1. Dialogue, equality and trust are keywords in our relations with our employees and all our collaboration partners www.risoe.dk 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

2. EAWE PhD-Seminar, Risø 4.-5. October, 2006 Sources of aerodynamic noise From Moriarty (2003)

3. 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

4. EAWE PhD-Seminar, Risø 4.-5. October, 2006 2-D gust on a flat plate Sears (1941) and Graham (1971)

5. 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

6. EAWE PhD-Seminar, Risø 4.-5. October, 2006 Measured surface pressure (1) Measurements by Mish et al. (2006) for a NACA 0015 profile

7. EAWE PhD-Seminar, Risø 4.-5. October, 2006 Measured surface pressure (2) Measurements by Mish et al. (2006) for a NACA 0015 profile

8. 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)

9. EAWE PhD-Seminar, Risø 4.-5. October, 2006 Joint lift response of angle attack and camber

10. EAWE PhD-Seminar, Risø 4.-5. October, 2006 Lift response due to thickness

11. 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

12. 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.