Wind tunnel study of the wake meandering downstream of a modelled wind turbine as an effect of large scale turbulent eddies

Experimental results on the unsteady behaviour of the wake of a modelled wind turbine in an atmospheric boundary layer (ABL) wind tunnel are presented. Tests were performed by modelling in the wind tunnel an ABL above a neutral moderately rough terrain at a geometric scale of 1:400, and a wind turbine with the help of the actuator disk concept. In order to characterise the meandering properties of its wake, velocity spectra and space–time correlations were measured through hot wire anemometry, both in the wake of the modelled wind turbine and in the wake of a solid disk. Comparing these two configurations allowed the examination of the differences between the random motion of the whole wind turbine wake characterising the meandering in the first case, and the periodic oscillations of the well-known vortex shedding, which appears behind a bluff-body, in the second case. Finally, the same experiments were performed in homogeneous and isotropic turbulent flows to exhibit the role of the large atmospheric turbulent scales in the meandering process.

► The unsteady behaviour of far-wakes downstream of porous and solid disks are studied.
► The porous disc models a wind turbine rotor (actuator disc concept).
► An atmospheric boundary layer is modelled in a wind tunnel.
► The porous disc wake meandering is generated by the large turbulent eddies of the upstream flow.
► The wind turbine wake meandering could be due to the large atmospheric turbulent eddies of the upstream flow.