Parametric study on impact of delamination on flutter velocity of wind turbine blade structure

Abstract

Classical aeroelastic flutter of wind turbine blades is a critical subject caused by the coalescence of flap wise and torsion modes due to which the structural and aerodynamic damping is insufficient to damp out the large vibratory motion produced. Although it is inconsequential for the current utility scale wind turbine blades, the crescent need for light weight and longer blades seems to enhance the significance by considering this phenomenon. This would mean that such aeroelastic instabilities would become a major design drivers. This study is performed to detect the occurrence of flutter instability and its dependency of delamination in a horizontal axis wind turbine (HAWT) blade In addition, the impact of the process parameters on the flutter performance and aeroelastic stability of the blade is investigated. A 100m HAWT blade with DU-97-W-300 aerofoil cross section is chosen for the analysis where an advanced ideal beam model is used as an idealised structure to represent its structure. The analysis is carried out with the help of standard FEA codes using PK-method for flutter solution and Double lattice method to calculate the aerodynamic loads and matrices, while the equations of motion are solved using by Galerkin approach. The output highlights the change in damping ratio due to isolation of skin regions due to glue failure and the change in the impact of delamination with respect to wind speed is also observed. The results reveal a decline in flutter velocity indicating, decrease in blade stability due to local failure in blade structure.