2.1.2. Design of rotor blade
Assuming that the rotor presents its possible maximum efficiency, the axial induction factor “a” from Betz theory is 1/3. Conversely, using the formula a = 1/3, each element of the blade can be designed. Therefore, the induction factors are induced following Eqs. (6) and (7) at optimal efficiency from element momentum theory by ignoring the drag term ( Burton et al., 2001 and Manwell et al., 2009). Furthermore, they include Prandtl’s loss factor because, as mentioned earlier, the blade tip loss causes changes in the axial and tangential induction factors, “a” and “aT”, at local sections.