Eventos Anais de eventos
COBEM 2023
27th International Congress of Mechanical Engineering
Numerical Analysis of the Blade and Tower Aerodynamics of the NREL 5 MW Wind Tower Project
Submission Author:
Augusto Bornschlegell , MS
Co-Authors:
Vinícius Massoni Pires, Reginaldo Ribeiro Sousa, Bruno Arantes Moreira, Augusto Bornschlegell
Presenter: Augusto Bornschlegell
doi://10.26678/ABCM.COBEM2023.COB2023-0090
Abstract
Wind turbines has increasingly been studied in order to provide technical solutions to the challenges in converting eolian energy into electricity. Among these different challenges, the blades' aerodynamics has to be optimized and data related to these geometries are normally confidential. The NREL 5 MW project is a available study case (i.e. a benchmark) with detailed information about the blade geometry. As the blade rotates, a control system adjust the blade's angle of attack in order to maximize energy conversion as well as to avoid overload to its structure. When the blade's tip is at the lowest point, the blade is aligned with the tower. Thus, the blade aerodynamics may experience a different behavior. In this work, we evaluate flow behavior or the NREL blade when it is far away from the tower and when it is just in front of the tower. To attain this task, o numerical 2D model, covering the blade mid plane cross section, was developed. We used the pisoFoam solver from OpenFOAM v8. The numerical schemes employed were backward second order for time integration, upwind second order for the advective terms treatment and PISO algorithm for the pressure-velocity coupling. As boundary conditions, the velocity of 20 m/s is imposed at the inlet and the slip condition at the top and bottom limits. These configuration led to Reynolds Number of 9.6x104. At the blade and tower surfaces, the non-slip boundary condition was applied. The domain discretization was performed with the blockMesh and snappHexMesh solvers from OpenFoam. The GCI method was employed to verify the results sensibility to the mesh. The final mesh has 430 k cells, which 426 k are hexahedra and 4 k are polyhedra (3.4 k with 7 faces and 0.6 k with 8 faces). The standard values of the aerodynamic coefficients are in good agreement with the results obtained with the proposed model. The results regarding the blade far from the tower (case A) and the blade in from of the tower (case B) can be summarized as follows. The flow behavior in case A is stead whereas in case B, it presents a sinusoidal behavior at 2 Hz. The aerodynamic forces was increased by 25% in magnitude in case B. Then, we could conclude that the presence of the tower affects not only the aerodynamic forces magnitude, but also its behavior over time.
Keywords
wind turbine, CFD Simulation using OpenFoam, Grid Convergence Index (GCI), NREL 5 MW
