Comparison of Two Types of Structural Optimization Procedures for Flutter Requirements

A comparison is made of results obtained from mathematical programing and optimality criteria procedures for the minimum-mass design of typical aircraft wing structures to satisfy prescribed flutter requirements. The mathematical programing method is based on an interior penalty function approach. A Langrangian optimality criterion and an intuitive optimality criterion based on uniform strain energy density are considered. An intuitive resizing procedure is used for both optimality criterion solutions. All results are calculated using the same computer program, changing only the optimization procedure. Both high- and low-aspect-ratio wings are examined. Finite elements are used for structural modeling, and the generalized coordinates for the flutter solution are based on the natural vibration modes of the structure. Second-order piston theory aerodynamics is used for supersonic conditions and kernel function aerodynamics for subsonic conditions. Convergence of the optimality criteria procedures with respect to the number of natural modes is considered. [A ] [B] [Bti] Nomenclature