Vortex models are basically potential flow models based on the calculation of the velocity
field about the turbine through the influence of vorticity in the wake of the blades. The
turbine blades are represented by bound or lifting-line vortices whose strengths are
determined using airfoil coefficient datasets and calculated relative flow velocity and angle of
attack. Larsen [7] first introduced the idea of the vortex model for a single blade element of a
VAWT. He used the vortex model for the performance prediction of a cyclogiro windmill.
The model is 2D, but if the vortex trailing from the rotor blade tips is considered, it may be