Numerical investigation of parametric resonance due to hydrodynamic coupling in a realistic wave energy converter

Abstract

Representative models of the nonlinear behavior of floating platforms are essential for their successful design, especially in the emerging field of wave energy conversion where nonlinear dynamics can have substantially detrimental effects on the converter efficiency. The spar buoy, commonly used for deepwater drilling, oil and natural gas extraction and storage, as well as offshore wind and wave energy generation, is known to be prone to experience parametric resonance. In the vast majority of cases, parametric resonance is studied by means of simplified analytical models, considering only two degrees of freedom (DoFs) of archetypical geometries, while neglecting collateral complexity of ancillary systems. On the contrary, this paper implements a representative 7-DoF nonlinear hydrodynamic model of the full complexity of a realistic spar buoy wave energy converter, which is used to verify the likelihood of parametric instability, quantify the severity of the parametrically excited

Modelling of Parametric Resonance for Heaving Buoys with Position-Varying Waterplane Area

“…An NLFK model, therefore, incorporates both nonlinear excitation and restoring forces, whereby the hydrodynamic parameters vary at each time step, being recalculated for the exact wetted body surface at that instant. This modelling approach has been utilised to successfully capture the parametric pitch/roll motion in heaving point absorber WECs, such as the Wavebob [32,37,40,81,82], the CorPower WEC [83] and the Oscillating Water Column Spar Buoy [84][85][86][87]. A comparison of a NLFK against a CFD simulation for capturing parametric resonance in a heaving point absorber is performed in [88], reporting that the NLFK model is more than 5000 times faster than the CFD simulation with comparable accuracy.…”

Nonlinear Dynamic and Kinematic Model of a Spar-Buoy: Parametric Resonance and Yaw Numerical Instability

“…Furthermore, Figure 3 shows that, due to nonlinear kinematic coupling, as the wave height increases there is additional energy transferred from RAO(4) and RAO(5) to RAO (6). For further detailed discussion of the nonlinear dynamics of parametric resonance, please refer to the work in [35,46].…”

Compact floating wave energy converters arrays: Mooring loads and survivability through scale physical modelling

“…Natural pitch and roll periods are expected to have very similar natural period values due to the device axisymmetric geometry. The natural pitch period presented a value of 35.2 s, about 3.5 times larger than the natural heave period, and therefore avoiding the condition that promotes parametric resonance in roll and pitch, which induces a dynamic instability [54]. Parametric resonance tends to be triggered when the natural pitch/roll period value is twice the incoming wave period, being more severe for large heave amplitudes.…”