Renewable Energy, 5th Edition

Figure 4.13 Reynolds number dependence of the lift-to-drag ratio, defined as the maximum value (as a function of the angle of attack) of the ratio between the lift and drag coefficients C_L and C_D. Based on Hütter (1977).

Assuming that C_D, C_L, and W are constant over the area A=∫c dz of the airfoil, the work done by a uniform (except in the vicinity of the airfoil) wind field u_in on a device (e.g., a ship) moving with a velocity U can be derived from (4.58) and (4.59),

$E=\mathit{F}·\mathit{U}.$

The angle β between u_in and U (see Fig. 4.14) may be maintained by ...