Experimental Investigation of Surface Waves Effect on a Ducted Twin Vertical Axis Tidal Turbine

Type Article
Date 2023-10
Language English
Author(s) Moreau Martin1, Germain GregoryORCID1, Maurice Guillaume2
Affiliation(s) 1 : Ifremer, Marine Hydrodynamics Laboratory, LHyMar, 150 Quai Gambetta, 62200 Boulogne-sur-Mer, France
2 : HydroQuest SAS, 16 Chemin de Malacher, 38240 Meylan, France
Source Journal Of Marine Science And Engineering (2077-1312) (MDPI AG), 2023-10 , Vol. 11 , N. 10 , P. 1895 (18p.)
DOI 10.3390/jmse11101895
Note This article belongs to the Special Issue Tidal and Wave Energy
Keyword(s) tidal energy, cross-flow turbine, tank tests, surface waves

The cost effective design of tidal turbines requires a good estimation of the loading cycles and their extrema that are related to the unsteady fluctuations of the current velocity. Apart from the ambient turbulence, the main source of velocity fluctuations is the presence of surface waves. In the present study, we analyse the effect of waves propagating against the current on the performance and the loads of a twin vertical axis tidal turbine by an experimental approach at a 1/20 scale. Overall, the results show little or no effect of the waves on the average power and loads compared to the condition with current only, but a significant impact on their standard deviation that rises linearly with the waves amplitude. The drag, lift and pitching moment show extended ranges up to 7.5 times higher and extreme values exceedance by 60 to 100 % with irregular waves compared to the condition without waves. Those load and power fluctuation increase are fully due to the presence of waves as the coherence function between the rotor torque or the loads and the velocity spectra exceed 0.5 on the whole wave frequency bandwidth. The results also reveal a rotational sampling of the waves by the rotors that had also been observed on horizontal axis turbines. From a structural design point of view, the authors recommand to conduct tests in irregular wave conditions as the loads range and extreme values are 1.5 to 2 times higher than those encountered with regular waves of the same significant height and period.

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Preprint - 10.20944/preprints202308.2035.v1 20 1 MB Open access
Publisher's official version 18 1 MB Open access
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