Abstract: This paper presents a mean for reducing the torque
variation during the revolution of a vertical-axis wind turbine
(VAWT) by increasing the blade number. For this purpose, twodimensional
CDF analysis have been performed on a straight-bladed
Darreius-type rotor. After describing the computational model, a
complete campaign of simulations based on full RANS unsteady
calculations is proposed for a three, four and five-bladed rotor
architecture characterized by a NACA 0025 airfoil. For each
proposed rotor configuration, flow field characteristics are
investigated at several values of tip speed ratio, allowing a
quantification of the influence of blade number on flow geometric
features and dynamic quantities, such as rotor torque and power.
Finally, torque and power curves are compared for the analyzed
architectures, achieving a quantification of the effect of blade number
on overall rotor performance.
Abstract: A two-dimensional numerical simulation of the contribution
of both inertial and aerodynamic forces on the blade loads of
a Vertical-Axis Wind Turbine (VAWT) is presented. After describing
the computational model and the relative validation procedure, a
complete campaign of simulations - based on full RANS unsteady
calculations - is proposed for a three-bladed rotor architecture characterized
by a NACA 0021 airfoil. For each analyzed angular velocity,
the combined effect of pressure and viscous forces acting on every
rotor blade are compared to the corresponding centrifugal forces,
due to the revolution of the turbine, thus achieving a preliminary
estimation of the correlation between overall rotor efficiency and
structural blade loads.