DOI 10.1016/j.renene.2023.05.125 While studies on horizontal axis tidal turbines are plentiful, those on ducted twin vertical axis alike HydroQuest’s turbines are lacking. For such a device, both the relative counter-rotation direction of the rotors and the tripod base geometry upstream are different between ebb and flood tide. Consequently, this paper analyses the effect of the two opposed flow directions on the hydrodynamic performance and on the wake of the turbine. The study is based on experimental measurements at a 1/20th scale in Ifremer’s wave and current flume tank. The hydrodynamic performance of the model are characterised over a wide range of operating points with the turbine installed on a tripod and on a monopile base. In addition, the 3D wake of the turbine is thoroughly analysed in the two flow directions using 3-component laser Doppler velocimetry. Overall, the drag and the maximum average power coefficient are not affected by the current direction but the optimal tip speed ratio is 7 % lower during ebb with 1.5 times higher power fluctuations compared to flood tide. Besides, the wake of the two rotor columns interact differently depending on the flow direction, leading to a 30 % faster surface averaged velocity recovery in the flood tide configuration. The observed effect of flow direction provides a better knowledge of twin vertical axis turbine wake interactions and highlights the impact of the gravity base geometry on the development of the overall turbine wake. This paper also provides a wide experimental database for the validation of numeric
Tidal energy, Cross-flow turbine, Experimental trials, Laser doppler velocimetry
| File | Pages | Size | Access | |
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Author's final draft | 28 | 5 Mo | ||
Fig. 23. Contours of the streamwise velocity at different altitudes in FC on the monopile base. The black crosses show the measurement point positions; the dashed, dash-dot and solid lines are ... | - | 1 Mo | ||
Fig. 24. Horizontal streamwise velocity profiles at different downstream distances at the centre of the turbine () in FC on the monopile base. | - | 216 Ko | ||
Fig. 25. Contours of the streamwise velocity in the plane at different positions along the width, in FC on the monopile base. The black crosses show the measurement point positions; the dashed,... | - | 544 Ko | ||
Fig. 26. Vertical streamwise velocity profiles at different downstream distances at the center of the turbine () in FC on the monopile base. | - | 224 Ko | ||
Fig. 27. Horizontal profiles of mean vertical velocity at different downstream distances and , in FC on the monopile base. | - | 205 Ko | ||
Fig. 28. Contours of the mean streamwise velocity in planes, viewed from downstream, with superimposition of arrow field of the mean transverse velocities in FC on the monopile base; the dashed, .... | - | 546 Ko | ||
Fig. 29. Contours of the turbulent kinetic energy computed on and viewed from downstream in FC on the monopile base. nb: the color scale is different in (a). | - | 783 Ko | ||
Publisher's official version | 16 | 8 Mo |
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