This report contains a description of a structural damping model for Timoshenko beam elements used in the aeroelastic code HawC developed at Risø for modeling wind turbines. The model has been developed to enable modeling of turbine blades which oftenhave different damping characteristics for ¤flapwise¤, ¤edgewise¤ and ¤torsional¤ vibrations. The structural damping forces acting on the beam element are modeled by viscous damping described by an element damping matrix. The composition of this matrix is basedon the element mass and stiffness matrices. It is shown how the coefficients for the mass and stiffness contributions can be calibrated to give the desired modal damping in the complete model of a blade.
Vindenergi og atmosfæriske processer; Risø-R-1267; Risø-R-1267(EN)