Velocity vector and turbulence in the symmetry plane of a Darrieus wind generator

Abstract

This paper reports experimental results for the flow field of a Darrieus type wind generator model of diameter 1.7 m tested in a closed circuit wind tunnel. Velocity vector and turbulence measurements in the symmetry plane of the rotor (horizontal plane) were taken using an X-hotwire. The measurements covered the near field around the model from half a rotor diameter upstream to one diameter downstream. The results indicated that the edges of the wake are easily identifiable by the abrupt change in the wake velocity to that of the undisturbed flow and also by the high turbulence level. At tip speed ratios of up to about 5.4, the upstream flow, even at a location within half a rotor diameter, seems not to be affected by the operation of the wind generator, whilst small effects are present at a tip speed ratio of 7. The flow field downstream of the rotor is asymmetric with a tendency for the flow to turn in the direction of rotor rotation by only 7° at a tip speed ratio of around 4.