Development of near wake of a HAWT depending on hub height

Abstract

This paper studies the wake of horizontal axis wind turbine. Flow exploration is conducted in wind tunnel, where the turbine is placed in vicinity of the tunnel wall. The objective is to investigate the wake and its interaction with the wall. The influence of the wall on the wake characteristics is studied for ratios “hub height/rotor diameter” h/D of 0.7, 1.0 and 2.25. The boundary layer on the wind tunnel wall permits to study the rotor blades operating inside and outside this boundary layer. The measurements of velocity field behind the rotor are obtained by means of particle image velocimetry. The analysis of results shows that the vortex tubes close to the wall, i.e. in the lower part of the wake, have lower intensity in comparison with the same vortex tubes in the upper part. The averaged velocity profiles of the wake, expressed in a coordinate system with the origin located at the rotor axis, show the influence of hub height on velocity distribution in the wake.