load variation and cavitation on the propeller blades. For given conditions the pressure pulses can be minimised using tip off-loading (reduced pitch at the tip) and skew.