Effects of large bending deflections on blade flutter limits

ISSN 0106-2840 The coupling of bending and torsion due to large blade bending are assumed to have some effects of the flutter limits of wind turbines [1]. In the present report, the aeroelastic blade model suggested by Kallesøe [2], which is similar to the second order model used in [3], is used to investigate the aeroelastic stability limits of the RWT blade with and without the effects of the large blade deflection. The investigation shows no significant change of the flutter limit on the rotor speed due to the blade deflection, whereas the first edgewise bending mode becomes negatively damped due to the coupling with blade torsion which causes a change of the effective direction of blade vibration. These observations are confirmed by nonlinear aeroelastic simulations using HAWC2 [4, 5]. This work is part of the UpWind project funded by the European Commission under the contract number SES6-CT-2005-019945 which is gratefully acknowledged. This report is the deliverable D2.3 of the UpWind project. ISBN 978-87-550-3665-9 Contract no.: SES6-CT-2005-019945 Group’s own reg. no.: 1110053-01 Sponsorship: European Commission