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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

EAWE PhD-Seminar, Risø 4.-5. October, 2006

Sources of aerodynamic noise

From Moriarty (2003)

EAWE PhD-Seminar, Risø 4.-5. October, 2006

Modeling the inflow noise

Model by Amiet (1975)

The power spectrum of the surface pressure

Task: Find the Fluctuating lift for an arbitrary profile

EAWE PhD-Seminar, Risø 4.-5. October, 2006

2-D gust on a flat plate

Sears (1941) and Graham (1971)

EAWE PhD-Seminar, Risø 4.-5. October, 2006

2-D gust on a flat plate, Results

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.

Sears (1941) 1-D

EAWE PhD-Seminar, Risø 4.-5. October, 2006

Measured surface pressure (1)

Measurements by Mish et al. (2006) for a NACA 0015 profile

EAWE PhD-Seminar, Risø 4.-5. October, 2006

Measured surface pressure (2)

Measurements by Mish et al. (2006) for a NACA 0015 profile

EAWE PhD-Seminar, Risø 4.-5. October, 2006

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)

EAWE PhD-Seminar, Risø 4.-5. October, 2006

Joint lift response of angle attack and camber

EAWE PhD-Seminar, Risø 4.-5. October, 2006

Lift response due to thickness

EAWE PhD-Seminar, Risø 4.-5. October, 2006

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

EAWE PhD-Seminar, Risø 4.-5. October, 2006

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.