Document Type : Original Article
Associate Professor, National Research Centre, Dokki, Cairo, Egypt.
Professor, Aerospace Engineering, Faculty of Engineering, Cairo University, Giza, Egypt.
Egyptian Armed Forces, Egypt.
This paper presents a coupled aerodynamic/structural optimization model for a light training, low subsonic aircraft wing. Four optimization strategies have been developed and tested. The first was based on minimization of the total weight of the main wing structure subject to strength, stiffness and aeroelastic constraints. The second strategy considered maximization of the critical flight speed at which divergence occurs, while the third one focused on minimization of the wing drag/lift ratio as a measure of improving aerodynamic efficiency without violating structural weight requirements. The last strategy was based on minimization of the power consumption, which has worked very well and shown balanced improvements in both the aerodynamic and structural efficiencies of the wing under the imposed design constraints. The aerodynamic variables are chosen to be the wing aspect and chord taper ratios, while the structural variables encompassed spar locations, spar flange cross-sectional areas, shear webs and covering skin thicknesses of the main wing box section. The optimization problem has been formulated as a nonlinear mathematical programming problem solved by invoking the MATLab optimization Toolbox routines, which implements the method of feasible directions. Structural, aerodynamic and aeroelastic analyses assumed slender one-dimensional configuration. It makes use of the quasi-steady strip theory in evaluating aerodynamic loads and the classical engineering theories of bending and torsion in calculating stresses and deformations. Results have shown that the approach implemented in
this study can be efficient in producing improved designs in a reasonable computer time. The proposed model has succeeded in arriving at the optimum solutions showing significant improvements in the needed design goals as compared with a baseline wing design.