Advanced algorithms for design and optimization of Quiet Supersonic Platforms

Abstract

This paper describes the work carried out within the Stanford University group as part of the DARPA-funded Quiet Supersonic Platform (QSP) project. The objective of our work was to develop advanced numerical methods to facilitate the analysis and design of low sonic boom aircraft. The focus of the boom reduction activities was placed on two main ideas: the shaping of the configuration and a multidisciplinary design approach to minimize its total empty weight. Accurate and efficient tools are needed to achieve these tasks. Our approach was meant to enhance the existing state-of-the-art which was developed in the 1970s and during the early stages of the High Speed Research (HSR) program. For that purpose, we designed tools that would ultimately become fully nonlinear (in contrast with current design efforts based on linear theories of the 1970s). These tools are also able to account for important tradeoffs between boom reduction and aerodynamic perormance, as well as other disciplines. Because of the difficulty of the problem, the tools were designed to support a combination of gradient and non-gradient automatic optimization techniques. As a result of our efforts, rapid turnaround boom analysis and design methods were developed. These methods permit the investigation of radical configuration changes and their effect on the ground boom signature and the L/D ratio of the aircraft. We have also created an environment for the automatic nonlinear analysis of QSP configurations based on the multiblock flow solver FLO107-MB. In addition, we have extended the adjoint-based design method to treat remote sensitivities to near-field pressure signatures, allowing for a very large number of parameters to be used in modifications of the aircraft geometry. All tools were carefully validated against existing experimental data, other boom prediction programs, and with systematic mesh refinement studies.

Integration of Multifidelity Multidisciplinary Computer Codes for Design and Analysis of Supersonic Aircraft

“…[1][2][3][4][5][6][7][8][9][10][11][12][13] There are also many examples of conceptual aircraft design reports where the authors described going "deep" in a particular discipline, focusing on a single cruise point low-boom and/or low-drag design in their process. [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30] Many of these are often byproducts of tool and method development and the testing of optimization algorithms and/or schemes.…”

Aerodynamic Shape Optimization Using First and Second Order Adjoint and Direct Approaches

“…The flow equations are solved over the domain defined between the aircraft and the near field boundary while the flow analysis at the domain between the near field boundary and the ground plane is based on principles of geometrical acoustics and nonlinear wave propagation. The problem of finding the optimal shape that produces desired pressure signature at the ground is addressed in [75].…”

“…[72][73][74][75][76]. The functional can be defined either in a near field boundary, [73,74], or at the ground level.…”

Interactive Inverse Design Optimization of Fuselage Shape for Low-Boom Supersonic Concepts

“…13,31,[34][35][36][37][38][39] An open question is "What objective function could lead to an optimal solution having a shaped boom signature with a low level of loudness?" Various forms of objective functions, including the initial overpressure, perceived loudness, drag, and so on, were proposed.…”