Abstract:

One of the consequences of the up-scaling of wind turbines is that the aerodynamic loading over the rotor isk has become more non-uniform caused by wind shear and the rotational sampling of the turbulence. The question is how well we model this effect in our aeroelastic codes based on the BEM theory. In HAWC2 this is taken into account as the BEM model is implemented in the grid points of a fixed grid covering the swept area. Modelling the impact of wake swirl and flow expansion is also commented on.

In order to improve the unsteady induction modelling close to the individual blades and in particular to improve the computation of aeroelastic damping a so-called near wake model has been developed. Originally the model has been developed by Beddoes for helicopter rotor applications. It is a simplified lifting line model for the individual blades taking into account only the first 90 deg. of the trailed vortices. The model will be shortly described and results from initial simulations with the near wake model in HAWC2 will be presented.

Recently, the HAWC2 code has been extended with the so-called Actuator Cylinder model for induction computations on VAWT´s. The model and the implementation are briefly described. A comparison with results from a number of other models is presented.