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Abstract
This research is devoted to the Large Eddy Simulation
(LES), and to lesser extent, wind tunnel measurements of
turbulent flows in wind energy. It starts with an
introduction to the LES technique associated with the
solution of the incompressible NavierStokes equations,
discretized using a finite volume method. The study is
followed by a detailed investigation of the SubGrid Scale
(SGS) modeling. New SGS models are implemented into
the computing code, and the effect of SGS models are
examined for different applications. Fully developed
boundary layer flows are investigated at low and high
Reynolds numbers, and thereafter, the fullydeveloped
infinite wind farm boundary later simulations are
performed. Sources of inaccuracy in the simulations are
investigated and it is found that high Reynolds number
flows are more sensitive to the choice of the SGS model
than their low Reynolds number counterparts. Wind tunnel
measurements of an airfoil at Reynolds numbers ranging
from 40,000 to 400,000 are carried out. The
measurements include detailed surface pressure as well
as force balance measurements for obtaining the lift, drag
and pressure distribution over the airfoil. Measurements
are performed in the upstroke and downstroke pitching
for angles of attack between −10◦ and +25◦ and the static
stall hysteresis phenomenon is investigated
experimentally. Following the wind tunnel
measurements, LES of the airfoil is performed using a
numerical wind tunnel for Re=40,000 and Re=100,000 at a
range of angles of attack. Laminarturbulent transition,
generation of laminar boundary layer separation, and
formation of stall cells are investigated. The simulated
airfoil characteristics are validated against measurements.
It is concluded that the LES computations and wind
tunnel measurements are in good agreement, should the
mesh resolution, numerical discretization scheme, time
averaging period, and domain size be chosen wisely.
A thorough investigation of the wind turbine wake
interactions is also conducted and the simulations are
validated against available experimental data from
external sources. The effect of several parameters on
the wake structures and blade loadings are
investigated. In particular, the role of SGS modeling on
the flow structures and wind turbine loadings is
quantified in great detail. It is found that, for the studied
cases (using bodyforce to represent wind turbines),
when a fine mesh is used to capture the tip vortices
somewhat accurately, the particular choice of the SGS
model is not a determining factor in simulation accuracy.
To increase the role of SGS models therefore, one needs
to coarsen the computational mesh, which, in return,
results in poor wake predictions.
Original language  English 

Publisher  DTU Wind Energy 

Number of pages  186 
ISBN (Electronic)  9788792896827 
Publication status  Published  2014 
Keywords
 Large Eddy Simulation
 Subgrid Scale modeling
 Atmospheric Boundary Layer
 Airfoil Aerodynamics
 Wind Turbine Wakes
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Dive into the research topics of 'Large Eddy Simulation of Turbulent Flows in Wind Energy'. Together they form a unique fingerprint.Projects
 1 Finished

Simulation and Modelling of Wakes and Wake Interaction in Offshore Wind Farms
Sarlak, H., Sørensen, J. N., Mikkelsen, R. F., Walther, J. H., Davidson, L., Olesen, N. A. & Shen, W. Z.
Technical University of Denmark
01/01/2011 → 25/08/2014
Project: PhD