Integrating analytical aeroelastic instability analysis into design optimization of aircraft wing structures

Abstract

Two analytical flutter solution approaches have been developed to optimize two and three dimensional aircraft wing structures with design criteria based on aeroelastic instabilities. The first approach uses open loop structural dynamics and stability analysis for a two dimensional wing model in order to obtain the critical speeds of flutter, divergence and control reversal for optimization process. The second approach involves a flutter solution for three dimensional wing structures by using assumed mode technique and is applied to aeroelastic optimization based on flutter criterion efficiently. This flutter solution employs energy equations and Theodorsen function for aerodynamic load calculation and is fully-parametric in terms of design variables which are taper ratio, sweep angle, elasticity and shear modulus. Since bending and torsional natural frequencies are required for flutter solution, a free vibration analysis of aircraft wing is developed analytically as well. The analytical results obtained for flutter solution of AGARD 445.6 wing model for Mach number of 0.9011 are found to be compliant with the experimental results from literature. Next, the three dimensional flutter code is coupled with optimization framework to perform flutter based optimization of AGARD 445.6 to maximize the flutter speed.