An Algorithm for Preliminary Aeroelastic Analysis of Composite Wind Turbine Blades

Abstract

Determining the structural response of composite horizontal axis wind turbine blades to wind loading is a challenging aeroelastic problem due to the coupling of unsteady aerodynamics and anisotropic structural dynamics. Methods such as Computational Fluid Dynamics (CFD) and Finite Element Analysis (FEA) are readily available through respected commercial software such as ANSYS, but are found to be unsuitable for the preliminary design phase in which many simulations are to be run, due to high computational time. A more efficient algorithm has been developed using a panel method for determining the unsteady aerodynamic blade loading, an anisotropic beam dynamics solver based on the Variational Asymptotic Beam Section (VABS) analysis tool developed by Khouli (2009) and the Ritz method, and the Blade Element Momentum Theory (BEMT).The algorithm was implemented in MATLAB and validated by comparing the results with coupled two-way Fluid-Structure Interaction (FSI) simulations performed using ANSYS Workbench 14. Strong agreement was found between the algorithm results and the corresponding ANSYS simulations. Impressively, the algorithm achieved computational times of less than 2% of the ANSYS simulations. The algorithm is considered a success and has been found to be suitable for use in the preliminary design phase of horizontal axis wind turbines and other flexible, lightweight structures.ii Acknowledgments I would like to thank my thesis co-supervisors: Professors Robert (The Eagle) G.Langlois, master of peer-reviewing, and Fred. F. Afagh, the king of troubleshooting, for their excellent support during this project. I would also like to thank my colleague, Mohamed El Sherif, who always supplied motivating tunes and helped us retain our sanity during the CFD simulations.iii

Development of Computational and Experimental Benchmark Data for Wind Turbine Aeroelastic Algorithms

“…To this end, an algorithm called Preliminary Aeroelastic Analysis of Wind Turbines (PAAC-WTB), developed by McFarlane [1,2], was selected for the purpose of this thesis.…”

“…The PAAC-WTB algorithm models the aerodynamic, structural and dynamic behaviour of any rotor blade to determine its aerodynamic performance and aeroelastic response. The aerodynamic portion of the algorithm uses the 2D Panel Method for the Blade Element Momentum Theory (BEMT) and is developed by McFarlane [2]. It determines the aerodynamic parameters and performance of the blade and consequently the rotor.…”

“…In turn, the structural portion of the program integrates a kinematic beam solver which uses the Variational Asymptotic Beam Section (VABS) analysis developed by Khouli [1] to determine the blade's cross-sectional properties. Finally, using the Ritz method, a kinematic solver is developed to determine the blade's dynamic response to the air flow [2]. It should be noted that in the following chapters of this thesis, any reference to a wind turbine is meant to indicate a horizontal axis wind turbine (HAWT).…”

“…Table 4.3 shows the simulation parameters. Lift coefficient results obtained were then compared to the results obtained from the 2D Unsteady Panel Method used in the PAAC-WTB algorithm [2].…”

“…The second set of analyses were motions that were based on Theodorsen's unsteady model [2,26]. The purpose of Theodorsen's time-dependent solution is to provide a magnitude and phase change to the aerodynamic loading, that is harmonic in nature [25,27].…”