Computation of Modal Aerodynamic Damping Using CFD

2003 ◽  
Author(s):  
F. Bertagnolio ◽  
M. Gaunaa ◽  
N. N. So̸rensen ◽  
M. Hansen ◽  
F. Rasmussen
Keyword(s):  
Wind Turbine ◽  
Structural Model ◽  
Turbine Rotor ◽  
Dynamic Stall ◽  
Navier Stokes ◽  
Test Cases ◽  
Flow Solver ◽  
Aerodynamic Damping ◽  
Semi Empirical ◽  
Wind Turbine Rotor

This work focuses on the numerical evaluation of aerodynamic damping for a wind turbine rotor. A finite beam element code is used to describe the structure. Two types of aerodynamic models are compared. Firstly, two engineering semi-empirical dynamic stall models implemented in the structural code for modelling the aerodynamic forces are applied. Secondly, a Navier-Stokes flow solver has been coupled to the structural model. Test cases involving a two-bladed wind turbine rotor are computed. The aerodynamic damping is determined for the two first eigenmodes of the structure. A comparison study of the results highlights the discrepancies between the different models.

Navier-Stokes and Comprehensive Analysis Performance Predictions of the NREL Phase VI Experiment

2003 ◽  
Author(s):  
Earl P. N. Duque ◽  
Michael D. Burklund ◽  
Wayne Johnson
Keyword(s):  
Experimental Data ◽  
Wind Turbine ◽  
Turbine Rotor ◽  
Operating Conditions ◽  
Navier Stokes ◽  
Horizontal Axis Wind Turbine ◽  
Performance Predictions ◽  
Nasa Ames Research ◽  
Nrel Phase Vi ◽  
Wind Turbine Rotor

A vortex lattice code, CAMRAD II, and a Reynolds-Averaged Navier-Stoke code, OVERFLOW-D2, were used to predict the aerodynamic performance of a two-bladed horizontal axis wind turbine. All computations were compared with experimental data that was collected at the NASA Ames Research Center 80-by 120-Foot Wind Tunnel. Computations were performed for both axial as well as yawed operating conditions. Various stall delay models and dynamics stall models were used by the CAMRAD II code. Comparisons between the experimental data and computed aerodynamic loads show that the OVERFLOW-D2 code can accurately predict the power and spanwise loading of a wind turbine rotor.

Vibrations of a Three-Bladed Wind Turbine Rotor Due to Classical Flutter

2002 ◽  
Author(s):  
M. H. Hansen
Keyword(s):  
Wind Turbine ◽  
Critical Frequency ◽  
Turbine Blades ◽  
Turbine Rotor ◽  
Normal Operation ◽  
Aerodynamic Damping ◽  
Operation Conditions ◽  
Torsional Frequency ◽  
Classical Flutter ◽  
Wind Turbine Rotor

The aeroelastic stability of a three-bladed wind turbine is considered with respect to classical flutter. Previous studies have shown that the risk of stall-induced vibrations of turbine blades is related to the dynamics of the complete turbine, for example does the aerodynamic damping of a rotor whirling mode depend highly on the tower stiffness. The results of this paper indicate that the turbine dynamics also affect the risk of flutter. The study is based on an eigenvalue analysis of a linear aeroelastic turbine model. In an example of a MW sized turbine, the critical frequency of the first torsional blade mode is determined for which flutter can occur under normal operation conditions. It is shown that this critical torsional frequency is higher when the blades are interacting through the hub with the remaining turbine, than when all blades are rigidly clamped at the root. Thus, the dynamics of the turbine has increased the risk of flutter.

Development of a Wind Tunnel Test Apparatus for Horizontal Axis Wind Turbine Rotor Testing

2008 ◽  
Author(s):  
Michael McWillam ◽  
David Johnson
Keyword(s):  
Wind Tunnel ◽  
Wind Turbine ◽  
Wind Turbines ◽  
High Speed ◽  
Turbine Rotor ◽  
Dynamic Stall ◽  
Flow Structures ◽  
Horizontal Axis Wind Turbine ◽  
Wind Turbine Rotor ◽  
Blade Geometry

The engineering of wind turbines is not fully mature. There are still phenomena, particularly dynamic stall that cannot be accurately modeled. Dynamic stall contributes to fatigue stress and premature failure in many turbine components. The three dimensionality of dynamic stall make these structures unique for wind turbines. Currently flow visualization of dynamic stall on a wind turbine rotor has not been achieved, but these visualizations can reveal a great deal about the structures that contribute to dynamic stall. Particle Image Velocimetry (PIV) is a powerful experimental technique that can take non-intrusive flow measurements of planar flow simultaneously. High-speed cameras enable time resolved PIV can reveal the transient development. This technique is suited to gain a better understanding of dynamic stall. A custom 3.27 m diameter wind turbine has been built to allow such measurements on the blade. The camera is mounted on the hub and will take measurements within the rotating domain. Mirrors are used so that laser illumination rotates with the blade. The wind turbine will operate in controlled conditions provided by a large wind tunnel. High-speed pressure data acquisition will be used in conjunction with PIV to get an understanding of the forces associated with the flow structures. Many experiments will be made possible by this apparatus. First the flow structures responsible for the forces can be identified. Quantitative measurements of the flow field will identify the development of the stall vortex. The quantified flow structures can be used to verify and improve models. The spatial resolution of PIV can map the three dimensional structure in great detail. The experimental apparatus is independent of the blade geometry; as such multiple blades can be used to identify the effect of blade geometry. Finally flow control research in the field of aviation can be applied to control dynamic stall. These experiments will be subject of much of the future work at the University of Waterloo. Potentially this work will unlock the secrets of dynamic stall and improve the integrity of wind turbines.

