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

Abstract

This paper introduces a tool for boom optimization using smoothest shape modifications. This tool allows interactive inverse design optimization to develop a fuselage shape that yields a low-boom aircraft configuration. A fundamental reason for developing this boom optimization tool is the need to generate feasible low-boom conceptual designs that are appropriate for further refinement using computational-fluid-dynamics-based preliminary design methods. The boom optimization tool was not developed to provide a numerical solution to the inverse design problem. Instead, it was intended to help designers find the right configuration among an infinite number of possible configurations that are equally good using any numerical figure of merit This boom optimization tool uses the smoothest shape modification strategy for modifying the fuselage radius distribution at 100 or more longitudinal locations to find a smooth fuselage shape, which reduces the discrepancies between the design and target equivalent area distributions over any specified range of effective distance. For any given supersonic concept (with wing, fuselage, nacelles, tails, and/or canards), a designer can examine the differences between the design and target equivalent areas, decide which part of the design equivalent area curve needs to be modified, choose a desirable rate for the reduction of the discrepancies over the specified range, and select a parameter for smoothness control of the fuselage shape. The boom optimization tool will then generate a fuselage shape based on the designer's inputs in a matter of seconds. Using this tool, within a few hours, a designer can either generate a realistic fuselage shape that yields a supersonic configuration with a low-boom ground signature or quickly eliminate any configuration that cannot achieve low-boom characteristics with fuselage shaping alone. A conceptual design case study is documented to demonstrate how this boom optimization tool can be used to develop a low-boom supersonic concept from a low-drag supersonic concept The paper also contains a study on how perturbations in the equivalent area distribution affect the ground signature shape and how new target area distributions for low-boom signatures can be constructed using superposition of equivalent area distributions derived from the Seebass-George-Darden theory.