The present work considers an experimental investigation of wind turbine near wake by using Particle Image Velocimetry (PIV) visualization technique. The PIV technique gives a complete picture of all points at the domain under consideration. The study is focused on the effect of tip speed ratio () and Reynolds number (Rec) on the near wake characteristics. A three-blade model of wind turbine with airfoil SG 6040 16% is tested in water channel at Rec range between 1.28 ×104 and 7.68 ×104. Various tip speed ratios are tested between =2 and =12. Experiments are also performed at constant =8 and variable Rec in the range between 2.56 ×104 and 5.12 ×104.
The results show that as increases both wake width and length increase up to =9. For higher values of l, the wake width remains constant. The turbulence intensity measurements show that an increase of causes an increase of turbulence intensity in the wake. Experiments at constant tip speed ratio λ = 8 and variable Reynolds number showed smaller values of turbulence intensities, narrower and shorter wakes at lower values of Reynolds number. The tip vortices pitch showed its dependence on the number of blades (B) and tip speed ratio (). The pitch is weakly affected by Rec increase.
The wake rotation study showed significant effects on inflow angle () and power coefficient especially at low tip speed ratio. |
