Timoshenko Beam Element With Anisotropic Cross-Sectional Properties

Stäblein, Alexander R.; Hansen, Morten Hartvig

doi:10.7712/100016.2377.9780

Cited by 9 publications

(15 citation statements)

References 16 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Until recently, HAWCStab2 did not allow for the analysis of material coupled blades. A Timoshenko beam formulation that accounts for fully coupled cross section matrices has therefore been derived and implemented [6]. Bend-twist coupling was introduced by means of a coupling coefficient in the cross-sectional stiffness matrix of the blade as proposed by Lobitz and Veers [7].…”

mentioning

confidence: 99%

Using Pretwist to Reduce Power Loss of Bend-Twist Coupled Blades

Stäblein

Tibaldi

Hansen

2016

34th Wind Energy Symposium

Self Cite

View full text Add to dashboard Cite

Bend-twist coupling of wind turbine blades is known as a means to reduce the structural loads of the turbine. While the load reduction is desirable, bend-twist coupling also leads to a decrease in the annual energy production of the turbine. The reduction is mainly related to a no longer optimal twist distribution along the blade due to the coupling induced twist. Some of the power loss can be compensated by pretwisting the blade. This paper presents a pretwisting procedure for large blade deflections and investigates the effect of pretwisting on blade geometry, annual energy production, and fatigue load for the DTU 10 MW Reference Wind Turbine. The analysis was carried out by calculating the nonlinear steady state rotor deflection in an uniform inflow over the operational range of the turbine. The steady state power curve together with a Rayleigh wind speed distribution has been used to estimate the annual energy production. The turbine model was then linearised around the steady state and the power spectral density of the blade response, which was computed from transfer functions and the wind speed variations in the frequency domain, was used to estimate the fatigue loads by a spectral method.

show abstract

mentioning

confidence: 99%

Using Pretwist to Reduce Power Loss of Bend-Twist Coupled Blades

Stäblein

Tibaldi

Hansen

2016

34th Wind Energy Symposium

Self Cite

View full text Add to dashboard Cite

show abstract

“…Kim et al (2013) present a beam element assuming polynomial shape functions of arbitrary order where the shape function coefficients are eliminated by minimizing the elastic energy of the beam. The element by Stäblein and Hansen (2016) is an extension of a Timoshenko beam element by Bazoune et al (2003) to allow for the analysis of anisotropic cross-sectional properties. The formulations by Kim et al (2013) and Stäblein and Hansen (2016) assume small displacements and are intended for the application in a co-rotational or multibody formulation.…”

Section: Large Displacementsmentioning

confidence: 99%

Analysis and Design of Bend-Twist Coupled Wind Turbine Blades

Stäblein

2016

Mare-Wint

Self Cite

View full text Add to dashboard Cite

Bend-twist coupling allows wind turbine blades to self-alleviate sudden inflow changes, as in gusty or turbulent conditions, resulting in reduced ultimate and fatigue loads. If the coupling is introduced by changing the fibre direction of the anisotropic blade material, the assumptions of classical beam theory are not necessarily valid. This chapter reviews the effects of anisotropic material on the structural response of beams and identifies those relevant for wind turbine blade analysis. A framework suitable for the structural analysis of wind turbine blades is proposed and guidance for the design of bend-twist coupled blades is given.

show abstract

“…Table 3 shows the tip displacement of the uncoupled beam compared to results by Simo and Vu-Quoc (1986). And the coupled beam compared to results of a Timoshenko beam element with anisotropic cross-sectional properties by Stäblein and Hansen (2016).…”

Section: Bend Cantilevermentioning

confidence: 99%

Modal Properties and Stability of Bend-Twist Coupled Wind Turbine Blades

Stäblein¹,

Hansen²,

Verelst³

2016

Preprint

Self Cite

View full text Add to dashboard Cite

Coupling between bending and twist has a significant influence on the aeroelastic response of wind turbine blades. The coupling can arise from the blade geometry (e.g. sweep, prebending, or deflection under load) or from the anisotropic properties of the blade material. Bend-twist coupling can be utilized to reduce the fatigue loads of wind turbine blades. In this study the effects of material-based coupling on the aeroelastic modal properties and stability limits of the DTU 10 MW Reference Wind Turbine are investigated. The modal properties are determined by means of eigenvalue analysis around a steady-state equilibrium using the aero-servo-elastic tool HAWCStab2 which has been extended by a beam element that allows for fully coupled cross-sectional properties. Bend-twist coupling is introduced in the cross-sectional stiffness matrix by means of coupling coefficients that introduce twist for flapwise (flap-twist coupling) or edgewise (edge-twist coupling) bending. Edge-twist coupling can increase or decrease the damping of the edgewise mode relative to the reference blade, depending on the operational condition of the turbine. Edge-twist to feather coupling for edgewise deflection towards the leading edge reduces the inflow speed at which the blade becomes unstable. Flap-twist to feather coupling for flapwise deflections towards the suction side increase the frequency and reduce damping of the flapwise mode. Flap-twist to stall reduces frequency and increases damping. The reduction of blade root flapwise and tower bottom fore-aft moments due to variations in mean wind speed of a flap-twist to feather blade are confirmed by frequency response functions.Published by Copernicus Publications on behalf of the European Academy of Wind Energy e.V.

show abstract

Timoshenko Beam Element With Anisotropic Cross-Sectional Properties

Cited by 9 publications

References 16 publications

Using Pretwist to Reduce Power Loss of Bend-Twist Coupled Blades

Using Pretwist to Reduce Power Loss of Bend-Twist Coupled Blades

Analysis and Design of Bend-Twist Coupled Wind Turbine Blades

Modal Properties and Stability of Bend-Twist Coupled Wind Turbine Blades

Contact Info

Product

Resources

About