An Exergy Approach for High-Fidelity Analysis and Optimization of Aerospace Systems

The development of next generation aircraft is trending towards more interconnected and highly multidisciplinary systems. To better support the design of these systems, an alternative approach to design is needed beyond traditional methods. An automated design approach by means of multidisciplinary design, analysis, and optimization (MDAO) offers the potential to enable aircraft concepts traditional designers may not have considered. However, the selection of objective function for optimization remains an ambiguous choice by the designer. To remove ambiguity from the choice of objective function, a universal measure of performance in the form of exergy and its destruction can be used. Through the quantity of exergy, typically disparate systems such as the force-based approach of aerodynamics can be compared in a one-to-one fashion to the energetic-based approach of a thermal or propulsion system.In this thesis, a high-fidelity approach for aerodynamic and thermo-mechanical exergy destruction evaluation and sensitivity analysis is provided to enable gradient-based design optimization. To arrive at the exergy destruction equations, a formal development of the entropy balance equation from the concavity property of entropy is presented. From the balance equations, the exergy destruction equations can be derived for arbitrary thermal and fluid processes. The aerodynamic exergy destruction functional is implemented in FUN3D and a rigorous verification effort is conducted demonstrating good functional agreement with test cases. Additionally, the discrete adjoint is implemented and demonstrates discrete agreement with complex-step derivatives. A series of trade studies are then conducted on the Generic Hypersonic Vehicle (GHV) to identify performance metrics of the vehicle. The thermal exergy destruction functional is implemented in MAST along with a series of verification cases for the functional and discrete adjoint demonstrating discrete agreement. A series of thermal exergy destruction trade studies are performed on the GHV and some modeling and design perspectives are discussed. Finally, a series of optimization cases are presented demonstrating the use of exergy destruction as an objective function. A series of inverse design problems are conducted as well as inviscid aerodynamic exergy destruction optimizations of the GHV. These contributions demonstrate the utility of the exergy quantity as a universal measure of performance and push the state of the art in the area of exergy-based analysis and optimization.