Re-creation of site-specific multi-directional waves with non-collinear current
© 2017 The Author(s). Published by Elsevier Ltd. Open Access funded by Engineering and Physical Sciences Research Council. Under a Creative Commons license: https://creativecommons.org/licenses/by/4.0/
Site-specific wave data can be used to improve the realism of tank test conditions and resulting outputs. If this data is recorded in the presence of a current, then the combined conditions must be re-created to ensure wave power, wavelength and steepness are correctly represented in a tank. In this paper we explore the impacts of currents on the wave field and demonstrate a simple, effective methodology for re-creating combined wave-current scenarios. Regular waves, a parametric unidirectional spectrum, and a complex site-specific directional sea state were re-created with current velocities representing 0.25, 0.5, and 1.0 m/s full scale. Waves were generated at a number of angles relative to the current, providing observations of both collinear and non-collinear wave-current interactions. Wave amplitudes transformed by the current were measured and corrected linearly, ensuring desired frequency and wavenumber spectra in the presence of current were obtained. This empirical method proved effective after a single iteration. Frequency spectra were within 3% of desired and wave heights normally within 1%. The generation-measurement-correction procedure presented enables effective re-creation of complex wave-current scenarios. This capability will increase the realism of tank testing, and help de-risk devices prior to deployment at sea.
The authors would like to thank the Energy Technologies Institute and RCUK Energy programme for funding this research as part of the IDCORE programme (EP/J500847/1), the UK EPSRC for funding the FloWave facility (EP/I02932X/1), and the European Marine Energy Centre for providing buoy data for the sea state replication work.
The final version is available from Elsevier via the DOI in this record.
Published online 28 October 2017