Direct Numerical Simulation of flow instabilities over Savonius style wind turbine blades

In this paper, Direct Numerical Simulations (DNS) are carried out in order to capture the flow instabilities and transition to turbulence occurring on a Savonius style wind turbine (SSWT) blade. Simulations are conducted with the open source code NEK5000, solving the incompressible Navier-Stokes equations with a high order, spectral element method. Because of the relatively high Reynolds number considered (Re xi = 9 x 10(4)), the computational domain of the Savonius blade is reduced to the pressure side, and the blade is studied in static condition, which avoids the large scale vortex shedding that occurs on its suction side, particularly allows to investigate the static performance of the wind turbine. The results suggest that Gortler vortices can occur and cause the flow to transit to turbulence, which modify the pressure and wall friction distributions, and consequently alter the drag and lift forces. (C) 2016 Elsevier Ltd. All rights reserved.