Numerical analysis in a barge-type FOWT in aNySIM
Investigation on affection of moonpool’s damping lid factor in the system
E. Papadakis (TU Delft - Mechanical Engineering)
J.O. (Oriol) Colomes Gene – Mentor (TU Delft - Civil Engineering & Geosciences)
Alex van Deyzen – Mentor (Haskoning)
A. Grammatikopoulos – Graduation committee member (TU Delft - Mechanical Engineering)
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Abstract
This thesis investigates the hydrodynamic behavior of a barge-type Floating Offshore Wind Turbine (FOWT) equipped with a central moonpool, with particular focus on the influence of the damping lid method, a numerical approach used to approximate viscous damping in potential flow simulations. The damping lid factor ε was varied systematically to evaluate its impact on moonpool resonance, platform motions, and mooring system loads under both idealized and realistic sea states.
Hydrodynamic coefficients and motion response amplitude operators RAOs were first analyzed in the frequency domain using DIFFRAC, revealing strong sensitivity of the system to internal resonance modes when no damping is applied. The time domain simulations were then performed in aNySIM to assess the mooring tensions and the motion behavior under regular and irregular wave conditions. A minimum damping lid factor of ε = 0.035 was identified as sufficient to suppress unrealistic resonance amplification.
Finally, a case study for a North Sea scenario was carried out to compare the performance of the system between ε = 0.035 and ε = 0.1 in terms of serviceability and operational availability. Results showed that once the critical damping threshold is reached, the system response becomes relatively insensitive to further increases in ε.
The findings demonstrate that the damping lid is an effective and practical tool for modeling moonpool effects in barge-type FOWTs, and that a carefully selected damping factor for this specific barge type, can eliminate the need for more computationally intensive viscous simulations when evaluating global system behavior.