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

Highlights

Direct Numerical Simulation is performed on a Savonius style wind turbine blade.

A high order spectral element method is used.

Centrifugal instability occurs at the pressure side of the blade.

The break down of Görtler vortices cause the flow to transit to turbulence.

The pressure and friction distributions along the blade are altered by the transition phenomena.

Abstract

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 (Reξ=9×104), 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 Görtler 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.

Keywords

  • Direct Numerical Simulation;
  • Savonius style wind turbine;
  • Centrifugal instability;
  • Blade performance

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