This paper aims at comparing different implementations of the Morison equation for seakeeping analysis in frequency domain. For more consistency, different wave models are considered and the total wave field (incoming wave, the diffracted and the radiated wave field) is included in the Morison equation. A state-of-the-art of theMorison equation and the drag force linearized forms are presented. The implementation procedure, based on an iterative frequency domain scheme, is developed for the regular and the irregular wave cases. Seakeeping analysis of an offshore wind turbine is considered as an application case. A comparison between numerical simulations and measured responses is presented. For the floater’s numerical model, skirts damping effect and hydrodynamic loads applied on cylindrical bracings are modeled using the Morison equation. The drag and inertia coefficients are considered constant for all sea states and calibrated using the experimental results. Response amplitude operators (RAOs) and short-termstatistics of motions show a good agreement between experimental and numerical results. The influence of different calculation parameters including the wave model (regular/irregular) and the wave fields (incident/total) are investigated.

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Wave diffraction-radiation by a porous body is investigated here. Linear potential flow theory is used and the associated Boundary Value Problem (BVP) is formulated in frequency domain within a linear porosity condition. First, a semi-analytical solution for a truncated porous circular cylinder is developed using the dedicated eigenfunction expansion method. Then the general case of wave diffraction-radiation by a porous body with an arbitrary shape is discussed and solved through Boundary Integral Equation Method (BIEM). The main goal of these developments is to adapt the existing diffraction-radiation code (HYDROSTAR) for that type of applications. Thus the present study of the porous cylinder consists a validation work of (BIEM) numerical implementation. Excellent agreement between analytical and numerical results is observed. Porosity influence on wave exciting forces, added mass and damping is also investigated.

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