The Aerodynamical Optimal Design with Structure Interactions

Abstract The aerodynamical optimal design (OD) of the shape of flying configurations (FCs) can be improved by refinements of its start software used for the optimization and of the optimization strategy itself. The author has two times enlarged the classical variational method. The first one consists in the inviscid global OD of the FC’s shape (the optimization of the camber, twist, thickness and also of its similarity parameters of the planform) and leads to a variational problem with free boundary. The optimum-optimorum (OO) FC’s shape is chosen in the frame of a class of admissible FCs, defined by some properties. In the second enlargement an iterative OO theory is developed. The inviscid OO-FC’s shape represents now the first step in the iterative viscous shape optimization process. A checking of the inviscid OO-FC’s shape is made with own zonal, spectral solutions for the Navier-Stokes layer (NSL). The inviscid OO-FC’s shape is checked. Additional constraints for thermal, structural or NSL reasons occur. In the second step of optimization, the predicted inviscid OO-FC’s shape is corrected by adding these constraints in the variational problem and of the friction drag coefficient in the drag functional. This weak interaction aerodynamic/ structure, via additional structure constraints in the aerodynamical OD of the FC’s shape, is the new element of this study. The introduction of a central fuselage zone of the wing is useful for the control of the structure thickness in the central part of the wing. The removing of the position of the zero-thickness line outside of the planform of the FC, behind the FC’s trailing edge, can control the thickness magnitude of the FC near the hinge lines of the trailing edge flaps. The moving of the Kutta condition on the FC’s leading edges to a lower Mach number than of cruise, reduces the camber and the twist of the FC. This modified aerodynamical OO-FC’s shape satisfies also the requirements of the structure.