Application of a turbulent vortex core model in the free vortex wake scheme to predict wind turbine aerodynamics

Abstract

Developing suitably generalized models of rotor blade vortices that accurately predict their evolution continues to be a challenge for wind turbine analysis. The choice of vortex core model in a free vortex wake (FVW) method is essential to accurately predict rotor aerodynamic performance. In this work, a turbulent vortex core model (β-Vatistas model) was considered and improved. A formula was developed that approximates the key parameter β, which represents the degree of turbulence in the β-Vatistas model. The improved β-Vatistas model was used in the FVW model, and the β value was calculated based on the tip vortex circulation in each iteration. The wake flow characteristic and low speed shaft torque were calculated using the FVW model coupled with the turbulent vortex core model or two laminar vortex core models. The use of the improved β-Vatistas model provided smaller maximum vorticities at the rolled-up angle and a slower dissipation speed of the tip vortex than those calculated by two laminar vortex core models. The FVW model with the improved β-Vatistas model can accurately capture the tip vortex positions, either in the near wake or in the far wake. The results indicate that the application of the β-Vatistas turbulent vortex core model in the FVW model is feasible and can better capture the wake structure than the laminar vortex core models.