Modelling of unsteady airfoil aerodynamics for the prediction of blade standstill vibrations

In the present work, CFD simulations of the DU96-W-180 airfoil at 26 and 24 deg. angles of attack were performed. 2D RANS and 3D DES computations with non-moving and prescribed motion airfoil suspensions were carried out. The openings of the lift coefficient loops predicted by CFD were different than those predicted by engineering models.

The average lift slope of the loops from the 3D CFD had opposite sign than the one from 2D CFD. Trying to model the 3D behaviour with the engineering models proved difficult. The disagreement between the 2D CFD, 3D CFD and the engineering models indicates that further investigations are needed and that caution should be taken when applying engineering models in connection with aeroelastic simulations.

Nonetheless, the results of the 2D CFD, 3D CFD and the engineering models indicate that the associated aerodynamic damping may be higher than that predicted by state of the art aeroelastic codes.