Second-order hydrodynamics induce loads and motions at the sum- and difference-frequencies of the incident waves. These effects have often been ignored in offshore wind analysis, under the assumption that they are significantly smaller than first-order effects. The sum- and difference-frequency loads can, however, excite eigenfrequencies of the system, leading to large oscillations that strain the mooring system or vibrations that cause fatigue damage to the structure.
Bayati, I.; Jonkman, J.; Robertson, A.; Platt, A.
National Renewable Energy Laboratory
Design Methods, Tools & Standards
Controls & Reliability
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