Assessing the Importance of Geometric Nonlinear Effects in the Prediction of Wind Turbine Blade Loads

2015 ◽  
Vol 10 (4) ◽  
Author(s):  
D. I. Manolas ◽  
V. A. Riziotis ◽  
S. G. Voutsinas
Keyword(s):  
Wind Turbine ◽  
Nonlinear Effects ◽  
Normal Operation ◽  
Order Model ◽  
Multibody Model ◽  
Operation Conditions ◽  
Geometric Nonlinear ◽  
Structural Nonlinearities ◽  
Clear Shift ◽  
Blade Loads

As the size of commercial wind turbines increases, new blade designs become more flexible in order to comply with the requirement for reduced weights. In normal operation conditions, flexible blades undergo large bending deflections, which exceed 10% of their radius, while significant torsion angles toward the tip of the blade are obtained, which potentially affect performance and stability. In the present paper, the effects on the loads of a wind turbine from structural nonlinearities induced by large deflections of the blades are assessed, based on simulations carried out for the NREL 5 MW wind turbine. Two nonlinear beam models, a second order (2nd order) model and a multibody model that both account for geometric nonlinear structural effects, are compared to a first order beam (1st order) model. Deflections and loads produced by finite element method based aero-elastic simulations using these three models show that the bending–torsion coupling is the main nonlinear effect that drives differences on loads. The main effect on fatigue loads is the over 100% increase of the torsion moment, having obvious implications on the design of the pitch bearings. In addition, nonlinearity leads to a clear shift in the frequencies of the second edgewise modes.

Seismic Design of a Double Deck Floating Roof Type Used for Liquid Storage Tanks

2015 ◽  
Vol 137 (4) ◽  
Author(s):  
Mohammad Ali Goudarzi
Keyword(s):  
Seismic Design ◽  
Design Procedure ◽  
Hydrodynamic Pressure ◽  
Nonlinear Effects ◽  
Vertical Displacement ◽  
Bottom Plate ◽  
Liquid Storage ◽  
Geometric Nonlinear ◽  
General Displacement ◽  
Seismic Stress

Sloshing response of a cylindrical liquid storage tank with the double deck type floating roof (DDFR) subjected to seismic excitation is considered in this paper. The aim of the paper is to clarify the significant parameters that should be considered in the seismic design of a DDFR and proposing a practical seismic design procedure for evaluating the dynamic stresses inside a DDFR. A numerical method including fluid–structure interaction and the geometry details of a DDFR tank are established. The geometric nonlinear effects on the seismic behavior of the DDFR as well as the accuracy of common analytical solution suggested in the literature are examined by the numerical model. The numerical results show that the geometric nonlinear effects can considerably reduce the seismic stress in DDFR, but have no significant effect on the liquid hydrodynamic pressure exerted on the DDFR and the roof's vertical displacement. It is also revealed that not only the general displacement of DDFR but also the local effects of liquid hydrodynamic pressure on the bottom plate should be considered for seismic design of a DDFR. Finally, a design procedure for the evaluation of dynamic stress in the DDFR due to the seismic loads is proposed and discussed.

Geometric Nonlinear Effect on Large Span Cable-Stayed Bridge

2014 ◽  
Vol 638-640 ◽  
pp. 942-946
Author(s):  
Shuang Rui Chen ◽  
Quan Sheng Yan
Keyword(s):  
Linear Method ◽  
Bending Moment ◽  
Nonlinear Effects ◽  
Element Model ◽  
Vertical Displacement ◽  
Displacement Effect ◽  
Cable Stayed Bridge ◽  
Long Span ◽  
Geometric Nonlinear ◽  
Main Girder

It is introduced that three main factors cause geometric nonlinear effects of long span cable-stayed bridge: large displacement effect, cable sag effect, and the combination of bending moment and axial force effect. The iteration method of geometrical nonlinear problem is also introduced. The bridge deformation was calculated by establishing a plane truss finite element model of a long-span single tower cable-stayed bridge under consideration of nonlinearity and compared with that done with linear method. It is concluded that nonlinearity influenced differently to the bending moment of main girder, the displacement of tower root and the vertical displacement of girder.

Multiple Crossover Effects and Nonlinear Effects on Socio-Cultural Adjustment

2004 ◽  
Author(s):  
Riki Takeuchi ◽  
David P. Lepak ◽  
Sophia Marinova ◽  
Seokhwa Yun
Keyword(s):  
Nonlinear Effects ◽  
Cultural Adjustment ◽  
Crossover Effects

Nonlinear effects in a plasma

1966 ◽  
Vol 90 (11) ◽  
pp. 435-489 ◽  
Author(s):  
Vadim N. Tsytovich
Keyword(s):  
Nonlinear Effects
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