Modal response of 3-bladed wind turbines

A. set of linear equations describing the motion of an operating 3-bladed HAWT is obtained from the dynamic characteristics of the stationary turbine by adding rotating frame effects. The approach makes use of the Coleman multi-blade transformation to present all results relative to the fixed frame. The formulation is in terms of a selected number of stationary, real mode shapes. The formulation is applied to the expression of both the aerodynamic loading and the displacement response in terms of the complex operating mode shapes. The technique is demonstrated on a hypothetical 46-m wind turbine subject to vertical wind shear The principal objective of the paper is to enable the characteristics of the inflow to be related to the nature of the response. A second objective is to illustrate a method of extracting linearized models from general aeroelastic codes such as ADAMS(TM).