Dialogue, equality and trust are keywords in our relations with our employees and all our collaboration partners EAWE PhD-Seminar, Risø 4. October PhD-Student Brian Riget Broe Semi-Empirical modeling of Aerodynamical Noise Risø National Laboratory Frederiksborgvej Roskilde, Denmark Aeroacoustics and Fluctuating Lift

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

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

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

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

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

EAWE PhD-Seminar, Risø October, 2006 Lift response due to thickness

EAWE PhD-Seminar, Risø 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 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 R. K. Amiet, Acoustic Radiation From An Airfoil In A Turbulent Stream, 1975, J. Sound and Vibr., 41(4), 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, W. R. Sears, Some Aspects of Non-Stationary Airfoil Theory and Its Practical Application, 1941, J. of the Aeronatical Sc., Vol. 8, No. 3, 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., 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, H. M. Atassi, The Sears problem for a lifting airfoil revisited – new results, J. Fluid Mech., 1984, vol. 141,