An experimental investigation was conducted to examine
the effects of incoming surface wind conditions on the
wake characteristics and dynamic wind loads acting on a
wind turbine model. The experimental study was performed
in a large-scale wind tunnel with a scaled Horizontal
Axial Wind Turbine (HA WT) model placed in two
different types of Atmospheric Boundary Layer (ABL)
winds with distinct mean and turbulence characteristics. In
addition to measuring dynamic wind loads acting on the
model turbine by using a force-moment sensor, a highresolution
Particle Image Velocimetry (PIV) system was
used to achieve detailed flow field measurements to characterize
the turbulent wake flows behind the model turbine.
The measurement results reveal clearly that, the discrepancies
in the incoming surface winds would affect the
wake characteristics and dynamic wind loads acting on the
model turbine dramatically. The dynamic wind loads acting
on the model turbine were found to fluctuate much
more significantly, thereby, much larger fatigue loads, for
the case with the wind turbine model sited in the incoming
ABL wind with higher turbulence intensity levels. The
turbulent kinetic energy (TKE) and Reynolds stress levels
in the wake behind the model turbine were also found to
be significantly higher for the high turbulence inflow case,
in comparison to those of the low turbulence inflow case.
The flow characteristics in the turbine wake were found to
be dominated by the formation, shedding and breakdown
of various unsteady wake vortices. In comparison with the
case with relatively low turbulence intensities in the incoming
ABL wind, much more turbulent and randomly
shedding, faster dissipation and earlier breakdown of the
wake vortices were observed for the high turbulence inflow
case, which would promote the vertical transport of
kinetic energy by entraining more high-speed airflow from
above to re-charge the wake flow and result in a much
faster recovery of the velocity deficits in the turbine wake.