MDO Architectures for Coupled Aerodynamic and Structural Optimization of a Flexible Wing

Abstract

This paper deals with the formulation and testing of different variants of some existing single level generic architectures, specifically for coupled aerodynamic and structural optimization of wing, focused on static aeroelasticity. The design problem involves simultaneous optimization of the wing aerodynamic plan-form and section variables along with its structural sizing variables for minimum load carrying structural weight subjected to structural, aerodynamic, performance and geometric constraints. The associated MultiDisciplinary Analysis (MDA) problem essentially involves coupled solution of the state equations of the aerodynamic and the structural disciplines by nested iterations. The Multidisciplinary Design Optimization (MDO) problem is posed as a three discipline coupled problem, with the trim (maneuver) process required to define structural design loads considered as a separate discipline. This leads to a number of interesting reformulations of the MDO problem based on (i) the reordering of the nested iterations and (ii) decoupling the nested iterations at different levels through the introduction of pseudo design variables and pseudo constraints. Formulation of six variants of the MDO problem and their implementation is presented along with computational issues related to convergence of the iterative processes. A special constraint based on a divergence control parameter has been formulated to handle instability. Optimization results from the different formulations are compared to study their computational performance and bring out the impact of aeroelasticity on the design of the flexible wing.