Aerodynamic Characteristics of a Single Airfoil for Vertical Axis Wind Turbine Blades and Performance Prediction of Wind Turbines

Abstract

The design of wind turbines requires a deep insight into their complex aerodynamics, such as dynamic stall of a single airfoil and flow vortices. The calculation of the aerodynamic forces on the wind turbine blade at different angles of attack (AOAs) is a fundamental task in the design of the blades. The accurate and efficient calculation of aerodynamic forces (lift and drag) and the prediction of stall of an airfoil are challenging tasks. Computational fluid dynamics (CFD) is able to provide a better understanding of complex flows induced by the rotation of wind turbine blades. A numerical simulation is carried out to determine the aerodynamic characteristics of a single airfoil in a wide range of conditions. Reynolds-averaged Navier–Stokes (RANS) equations and large-eddy simulation (LES) results of flow over a single NACA0012 airfoil are presented in a wide range of AOAs from low lift through stall. Due to the symmetrical nature of airfoils, and also to reduce computational cost, the RANS simulation is performed in the 2D domain. However, the 3D domain is used for the LES calculations with periodical boundary conditions in the spanwise direction. The results obtained are verified and validated against experimental and computational data from previous works. The comparisons of LES and RANS results demonstrate that the RANS model considerably overpredicts the lift and drag of the airfoil at post-stall AOAs because the RANS model is not able to reproduce vorticity diffusion and the formation of the vortex. LES calculations offer good agreement with the experimental measurements.

Numerical Calculation Method of Spanwise Icing Characteristics and Performance Loss of Three-Dimensional Vertical Axis Wind Turbine Blades

“…The aerodynamic performance of the blade is more sensitive to geometrical changes in the leading edge of the airfoil; so, other components such as struts are not considered. The fluid domain boundary does not interfere with the flow state around the blade, and the minimum dimension is 20 times the chord length [14]. The computational domain includes the blade model established by the NACA0018 airfoil, and the span length is 0.5 m. The fluid domain is divided into structural meshes by C-type segmentation, and the blade end meshes are refined by O-type segmentation to ensure the orthogonality of the end meshes, as shown in Figures 2 and 3.…”

Control of Aerodynamic Characteristics of Thick Airfoils at Low Reynolds Numbers Using Methods of Boundary Layer Control

“…The SST model offers significant benefits compared to the RNG and realizable versions from the k-ε family of models. Additionally, it outperforms the Spalart-Allmaras eddy viscosity model, which uses either the vorticity model or the modulus of the strain rate tensor to compute eddy viscosity as well as the V2F four-parameter model [29].…”

Control of Aerodynamic Characteristics of Thick Airfoils at Low Reynolds Numbers Using Energy Methods

“…The SST model is a generalization of two turbulence models: the k-ε model in the shear flow region far from the wall and the k-ω model in the near-wall region. SST model has significant advantages over the models of the k-ε family (RNG and Realizable versions), Spalart-Allmaras eddy viscosity model (the vorticity model or the modulus of the strain rate tensor is used to calculate the eddy viscosity), and the four-parameter model V2F [24]. In the range of angles of attack from 40 • to 135 • , the pulsations of the longitudinal force are approximately 30% of the maximum load on the airfoil, and the maximum pulsations of the transverse force at an angle of attack of 135 • are of the same order with the largest transverse force acting on the airfoil.…”