Optimization of the Taper/Twist Stacking Axis Location of NREL VI Wind Turbine Rotor Blade Using Neural Networks Based on Computational Fluid Dynamics Analyses

2018 ◽  
Vol 141 (1) ◽  
Author(s):  
Mustafa Kaya ◽  
Munir Elfarra
Keyword(s):  
Fluid Dynamics ◽  
Neural Networks ◽  
Computational Fluid Dynamics ◽  
Wind Turbine ◽  
Turbine Blade ◽  
Turbine Rotor ◽  
Wind Turbine Blade ◽  
Navier Stokes ◽  
Flow Solver ◽  
Turbine Rotor Blade

The stacking axis locations for twist and taper distributions along the span of a wind turbine blade are optimized to maximize the rotor torque and/or to minimize the thrust. A neural networks (NN)-based model is trained for the torque and thrust values calculated using a computational fluid dynamics (CFD) solver. Once the model is obtained, constrained and unconstrained optimization is conducted. The constraints are the torque or the thrust values of the baseline turbine blade. The baseline blade is selected as the wind turbine blade used in the National Renewable Energy Laboratory (NREL) Phase VI rotor model. The Reynolds averaged Navier–Stokes (RANS) computations are done using the FINE/turbo flow solver developed by NUMECA International. The k-epsilon turbulence model is used to calculate the eddy viscosity. It is observed that achieving the same torque value as the baseline value is possible with about 5% less thrust. Similarly, the torque is increased by about 4.5% while maintaining the baseline thrust value.

Harmonization of new wind turbine rotor blades development process: A review

2014 ◽  
Vol 39 ◽  
pp. 874-882 ◽  
Author(s):  
B. Rašuo ◽  
M. Dinulović ◽  
A. Veg ◽  
A. Grbović ◽  
A. Bengin
Keyword(s):  
Wind Turbine ◽  
Development Process ◽  
Turbine Rotor ◽  
Rotor Blades ◽  
Wind Turbine Rotor

Prediction of Wind Turbine Rotor Loads Using the Beddoes-Leishman Model for Dynamic Stall

1995 ◽  
Vol 117 (3) ◽  
pp. 200-204 ◽  
Author(s):  
K. Pierce ◽  
A. C. Hansen
Keyword(s):  
Wind Turbines ◽  
Aerodynamic Force ◽  
Unsteady Aerodynamics ◽  
Turbine Rotor ◽  
Dynamic Stall ◽  
University Of Utah ◽  
Horizontal Axis Wind Turbines ◽  
Wind Tunnel Data ◽  
The University ◽  
Wind Turbine Rotor

The Beddoes-Leishman model for unsteady aerodynamics and dynamic stall has recently been implemented in YawDyn, a rotor analysis code developed at the University of Utah for the study of yaw loads and motions of horizontal axis wind turbines. This paper presents results obtained from validation efforts for the Beddoes model. Comparisons of predicted aerodynamic force coefficients with wind tunnel data and data from the combined experiment rotor are presented. Also, yaw motion comparisons with the combined experiment rotor are presented. In general the comparisons with the measured data are good, indicating that the model is appropriate for the conditions encountered by wind turbines.

Design and analysis of a segmented blade for a 50 MW wind turbine rotor

2022 ◽  
pp. 0309524X2110693
Author(s):  
Alejandra S Escalera Mendoza ◽  
Shulong Yao ◽  
Mayank Chetan ◽  
Daniel Todd Griffith
Keyword(s):  
Wind Turbine ◽  
Large Mass ◽  
Turbine Rotor ◽  
Bolted Joints ◽  
Bonded Joints ◽  
Sheer Size ◽  
Extreme Scale ◽  
The Impact ◽  
Adhesive Materials ◽  
Wind Turbine Rotor

Extreme-size wind turbines face logistical challenges due to their sheer size. A solution, segmentation, is examined for an extreme-scale 50 MW wind turbine with 250 m blades using a systematic approach. Segmentation poses challenges regarding minimizing joint mass, transferring loads between segments and logistics. We investigate the feasibility of segmenting a 250 m blade by developing design methods and analyzing the impact of segmentation on the blade mass and blade frequencies. This investigation considers various variables such as joint types (bolted and bonded), adhesive materials, joint locations, number of joints and taper ratios (ply dropping). Segmentation increases blade mass by 4.1%–62% with bolted joints and by 0.4%–3.6% with bonded joints for taper ratios up to 1:10. Cases with large mass growth significantly reduce blade frequencies potentially challenging the control design. We show that segmentation of an extreme-scale blade is possible but mass reduction is necessary to improve its feasibility.

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