@ARTICLE{Strzelczyk_Piotr_The_2006,
 author={Strzelczyk, Piotr},
 volume={vol. 53},
 number={No 3},
 journal={Archive of Mechanical Engineering},
 pages={279-298},
 howpublished={online},
 year={2006},
 publisher={Polish Academy of Sciences, Committee on Machine Building},
 abstract={In the paper, the author presents a certain method of calculation of Horizontal Axis Wind Turbine (HAWT) performance for yawed flow conditions. The presented model is developed on the basis of propeller theory described in [23). Te model employs the results of the vortex theory of propeller combined with momentum and angular momentum theorems for the HAWT wake. In the model, the blade element is regarded as a source of tangential and axial force acting on air at actuator disk surface. The momentum equations are corrected for the effect of finite number of blades by introduction of Prandtl tip-loss factor to the equations. Thanks to the approximation of lift force coefficient vs. angle of attack by sine curve, one may get a quadratic equation for local axial velocity component. Tangential component of induced velocity may be calculated from relations obtained from vortex theory of HAWT. This allows us to avoid an iterative solution for induced velocity, unlike in most of the HAWT and propeller theories. The blade section drag is incorporated to calculations of total drag of rotor and power, when induced velocity components are known, and hence blade element angle of attack is determined. To incorporate the effect of blade element stall-delay due to blade rotation, a simple semi-empirical model proposed by Tangier and Selig has been applied. The calculations are compared with experimental data obtained at Riso 100 kW experimental turbine test site and at the Grumman Wind Stream 33 turbine modified by NREL. The comparison includes power output as well as blade element angles of attack. The presented results show that the method described in the paper underestimates performance for low speed winds, whereas for strong winds the power output is slightly overestimated. For average angles of attack, one may see that for small tip speed ratios angles of attack are overestimated. At high tip speed ratios, however, angles of attack are underestimated. It was shown that there is a need to take into account the work done by side force on the tangential inflow component to obtain correct power curves for yawed flow conditions.},
 type={Article},
 title={The method of calculation of horizontal axis wind turbine performance at yawed flow conditions by the use of simplified vortex method},
 URL={http://www.journals.pan.pl/Content/124918/PDF/7_MECHANICAL_53_2006_3_Strzelczyk_The_Method.pdf},
 keywords={wind turbine, wind turbine aerodynamics},
}