Artificial neural network-based meta-models for predicting the aerodynamic characteristics of two-dimensional airfoils for small horizontal axis wind turbine

Abstract

Blade element momentum theory is extensively used to design and characterize the performance of the wind turbine. Aerodynamic characteristics of the airfoils used in the blades of the wind turbine are one of the crucial parameters of the blade element momentum theory. The aerodynamic characteristics of airfoil can be significantly influenced by Reynolds number besides the angle of attack. Thus, an inadequate consideration of Reynolds number for aerodynamic characteristics of the airfoil can result in discrepancy in the optimum design and performance evaluation capability of the blade element momentum theory. Several mathematical models, and semi-empirical relations to parameterize the aerodynamic characteristics of two-dimensional airfoil in blade element momentum theory, inherently lack dependency on Reynolds number and thus open a scope for uncertainty. An artificial neural network-based model is proposed to predict the lift and drag coefficient of airfoil as a function of not only the angle of attack but also the Reynolds number. A series of six in-house developed airfoils for small wind turbine have been considered for the present study. The computational fluid dynamic results of the airfoil with a range of Reynolds number (100,000–2,000,000) and angle of attack (0°–20°) were utilized to develop the model. A high coefficient of determination and low root-mean-square error of the developed models for a test dataset suggests the robust capabilities and effective topology of the artificial neural network-based model to predict the lift and drag coefficient of the airfoils with respect to a given angle of attack and Reynolds number. The developed model can then be used to replace the traditional analytical or semi-empirical model for mathematical representation of airfoil in the blade element momentum theory and thus reduce the uncertainty on account of inadequate consideration of Reynolds number for aerodynamic characteristics of airfoil in design and performance evaluation.