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 (Re
c
) on the near wake characteristics. A threeblade
model

of wind turbine with airfoil SG 6040 16% is tested in water channel at Re
c
range
between 1.28 ×10
. Various tip speed ratios are tested between =2 and =12.
Experiments are also performed at constant =8 and variable Re
c
4
and 7.68 ×10
4

1
in the range between 2.56 ×10

and 5.12 ×10
4
.
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 Re
c
increase.
The wake rotation study showed significant effects on inflow angle () and power
coefficient especially at low tip speed ratio.