Development of an anisotropic beam finite element for composite wind turbine blades in multibody system

Abstract

Link back to DTU OrbitCitation (APA): Kim, T., Hansen, A. M., & Branner, K. (2013 ABSTRACTIn this paper a new anisotropic beam finite element for composite wind turbine blades is developed and implemented into the aeroelastic nonlinear multibody code, HAWC2, intended to be used to investigate if use of anisotropic material layups in wind turbine blades can be tailored for improved performance such as reduction of loads and/or increased power capture. The element stiffness and mass matrices are first derived based on pre-calculated anisotropic beam properties, and the beam element is subsequently put into a floating frame of reference to enable full rigid body displacement and rotation of the beam. This derivation provides the mass and stiffness properties and the fictitious forces needed for implementation into HAWC2. The implementation is subsequently validated by running three validation cases which all show good agreement with results obtained by other authors. Further, a parametric study is conducted in order to investigate if the given anisotropic effect of the composite blade, bend-twist coupling effect, is able to be examined by the developed beam element in a multibody system or not. Two different coupled examples of bend-twist coupling for the blade of a 5MW fictitious wind turbine are considered. The two cases differ in the amount of bend-twist coupling introduced into the blade so that they produce 0.3deg and 1deg twist at the blade tip (towards feather), respectively, for a 1m flapwise tip deflection towards the tower. It is examined if the current structural model is able to capture the anisotropic effects in a multibody system.

Modal properties and stability of bend–twist coupled wind turbine blades

“…The aeroelastic modal properties and stability limits of both edge-and flap-twist coupled blades are investigated by means of eigenvalue analysis around a steady-state equilibrium using the aero-servoelastic tool HAWCStab2. For the analysis with fully coupled cross-section stiffness matrices the beam element of Kim et al (2013) has been implemented in HAWCStab2.…”

“…To allow for the analysis of anisotropic cross-sectional properties the beam element proposed by Kim et al (2013) has been implemented into HAWCStab2. The two-noded element assumes polynomial shape functions of arbitrary order where the shape function coefficients are eliminated by minimizing the elastic energy of the beam while satisfying the boundary conditions.…”

Timoshenko Beam Element With Anisotropic Cross-Sectional Properties

“…The beam is 2.54 m long, has a height of 16 The cantilever was discretised with 16 elements. In Table 1 the results of the present model are compared with beam models by Hodges et al [9] and Armanios and Badir [11] as well as a finite element shell model by Kim et al [5].…”

“…Ghiringhelli's [4] element formulation uses the cross-section compliance matrix and beam forces, which vary linearly along length, to obtain the element stiffness by principle of virtual forces. The two-noded element of Kim et al [5] assumes polynomial shape functions of arbitrary order. The shape function coefficients are determined by minimizing the elastic energy of the beam while satisfying the boundary conditions.…”

“…The anisotropic, corotational Timoshenko beam element is validated against natural frequencies and several static cases of previous works. A new test case with a coupled 45-degree bend cantilever is also proposed and compared to results obtained with the beam element by Kim et al [5].…”