Performance and midspan wake measurements on a H-Darrieus in controlled conditions

Performance and wake measurements on a H-Darrieus vertical axis wind turbine are discussed on the basis of an extensive experimental campaign performed at the large scale, high speed wind tunnel of the Politecnico di Milano (IT). The paper proposes a combined mechanical and fluid-dynamic investigation by virtue of an advanced measurement system that allows to reconstruct both phase-resolved thrust and torque acting on the machine and the phase-resolved multi-dimensional velocity field in the wake. The aerodynamic torque is presented as a function of the azimuthal angle of revolution, while the velocity field in the wake is fully characterized by means of a point to point detailed measurement on the midspan plane, where the influence of both blade support struts and tip vortices is negligible. Particular care is taken in the description of the experimental setup as well as in the presentation of the measurements. The here proposed achievements can be considered as a benchmark for the validation of several classes of computational tools.