Impact of some design considerations on the wake recovery of vertical-axis turbines

Abstract

Using delayed detached-eddy simulations, the objective of this paper is to show the effects of some design parameters on the wake recovery of vertical-axis turbines. To that end, the wake dynamics of a single-blade turbine is analyzed and compared for two different positions of blade attachment point and for two designs of blade support structures (struts). The results show that the chordwise position of the blade attachment point affects the temporal evolution of the blade circulation during the turbine revolution. More precisely, we demonstrate that an attachment point positioned near the trailing edge of the blade leads to a temporal vorticity distribution that is detrimental to the wake recovery. Moreover, we show that the use of tip struts, that are highly beneficial to the turbine efficiency, affects the spatial distribution of the vortex structures shed by the turbine as well as the wake recovery. The results presented in this paper suggest that the velocity recovery in the wake is highly dependent on the very near-wake vortex dynamics. Therefore, we can infer that any geometric parameter affecting the temporal and spatial distributions of the vorticity shed by the blades can significantly alter the wake recovery of vertical-axis turbines.