Wind Turbine Aerodynamics Part A: Basic Principles - Wind Turbine Technology: Fundamental Concepts of Wind Turbine Engineering - page 315

Figure 5-19. The wind velocity component U ¢ in the Glauert modification of the
momentum equation accounting for yaw heading error. [Glauert 1935a]
output of a 3-m, two-bladed HAWT in a wind tunnel at various angles of yaw. The results
are shown in Figure 5-20, in the form of ratios of power with yaw error to power without
yaw error. Tests were run at three different tip-speed ratios. For comparison, power reduc-
tions predicted in accordance with strip theory are also shown in the figure. Generally, strip
theory predicts too large a loss in power from yaw error. Performance was found to vary as
Figure 5-20. Measured and calculated effects of yaw error on the power output of a
3-m HAWT. Test data from [Anderson et al. 1982]