Improved transient water wave technique for the experimental estimation of ship responses

Reilhac, P. Roux de; Bonnefoy, Félicien; Rousset, Jean-Marc; Ferrant, P.

doi:10.1016/j.jfluidstructs.2011.01.002

Cited by 10 publications

(4 citation statements)

References 13 publications

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“…This phase-based harmonic separation method relies on a Stokes-like structure of the studied wave-driven response. It has been used to analyse various nonlinear wave phenomena involving fixed (Fitzgerald et al 2014;Zhao et al 2017;Chen et al 2018) and floating (Roux de Reilhac et al 2011;Chen et al 2021) offshore structures, as well as higher-order responses in coastal problems (Orszaghova et al 2014;Whittaker et al 2017;Judge et al 2019). The above studies utilise short deterministic wave groups.…”

Section: Identifying Nonlinear Resonant Responsesmentioning

confidence: 99%

Wave- and drag-driven subharmonic responses of a floating wind turbine

et al. 2021

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The nonlinear hydrodynamic responses of a novel spar-type soft-moored floating offshore wind turbine are investigated via analysis of motion measurements from a wave-basin campaign. A prototype of the TetraSpar floater, supporting a $1:60$ scale model of the DTU 10 MW reference wind turbine, was subjected to irregular wave forcing (with no wind) and shown to exhibit subharmonic resonant motions, which greatly exceeded the wave-frequency motions. These slow-drift responses are excited nonlinearly, since the rigid-body natural frequencies of the system lie below the incident-wave frequency range. Pitch motion is examined in detail, allowing for identification of different hydrodynamic forcing mechanisms. The resonant response is found to contain odd-harmonic components, in addition to the even harmonics expected a priori and excited by second-order difference-frequency hydrodynamic interactions. Data analysis utilising harmonic separation and signal conditioning suggests that Morison drag excitation or third-order subharmonic potential flow forcing could be at play. In the extreme survival-conditions sea state, the odd resonant responses are identified to be drag-driven. Their importance for the tested floater is appreciable, as their magnitude is comparable to the second-order potential flow effects. Under such severe conditions, the turbine would not be operating, and as such neglecting aerodynamic forcing and motion damping is likely to be reasonable. Additionally, other possible drivers of the resonant pitch response are explored. Both Mathieu-type parametric excitation and wavemaker-driven second-order error waves are found to have negligible influence. However, we note slight contamination of the measurements arising from wave-basin sloshing.

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Section: Identifying Nonlinear Resonant Responsesmentioning

confidence: 99%

Wave- and drag-driven subharmonic responses of a floating wind turbine

et al. 2021

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“…These waves contain broad band frequency content that allow the response as a function of frequency to be obtained from a single test using a DFT analysis. Similar to Roux de Reilhac et al (2011), a modified periodogram technique (Welch's method) was applied to extract RAOs as smooth curves.…”

Section: Response Amplitude Operatorsmentioning

confidence: 99%

Experimental and numerical comparisons of self-reacting point absorber wave energy converters in regular waves

et al. 2015

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“…The parameters defining the first control signal the focal point is located at x f frequency bandwidth is ∆f = 0.33 Hz, the central frequency π. The wave packet is built with a constant steepness spectrum, this avoids premature wave breaking as all the components within the wave packet maintain the same scale respect to wave steepness, Reilhac et al, (2011). The experimental layout used for the tests is shown in Fig.…”

Section: Focused Wave In Constant Water Depthmentioning

confidence: 99%

Focused Wave Generation in Laboratory Flumes Over Uneven Bottom

Fernández

Sriram²,

Schimmels

et al. 2014

Int. Conf. Coastal. Eng.

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A proper design of offshore and coastal structures requires further knowledge about extreme wave events. Such waves are highly nonlinear and may occur unexpectedly due to diverse reasons. One of these reasons is wave-wave interaction and the wave focusing technique represents one option to generate extreme wave events in the laboratory. The underlying mechanism is the superimposition and phasing of wave components at a predefined location. To date, most of the existing methods to propagate target wave profile backwards to the position of the wave generator apply linear wave theory. The problem is that the generated waves with different frequencies generate new components which do not satisfy the linear dispersion relation. As a result, small changes in the wave board control signal generally induce large and random shifts in the resulting focused wave. This means that iterations are necessary to get the required wave profile at the correct position in the flume. In this study, a Self Correcting Method (SCM) is applied to optimize the control signal of the wave maker in a Numerical Wave Tank (NWT). The nonlinearities are included in the control signal and accurate wave focusing is obtained irrespective of the prevailing seabed topography (horizontal or sloping) and type of structure (reflective or absorbing). The performance of the proposed SCM is numerically investigated for a wide variety of scenarios and validated by scale model tests in the Large Wave Flume (Großer Wellen Kanal, GWK), Hannover, Germany. The strengths and limitations of the proposed SCM are discussed, including the potential for further developments.

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Improved transient water wave technique for the experimental estimation of ship responses

Cited by 10 publications

References 13 publications

Wave- and drag-driven subharmonic responses of a floating wind turbine

Wave- and drag-driven subharmonic responses of a floating wind turbine

Experimental and numerical comparisons of self-reacting point absorber wave energy converters in regular waves

Focused Wave Generation in Laboratory Flumes Over Uneven Bottom

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