PIV data of straight blade and swept blade wind turbine

In large wind farms, the wake behind the upstream wind turbine affects the
performance of the downstream turbines which reduces the overall power
output. The geometry of the wind turbine blades has significant effects on
the mechanical efficiency of this process. Here, we suggest to utilize a
bio-inspired blade based on the common swift wing. Common swift is known
to be a long-distance flyer, able to stay aloft for long periods of time
by maintaining high lift and low drag. We study the near wake flow
characteristics of a horizontal turbine model with swept blades and its
aerodynamic loads. These are compared with a straight-bladed turbine. The
experiments were conducted in a water flume using particle image
velocimetry (PIV) technique. Both blades were studied for four different
speeds with freestream Reynolds numbers ranging from 23,000 to 41,000. Our
results show that the near wake developed behind the swept-back blade was
significantly different from the straight blade configuration. The near
wake developed behind the swept-back blade exhibited relatively lower
momentum loss and suppressed turbulent activity (mixing and production)
compared to the straight blade. Comparing the aerodynamic characteristics,
though the swept-back blade generated relatively less lift than the
straight blade, the drag was relatively lower as well. Thus, the
swept-back blade produced 2-3 times higher lift-to-drag ratio than the
straight blade. Based on the observations, we suggest that, with improved
design optimizations, using the swept-back configuration in wind turbine
blades can positively help to improve the energy loss in downstream wind
turbines in wind farms and can increase the overall energy efficiency.