Leishman_Reno02 - AIAA 2002-0037 Challenges in Modeling the...

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AIAA 2002-0037 Challenges in Modeling the Unsteady Aerodynamics of Wind Turbines J. Gordon Leishman Department of Aerospace Engineering, Glenn L. Martin Institute of Technology, University of Maryland at College Park, Maryland 20742. 21 st ASME Wind Energy Symposium and the 40 th AIAA Aerospace Sciences Meeting, Reno, NV For permission to copy or republish, contact the author or the American Institute of Aeronautics and Astronautics 1801 Alexander Bell Drive, Suite 500, Reston, VA 20191–4344
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Challenges in Modeling the Unsteady Aerodynamics of Wind Turbines J. Gordon Leishman Department of Aerospace Engineering, Glenn L. Martin Institute of Technology, University of Maryland at College Park, Maryland 20742. Abstract Many of the aerodynamic phenomena contributing to the observed effects on wind turbines are now known, but the details of the flow are still poorly understood and are challenging to predict accurately. Issues discussed herein include the modeling of the induced velocity field pro- duced by the vortical wake behind the turbine, the various unsteady aerodynamic issues associated with the blade sec- tions, and the intricacies of dynamic stall. Fundamental limits exist in the capabilities of all models, and misun- derstandings or ambiguities can also arise in how these models should be properly applied. A challenge for ana- lysts is to use complementary experimental measurements and modeling techniques to better understand the aerody- namic problems found on wind turbines, and to develop more rigorous models with wider ranges of application. Nomenclature a sonic velocity, ms 1 ¯ a pitch axis location, measured from mid-chord A rotor disk area, π R 2 , m 2 A i coefficients of indicial functions b i exponents of indicial functions c chord, m C Theodorsen function C l lift coefficient C m moment coefficient about 1/4-chord C l α lift curve slope, rad 1 C T rotor thrust coefficient, T / ( ρπΩ 2 R 4 ) h plunge displacement, m M free-stream Mach number N b number of blades q nondimensional pitch rate, = ˙ α c / V R rotor radius, m s distance in semi-chords, =( 2 / c ) R t 0 Vdt S Sears function (referenced to airfoil mid-chord) S 0 Sears function (referenced to airfoil leading-edge) Professor. Email: [email protected] Paper 2002-0037. Presented at the 21 st ASME Wind Energy Sym- posium and the 40 th AIAA Aerospace Sciences Meeting, Reno, NV, Jan. 14–17, 2002. Copyright c ° 2002 by J. G. Leishman. Pubished by the American Institute of Aeronautics and Astronautics, Inc. and the Institute of Mechanical Engineers, with permission. t time, s T rotor thrust, N U R velocity component parallel to blade, ms 1 U T velocity component perpendicular to blade, ms 1 v i average induced velocity, ms 1 V airfoil velocity, ms 1 V g gust convection velocity, ms 1 ~ V velocity vector at a Lagrangian marker, ms 1 V free-stream velocity, ms 1 ~ V ex external velocity field, ms 1 ~ V ind induced velocity, ms 1 w gust velocity induced normal to airfoil, ms 1 x , y , z Cartesian coordinates, m , m , m α angle of attack, rad α e
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This note was uploaded on 11/13/2011 for the course AEE 495 taught by Professor O.uzol during the Spring '11 term at Middle East Technical University.

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Leishman_Reno02 - AIAA 2002-0037 Challenges in Modeling the...

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