EAWE PhD-Seminar, Ris

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EAWE PhD-Seminar, Risø 4. October

• PhD-Student
• Brian Riget Broe
• Semi-Empirical modeling of Aerodynamical Noise
• Risø National Laboratory
• Frederiksborgvej 399
• 4000 Roskilde, Denmark
• Aeroacoustics
• and
• Fluctuating Lift

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Sources of aerodynamic noise
From Moriarty (2003)
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Modeling the inflow noise
Model by Amiet (1975)
The power spectrum of the surface pressure
Task Find the Fluctuating lift for an
arbitrary profile
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2-D gust on a flat plate
Sears (1941) and Graham (1971)
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2-D gust on a flat plate, Results
Sears (1941) 1-D
A sinusoidal gust impinging on a semi-infinite
flat plate. k is the wave vector which is in the
plane of the flat plate. The wave vector has the
component ? in the x-direction and ? in the
y-direction. The wave front hits the edge of the
plate in an angle. For the 1-D case ? is zero.
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Measured surface pressure (1)
Measurements by Mish et al. (2006) for a NACA
0015 profile
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Measured surface pressure (2)
Measurements by Mish et al. (2006) for a NACA
0015 profile
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2-D gust on a profile
A sinusoidal gust impinging on a Joukowsky
aerofoil. k is the wave vector. The wave vector
has the component ? in the x-direction and ? in
the z-direction. For the 1-D case ? is zero.
Goldstein and Atassi (1976)
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Joint lift response of angle attack and camber
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Lift response due to thickness
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Summary

• A function for the fluctuating lift needs to be
  found for an arbitrary profile
• Measurements of the surface pressure is going to
  be made by Risø for a Risø profile
• Work on model by linearized theory to find the
  fluctuating lift due thickness

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References

• Listed in order of appearence
• P. Moriarty and P. Migliore, Semi-Empirical
  Aeroacoustic Noise Prediction Code for Wind
  Tubines, 2003, NREL/TP-500-34478.
• R. K. Amiet, Acoustic Radiation From An Airfoil
  In A Turbulent Stream, 1975, J. Sound and Vibr.,
  41(4), 407-420.
• P. F. Mish and W. J. Devenport, An experimental
  investigation of unsteady surface pressure on an
  airfoil in turbulence-Part 1 Effects of mean
  loading, 2006a, J. Sound and Vibr., 296, 417-446.
• W. R. Sears, Some Aspects of Non-Stationary
  Airfoil Theory and Its Practical Application,
  1941, J. of the Aeronatical Sc., Vol. 8, No. 3,
  104-108.
• J. M. R. Graham, Lifting Surface Theory for the
  Problem of an Arbitrarily Yawed Sinusoidal Gust
  Incident on a Thin Aerofoil in Imcompressible
  Flow, 1971, The Aeronautical Quart., 182-198.
• M. E. Goldstein and H. Atassi, A complete
  second-order theory for the unsteady flow about
  an airfoil due to a period gust, 1976, J. Fluid
  Mech., vol. 74, part 4, 741-765.
• H. M. Atassi, The Sears problem for a lifting
  airfoil revisited new results, J. Fluid Mech.,
  1984, vol. 141, 109-122.