Aeroelastic Issues in Multidisciplinary Design Optimization of Aircraft Configurations

This paper presents recent work to address aeroelastic constraints effects on the multidisciplinary design optimization for conceptual design (MDO-CD) of civil transportation aircraft. Specifically, the formulation developed by the authors is applied to find the optimal design of an aircraft characterized by a low environmental impact. Different objective functions are taken into account. Specifically the wing structural weight, the fuel burn, the total aircraft life-cycle cost and the noise emissions are taken as the functions to minimize during the optimization process. In order to address the effects of the aeroelastic constraints on the final optimal solutions, two different feasible subspace (defined by different values of the minimum flutter/divergence speed) are taken into account. The optimization process is here applied to an extended range narrow body aircraft with over the wing mounted engines. Within the MDO-CD framework used here, the analysis modules are, whenever possible, prime-principle based. Specifically, the structural problem is solved using a finite element method (FEM), the aerodynamics is evaluated through a quasi-potential formulation for compressible flows, enriched by a boundary-layer integral model to take into account the effects of viscosity and to provide an adequate estimation of viscous drag, whereas the aeroelastic analysis is performed by using a reduced-order model based on a finite-state approximation. The aeroacoustics is evaluated through well-assessed and efficient empirical or semi-empirical models which can provide the estimation of the noise level. The optimization procedure is conducted using a genetic algorithm coupled with a penalty function method.