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Numerical study of the flow field around hydrokinetic turbines with winglets on the blades

Design methods and concepts that can increase the energy conversion efficiency of marine and river current turbines are of great importance for the development and wider utilization of this emerging renewable energy technology. This work is aimed to improve hydrodynamic performances of the hydrokinetic turbines to get as close as possible to the theoretical energy conversion efficiency limitation of 59.3%, known as the Lanchester–Betz– Joukowsky limit. The winglets are integrated at the turbine blade tips to reduce the effect of the tip vortex. The winglet design concept is adopted from the jet aircraft and adjusted to the hydrokinetic turbine application. The numerical investigation of the winglets impact on the hydrodynamic performances was performed using computational fluid dynamic (CFD). The results indicate that winglets subdue the strength of tip vortices, which is reflected through the increase in the power extracted. It has been confirmed that winglet height has a great influence on the power coefficient increase, which for higher winglets reaches the value above 50%. The analysis of the wake regions behind turbines pointed out that the turbines with winglets form stronger vortices in the far wake zone which may influence the back- flow turbine installed in row array.

Marine current turbine ; Hydrokinetic turbines ; Design improvements ; Winglets ; Blade tip losses reduction ; Wake recovery zone

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