A Study On Integrated Aerodynamic/Structural Design Of Joined-Wing Aircraft

Joined-wing configuration features diamond-shapes in both the plan and front views. The front wing is aft swept with positive-dihedral angle and the rear wing is forward swept with negative dihedral angle. As an innovative aircraft configuration, its essence is the integration of aerodynamics and structure. This thesis aims at how to apply multidisciplinary design optimization methods to the integrated aerodynamic/structural design of the joined-wing aircraft.Based on the compatibility constrained optimization and the collaborative optimization, this thesis proposes a two-level optimization approach for integrated aerodynamic/structural design of wings. In this approach, design tasks are decomposed into a system-level optimization and subsystem-level optimizations. The task of each subsystem optimization is to find the local variables to minimize or maximize objectives, subject to its local design constraints. The task of the system-level optimization is to find global (or shared) and auxiliary variables to optimize the system performances, and satisfy the consistency constraints. The consistency constraints provide a way to decouple the disciplines and make the parallel subsystem optimization possible. The surrogate-based two-level optimization is developed by use of the surrogate model in the two-level optimization. The integrated aerodynamic/structural design optimization of a simple general aviation aircraft wing demonstrates that the basic two-level optimization is simple in terms of implementation and stable in terms of computation, while the surrogate-based one has the better ability to find the global optimum. The application of the surrogate-based two-level optimization to the integrated aerodynamic/structural design of joined-wing aircraft resulted in the substantial improvement in terms of flight compared to the initial design.The design processes are accomplished automatically using the general optimization software iSIGHT. The design cycle can be shortened with the aid of the software iSIGHT.