Numerical simulation of the flow around oscillating wind turbine airfoils Part 2: Free vibrating airfoil

The present paper is Part 2 of a two parts paper on flow around vibrating wind turbine airfoils. The first part of the paper dealt with a forced oscillating airfoil. Part 2 focuses on free vibrating airfoils. The flow induced vibrations on two airfoils used for wind turbine blades are investigated by applying a fluid structure interaction approach. A commercial Computational Fluid Dynamics (CFD) code is coupled to a computational structural program that solves the dynamic equations of the airfoil oscillations. The fluid governing equations are described in the Arbitrary Lagrangian Eulerian coordinates and solved with a moving mesh. A straightforward meshing technique is implemented in a subroutine called by the CFD code at each time step for updating the grid. The method is applied to a free pitch oscillating airfoil and to combined pitch and vertical oscillations known as the flutter instability.