Abstract
AbstractIn this study, the performance, drag, and horizontal midplane wake characteristics of a vertical‐axis Savonius wind turbine are investigated experimentally. The turbine is drag driven and has a helical configuration, with the top rotated 180° relative to the bottom. Both performance and wake measurements were conducted in four different inflow conditions, using Reynolds numbers of ReD≈1.6×105 and ReD≈2.7×105 and turbulence intensities of 0.6% and 5.7%. The efficiency of the turbine was found to be highly dependent on the Reynolds number of the incoming flow. In the high Reynolds number flow case, the efficiency was shown to be considerably higher, compared with the lower Reynolds number case. Increasing the incoming turbulence intensity was found to mitigate the Reynolds number effects. The drag of the turbine was shown to be independent of the turbine's rotational speed over the range tested, and it was slightly lower when the inflow turbulence was increased. The wake was captured for the described inflow conditions in both optimal and suboptimal operating conditions by varying the rotational speed of the turbine. The wake was found to be asymmetrical and deflected to the side where the blade moves opposite to the wind. The largest region of high turbulent kinetic energy was on the side where the blade is moving in the same direction as the wind. Based on the findings from the wake measurements, some recommendations on where to place supplementary turbines are made.
Highlights
The world's demand for renewable energy is rapidly increasing
The present study aims to improve our understanding of the wake and aerodynamic performance of a Savonius wind turbine with low and high levels of incoming turbulence intensity (TI)
This study has reported measurements of the aerodynamic performance and wake evolution of a Savonius wind turbine at two Reynolds numbers and two turbulence intensities
Summary
The world's demand for renewable energy is rapidly increasing. With the development of ‘‘greener’’ cities and the establishment of zeroand plus-energy buildings, this demand goes beyond large-scale electrical production systems such as offshore wind power and hydropower. There are few existing measurements that investigate the drag characteristics of a Savonius turbine in different Reynolds number and turbulent inflow conditions, resulting in a gap in the literature Another important aspect in the urban application of vertical wind turbines is the development of the wake downstream of the rotor. Staggered vortex street downstream of the turbine was mentioned as a possible explanation for this lower peak, while the higher frequency peak was coupled to the passage of the two turbine ‘‘buckets.’’ Further analysis on turbine interaction using CFD was done by Zhang et al[17] with an increased number of turbines and a more detailed investigation of the turbulent kinetic energy (TKE) in the wake They found that one of the optimal array configurations identified by Shigetomi et al[16] was superior to the others. Two different λ were chosen to represent optimal and suboptimal operating conditions of the turbine
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