ECIS Publications

Description

This paper describes a computer program developed for
structural dynamic analysis of horizontal axis wind
turbines (HAWTs). It is based on the finite element
method through its reliance on NASTRAN for the development of mass, stiffness, and damping matrices of
the tower and rotor, which are treated in NASTRAN as
separate structures. The tower is modeled in a stationary frame and the rotor in one rotating at a
constant angular velocity. The two structures are
subsequently joined together (external to NASTRAN)
using a time—dependent transformation consistent with
the hub configuration. Aerodynamic loads are computed
with an established flow model based on strip theory.
Aeroelastic effects are included by incorporating the
local velocity and twisting deformation of the blade
in the load computation. The turbulent nature of the
wind, both in space and time, is modeled by adding in
stochastic wind increments. The resulting equations
of motion are solved in the time domain using the
implicit Newmark—Beta integrator. Preliminary
comparisons with data from the Boeing/NASA MOD2 HAWT
indicate that the code is capable of accurately and
efficiently predicting the response of HAWTs driven
by turbulent winds.