Eventos Anais de eventos
COBEM 2021
26th International Congress of Mechanical Engineering
Analysis of the structural characteristics of 4- and 5-digit NACA airfoils from a MDO perspective
Submission Author:
Murilo Sartorato , SP , Brazil
Co-Authors:
Lucas Silva Viotto, Murilo Sartorato
Presenter: Murilo Sartorato
doi://10.26678/ABCM.COBEM2021.COB2021-0381
Abstract
The present work proposes to comparatively analyze the influence of thickness and curvature of airfoils on the structural parameters and weight of wing sections, comparing the changes on aerodynamic efficiency these changes bring to the structural efficiency of an optimal wing section of a given airfoil shape. For that, different families of 4- and 5-digit NACA airfoil are used as the basic shape for the torque box of semi-monocoque metallic wing structures; then these wing structures weights are optimized by varying the number and shape of stringers, using predetermined T, Z, J, and hat cross sections, and the thickness of each panel, bounded by the maximum buckling stresses for that geometry, using a genetic-algorithm pre-implemented within Python libraries. The stresses are taken from the bending and shear of the wing structure and are calculated using a classic analytical model, automated in Python language, for asymmetric bending and shear flow in thin reinforced closed beams based on the aerodynamic and inertial loads calculated for each airfoil using XFOIL. Although the aerodynamic efficiency is linked to the thickness and curvature of the airfoils, this analysis aims to compare the influence of the aerodynamic efficiency gain on the weight, since the change of airfoil directly influences the position of the shear center and the distribution of bending shear loads, which can lead to a neutral or even negative net gain in drag/weight ratio. First, results regarding the impact of different genetic algorithm parameters and models such as mutation, crossover, and elitism ratio over the convergence of the model are shown. Finally, an analysis of the influence of thickness and curvature of the airfoils through comparing the results for the different members of the chosen NACA families by comparing different aerodynamic metrics such as efficiency, max lift coefficient, and performance metrics to the structural efficiency metrics of the optimized structure like weight, number of stringers, maximum stresses, and overall safety margins.
Keywords
Optimization, genetic algorithm, wing structures, MDO
