**2.2 Unsteady aerodynamic**

Before starting the design optimization process, steady and unsteady aerodynamic analyses should be conducted. These analyses can be accomplished either using the blade element momentum (BEM) or by applying computational fluid dynamics (CFD). A detailed comparison between the two methods can be found in [6]. The two methods are used to solve the blade mathematical model, which is usually has a form of differential equation. The mathematical model should provide the relation between the different variables and parameters of a typical wind turbine blade. One of the most popular and widely used mathematical models in wind turbine analysis and design is the blade element momentum (BEM) method. A general procedure for applying the BEM method can be summarized as follows [1]:


More details about the BEM method can be found in [6].
