Abstract

An enhanced direct forcing immersed boundary method implemented in the open-source hydrodynamic framework REEF3D::CFD is used to simulate six-degrees-of-freedom (6DOF) motion response of a 1:30 scale point-absorber wave energy converter(WEC) under extreme wave conditions. The enhancement of the method is achieved with a new density interpolation method that removes unphysical spurious phenomena. The governing equations are solved on a staggered rectilinear grid. REEF3D::CFD uses the level set function to represent the free surface. A ray casting algorithm is employed to get inside-outside information in the vicinity of the body with the underlying Cartesian grid. The enhanced method is tested and validated based on the experimental data from the experimental wave tank campaign carried out in the Ocean and Coastal Engineering Laboratory, at Aalborg University, in Denmark. 

Abstract

In this paper, a simplified numerical approach is applied to the analysis of the linear vibrations of aluminum or composite marine propeller blades with embedded viscoelastic films, around a predeformed nonlinear state. This approach allows to evaluate in a sequential way the nonlinear deformation, induced by the generation of lift (propulsion phenomenon), and the acoustic power emitted (vibroacoustic phenomenon) of a non-cavitating flexible marine propeller blade. For a given incident flow, the deformation of an aluminum blade is much smaller than that of a composite blade. The composite blade’s deformation has a significant positive impact on lift generation whereas the deformation of the aluminum blade tends to reduce traction. The dynamic characteristics of the aluminum blade at rest and under the fluid induced static load are similar, while those of the composite blade are very different in these two cases. The simplified two-step approach proposed in this study is therefore useful to accurately assess the emitted sound power by the vibrating blades.