22nd Congress of International Council of the Aeronautical Sciences, Harrogate, UK, 28 August - 1st September, 2000
Paper ICAS 2000-4.7.2

OPTIMIZATION OF TAPERED WING STRUCTURES WITH AEROELASTIC CONSTRAINTS

H. Djojodihardjo, I. W. Tjatra, I. Harjanto
Institute of Technology Bandung , Jl. Ganesha 10 , Bandung 40132 , Indonesia

Keywords: optimization, tapered wing structures, aeroelastic constraints

A methodology for including maximum flutter speed requirement in the preliminary structural wing design is developed. The problem of minimizing structural weight while satisfying static strength, dynamic characteristic and aeroelastic behavioural constraints is stated in a non-linear mathematical form , with beam width and thickness taken as design variables , and solved using gradient-based optimisation technique. Dynamic characteristics of the structure are calculated using finite element model. Laplace form of the unsteady aerodynamics forces are obtained from Fourier transform of unit pulse aerodynamics response. The frequency-domain p-k method is applied for the calculation of aeroelastic stability boundaries. Based upon constraint values and the required gradients, a first order Taylor series approximation is used to develop an approximation linear programming for weight minimization. A modified feasible direction method is, then, applied iteratively to solve the optimisation problem. Validation of the method are carried out in the design of cantilever straight wing structure with 6% hyperbolic airfoil. It will be shown that the optimised wing design can significantly differ from those obtained without optimisation process.

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