Since the last decade the world energy supply is shifting from fossil- to renewable energy resources. Wind energy is one of the main resources of this new type of energy. However, a lot of work still needs to be done on the e_ciency improvements. This mainly results in increased rotor diameters. These large wind turbines are highly subjected to the vagaries of the atmosphere. Therefore a lot of research is being performed to the inuence of atmospheric conditions on the aerodynamic and structural behavior of wind turbines. Typical atmospheric conditions that are relevant for wind turbine design are gusts, vertical velocity shear, direction change and turbulence. The highly unsteady character of these atmospheric conditions make most of available empirical models inadequate for predicting the ow behavior around wind turbine parts. CFD can be a good alternative. However, wind engineering is a relatively new part in CFD and a lot of investigations still need to be done.