  The proper orthogonal decomposition has been applied on a full-scale
horizontal-axis wind turbine to shed light on the wake characteristics behind
the wind turbine. In reality, the blade tip experiences high deflections even
at the rated conditions which definitely alter the wake flow field, and in the
case of a wind farm, may complicate the inlet conditions of the downstream wind
turbine. The turbine under consideration is the full-scale model of the
National Renewable Energy Laboratory 5MW onshore wind turbine which is
accompanied by several simulation complexities including turbulence, mesh
motion and fluid-structure interaction. Results indicated an almost similar
modal behaviour for the rigid and flexible turbines at the wake region. In
addition, more flow structures in terms of local vortices and fluctuating
velocity fields take place at the far wake region. The flow structures due to
the wake shed from the tower tend to move towards the center and merge with
that of the nacelle leading to an integral vortical structure 2.5 diameter away
from the rotor. Also, it is concluded that the exclusion of the tower leads to
missing a major part of the wake structures, especially at far-wake positions.
