The design of blades is still a major task for manufacturers. Aerodynamics and structures are intimately associated in this process, to account for fabrication cost, transportation/installation, maintenance and fatigue life. Steady flow modelization remains the primary preoccupation of the designers, while unsteady effects contribute to the overall system performance assessment.

The importance of unsteadiness and its modelization in wind turbine aerodynam­ics is greater than ever before, in large part due to the larger size of the blades and their greater “softness” or flexibility. Advanced designs are contemplated that incorporate blade sweep and winglets with a view to improving the performance and power cap­ture [18]. Composite materials allow for these increases in size and complexity, but also decreased stiffness. The question of fatigue has therefore become more relevant as the blades are subject to more vibrations, bending and twisting.

The vortex model has the potential of providing useful capabilities for the sim­ulation of aeroelastic phenomena. Some work has already been carried out in this direction [19]. More work needs to be done to obtain a realistic simulation tool that is cheap and reliable, and operates directly in the time domain, in contrast to the many approaches based on eigen-frequencies and eigen-modes in the frequency do­main with highly simplified aerodynamics. The hybrid method would be a natural candidate for the extension to fluid/structure interaction when viscous effects are important.