Session: 01-11-02: Wind Energy

Paper Number: 110506

110506 - Comparison Between 1d Beam Model With 2d Cross-Sectional Analysis and 3d Fea Model for Wind Blade 

Wind energy has been an indispensable part of green energy. To increase the efficiency and power generation of wind turbines, wind blades have been growing larger and larger in diameter over the years. However, this growth of wind blades brings up design issues, and the stresses inside the wind blade also become complicated. Moreover, to increase the specific stiffness and strength of wind blades, uni-directional composite materials are used, thus bringing complicated anisotropic properties and heterogeneity into the 3D FEA model and structure analysis.

Due to the limitation of the computation resources, in the system-level simulation, 1D beam analysis instead of a completed 3D FEA model is used. To convert the complete 3D FEA model into a 1D beam model, the most widely used technique used in industries is to cut the wind blade 3D FEA model into multiple 2D cross-sections, and then do the beam cross-sectional analyses to get the Timoshenko beam properties, which would be input into beam elements in the 1D beam analysis later. After completion of the system-level simulation, the response would be an input into the dehomogenization of the 2D cross-sectional analysis to get the 3D stress. The computation resources needed in this method are much less than the corresponding 3D FEA model.

The mechanics theory behind combining 1D analysis with 2D cross-sectional analysis, however, is derived based on the assumption that the blade is made of piecewise constant cross-section along the spanwise direction. The geometry of the wind blade changes along the spanwise direction, thus violates this assumption. As a result, the accuracy of the 1D beam analysis with beam properties from 2D cross-sectional analyses would not be accurate. None of the research has carefully investigated the accuracy of this 1D beam analysis method in comparison to the original 3D FEA.

To investigate the accuracy of system-level analysis with beam properties generated from beam analyses, we would build a full 3D FEA model with at least one solid element for each layer. Compared with 3D FEA model with shell elements, the solid element would have less assumptions and thus more accuracy. We would get detailed 3D stress from critical loading on the 3D FEA model. There, we compare the displacement along the reference line, and recovered 3D stresses, from system-level analysis with beam properties calculated by VABS, which is a popular commercial software for beam analysis in industries. We would be able to benchmark the accuracy of 1D beam analysis with 2D beam cross-section analysis. Furthermore, we will also compare the results of 3D FEA using solids and other approaches used in the literature including FEA using shell elements, and FEA using composite solid elements, etc.

Presenting Author: Akshat Bagla Purdue University

Presenting Author Biography: Akshat is working on finite element modeling of shell or plate structures using the Mechanics of Structure Genome (MSG) theory at Purdue University. He has experience working on damage modeling of prepreg-based discontinuous composites and Z-pinned laminates at IIT Kanpur, India. He has contributed to solar street light modeling for rural and industrial applications during his internship at the administrative office in Ranchi, India. His research interests are solid mechanics and composite structures.

Authors:

Rong Chiu Purdue University
Akshat Bagla Purdue University
Wenbin Yu Purdue University