Abstract
This is the first part of a two part paper on flow around vibrating wind turbine airfoils. In this part 1, the unsteady, incompressible, viscous and laminar flow over a forced oscillating airfoil is computed using a method based on a commercial Computational Fluid Dynamics (CFD) code. Beforehand, the Navier-Stokes equations are solved for the unsteady flow around a NACA 0012 airfoil at a fixed 20° incidence and the low Reynolds numbers of 103 and 104 to check the reliability of the CFD computations. Then the flow around a pitching airfoil is simulated for prescribed values of the reduced frequency. The Navier-Stokes equations are expressed in ALE formulation and solved with moving mesh. The effects of the discretization scheme and the moving mesh technique are investigated. The hysteresis loops of the dynamic stall phenomenon are highlighted.
Highlights
Wind turbines are subjected to a hard environment as the atmospheric turbulence, the ground boundary layer, the rapid variations in wind speed and direction and the tower shadow for downwind turbine
To check the meshing technique implemented for moving the grid, results are compared to that obtained with the Arbitrary Sliding Interface (ASI) method which is built-in the Computational Fluid Dynamics (CFD) code
SUMMARY AND CONCLUSION Simulations of the fluid flow around an airfoil in forced pitch oscillations have been performed with a commercial CFD code based on the solution of the Navier-Stokes equations by the finite volume method
Summary
Wind turbines are subjected to a hard environment as the atmospheric turbulence, the ground boundary layer, the rapid variations in wind speed and direction and the tower shadow for downwind turbine. Problems of aeroelastic stability can be encountered in particular on the new large wind turbine blades. Numerical simulation of the flow around oscillating wind turbine airfoils flow and of elastic body deformation were studied separately. These weak coupled approaches are limited to small deformations. The problem of classical Flutter phenomenon is dealt with a strong coupled method where the dynamic response of the wind turbine blade is determined in time accurate sequences. Beforehand, to check the reliability of the CFD computations, the cases of the unsteady flow field around (i) a NACA 0012 airfoil at a fixed large angle of attack and (ii) around this airfoil in forced pitch oscillations are considered. The problems of flow induced vibrations of a symmetrical NACA 0012 airfoil in pitch oscillations and that of a cambered NACA 632 415 airfoil in flutter are considered in the part 2 of the present paper
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