Numéro : 2042 - Year : 1987
Determination of the dynamic behaviour of rudders fluid/structure interaction
T. T .CHAU, Ingénieur, Institut de Recherches de la Construction Navale ( IRCN)
L.BROSSET, Ingénieurs, Institut de Recherches de la Construction Navale ( IRCN)
The downstream flow of the propeller induces unsteady pressures on rudders. At natural frequencies, dynamic resulting loads increase fatigue effects drastically and may lead to rupture.
This paper investigates different methods for the prediction of eigenfrequencies and modes of such structures in air and water at different steps of the design.
Clearly, the main problem lies in the fluid effect around the rudder.
Two approaches are presented:
-The first one is a simple method of quick and cheap use to predict the first eigenfrequencies. The structure is discretized into beam elements with mechanical characteristics deduced from the structure. Added masses are evaluated from simple analytical formulas.
-The second one consists in solving the hydroelastic problem by a 3D model of the structure coupled with a fluid discretisation involving finite and infinite incompressible elements.
These two methods are compared in the case of a rudder and conclusions are drawn with respect to their application domain.