Projects per year
Abstract
the highest emphasis in semiempirical models. However it is an open
question whether inflow noise has a high emphasis. This illustrates the need
to investigate and improve the semiempirical model for noise due to
atmospheric turbulence. Three different aerodynamical models are
investigated in order to estimate the lift fluctuations due to unsteady
aerodynamics (Sears, W. R.: 1941, Some aspects of nonstationary airfoil
theory and its practical application; Goldstein, M. E. and Atassi, H. M.:
1976, A complete secondorder theory for the unsteady flow about an
airfoil due to a periodic gust; and Graham, J. M. R.: 1970, Lifting surface
theory for the problem of an arbitrarily yawed sinusoidal gust incident on a
thin aerofoil in incompressible flow). Two of these models are investigated
to find the unsteady lift distribution or pressure difference as function of
chordwise position on the aerofoil (Sears, W. R.: 1941; and Graham, J. M.
R.: 1970). An acoustic model is investigated using a model for the lift
distribution as input (Amiet, R. K.: 1975, Acoustic radiation from an airfoil
in a turbulent stream). The two models for lift distribution are used in the
acoustic model. One of the models for lift distribution is for completely
anisotropic turbulence and the other for perfectly isotropic turbulence, and
so is also the corresponding models for the lift fluctuations derived from
the models for lift distribution. The models for lift distribution and lift are
compared with pressure data which are obtained by microphones placed
flush with the surface of an aerofoil. The pressure data are from two
experiments in a wind tunnel, one experiment with a NACA0015 profile
and a second with a NACA63415 profile. The turbulence is measured by a
triple wired hotwire instrument in the experiment with a NACA0015
profile. Comparison of the aerodynamical models with data shows that the
models capture the general characteristics of the measurements, but the data
are hampered by background noise from the fan propellers in the wind
tunnel. The measurements are in between the completely anisotropic
turbulent model and the perfectly isotropic turbulent model. This indicates
that the models capture the aerodynamics well. Thus the measurements
suggest that the noise due to atmospheric turbulence can be described and
modeled by the two models for lift distribution. It was not possible to test
the acoustical model by the measurements presented in this work.
Original language  English 

Place of Publication  Roskilde 

Publisher  Risø National Laboratory for Sustainable Energy 
Number of pages  138 
ISBN (Print)  9788755037274 
Publication status  Published  Dec 2009 
Series  RisøPhD 

Number  47(EN) 
Keywords
 Wind energy
 Wind power meteorology
 RisøPhD47(EN)
 RisøPhD47
 RisøPhD0047
Fingerprint Dive into the research topics of 'Wind Turbines: Unsteady Aerodynamics and Inflow Noise'. Together they form a unique fingerprint.
Projects
 1 Finished

Noise from Wind Turbines due to Inflow Turbulence
Broe, B. R., Sørensen, J. N., Mann, J., Jacobsen, F., Graham, J. M. R. & Keith, G.
01/12/2004 → 27/01/2010
Project: PhD