Performance and wake of a Savonius vertical‐axis wind turbine under different incoming conditions

Abstract

In 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.

Flow field and performance of a vertical-axis wind turbine on model buildings

“…The control of the tip speed ratio was fixed between different measurement positions leading to slight variations between 0.62 and 0.78. The values are in line with expected values for Savonius-type turbines (Akwa et al, 2012;Aliferis et al, 2019).…”

Near-wake structure of full-scale vertical-axis wind turbines

“…Aliferis et al. (2019) studied the 2-D planar wake structure of a Savonius-type VAWT with helical blades using a Cobra probe on a traverse. Lastly, Ouro et al.…”

“…Schuerich & Brown (2011) used a vorticity-transport model for this purpose, and Cheng et al (2017) approached the problem using unsteady RANS, 2-D LES and wind-tunnel experiments. Aliferis et al (2019) studied the 2-D planar wake structure of a Savonius-type VAWT with helical blades using a Cobra probe on a traverse. Lastly, Ouro et al (2019) analysed turbulence quantities in the wake of a helical-bladed VAWT in a water channel using pointwise velocity measurements from an anemometer on a traverse.…”

Numerical Study of a Novel Concept for Manufacturing Savonius Turbines with Twisted Blades

“…Moreover, SAWINT is the only studied turbine with a small end plate area (its geometric design is made for ice breaking in extreme cold conditions), causing fluid leakage from the concave side of the blade to the external flow, dramatically affecting its aerodynamic performance [15]. The wake is deflected in the same direction where the blades move opposite to the flow, as it was in [12].…”

“…Experimentally, Damak et al [10] and Saha et al [11] further revealed the potential that the twisted bladed rotor possesses as compared to the conventional Savonius turbine under specific conditions. The wake from the turbine with helical configuration, experimentally investigated by Aliferis et al [12], was found to be asymmetrical and deflected to the side where the blade moves in the opposite direction to the incoming wind. Kumar and Saini [13] carried out a numerical analysis aiming to optimize the blade twist angle of a Savonius hydrokinetic turbine.…”