This report contains results from the EFP-2007-II project "Program
for Research in Applied Aeroelasticity". The main results can be
summed up into the following bullets:
• 2D CFD was used to investigate tower shadow effects on both
upwind and downwind turbines, and was used to validate the
tower shadow models implemented in the aeroelastic code
• Using a streamlined tower reduces the tower shadow by 50%
compared to a cylindrical tower. Similar reductions can be
achieved using a four legged lattice tower.
• The application of laminar/turbulent transition in CFD
for airfoils is demonstrated. For attached flow over
thin airfoils (18%) 2D computations provide good results
while a combination of Detached Eddy Simulation and laminar/
turbulent transition modeling improve the results in stalled
conditions for a thick airfoil.
• The unsteady flow in the nacelle region of a wind turbine is
dominated by large flow gradients caused by unsteady shedding
of vortices from the root sections of the blades.
• The averaged nacelle wind speed compares well to the
freestream wind speed, whereas the nacelle flow angle is highly
sensitive to vertical positioning and tilt in the inflow.
• The trailing edge noise model, TNO, was implemented and
The results showed that the noise was not predicted accurately,
but the model captured the trends and can be used in
airfoil design. The model was implemented in the airfoil design
tool AIRFOILOPT and existing airfoils can be adjusted
to maintain the aerodynamic characteristics, but with reduced
noise in the order of up to 3dB in total sound power level and
up to 1dB with A-weighting.
• 2D CFD simulations are performed to verify their capability
in predicting multi element airfoil configurations. The present
computations show good agreement with measured performance
from wind tunnel experiments.
• The stochastic fluctuations of the aerodynamic forces on blades
in deep-stall have an insignificant effect on the risk of stallinduced
vibrations predicted by quasi-steady aerodynamic
models, but more realistic models of deep-stall aerodynamics
must be developed to finally conclude on the real risk of
stallinduced vibrations at standstill.
• Finite element analysis shows that local blade cross section
caused by global blade deflection do not have significant
influence on the aerodynamic performance.
|Series||Denmark. Forskningscenter Risoe. Risoe-R|
- Wind energy
- Aeroelastic Design