1. Introduction and background
The use of BE-M (Blade Element e Momentum) models for the
design and analysis of vertical-axis wind turbines has aroused
a large credit, not only in research and academic communities but
also in industrial appliances, thanks to general acceptable accuracy
of the results, as well as widely available literature and code
simplicity. BE-M theory, first introduced by Glauert [1] in order to
predict the structural dynamics and performance of airplane
propellers, was adjusted for vertical-axis wind turbine aerodynamics
by Templin [2], obtaining the most elementary approach
based on momentum theory, named single-streamtube model.
Strickland [3] extended Templin’s approach by considering the
single streamtube as composed of a number of adjacent and
aerodynamically independent smaller streamtubes, thus allowing
the use of airfoil characteristics based on local (rather than on
average) Reynolds number. This approach, named multiplestreamtube
model, was further developed by several authors
[4e9] by placing two actuator discs behind each other, thus
combining the multiple streamtube model prediction tool with the
Computational Fluid Dynamics (CFD) can nowadays be considered
as a powerful design tool, whose integration into industrial
development and production life-cycles is continuously rising. As
observed by Caridi [2], this was made possible because of two main
factors: