Hybrid CFD-source terms modelling of a diffuser-augmented vertical axis wind turbine

In order to reduce the calculation time in the analysis of a diffuser augmented H-Darrieus wind turbine (DAWT), a hybrid CFD-source terms 2D approach, relying on a new experimental-based dynamic stall model, was adopted. This method consists in solving the blades load by means of an analytic model, whereas the overall flow field is calculated through a simplified CFD. The new model was compared with a complete CFD exhibiting a satisfying agreement both for the case of a bare turbine and an unoptimized DAWT. By virtue of the rapidity of the new model, an optimization analysis of the diffuser design was carried out. A great power gain was achieved, thanks to unexpected aerodynamic phenomena, but an even greater increase of the frontal area was necessary. The critical issues of the modelling approach and the proposed DAWT are discussed.