Equivalent Area Targets for Inverse Design Optimization with Changing Low-Boom Cruise Conditions

Abstract

This paper provides theoretical and numerical justifications for inverse design optimization of reversed equivalent area of low-boom supersonic aircraft when the cruise condition changes during optimization iterations. A modified linear theory for steady flow around a supersonic projectile is used to establish the accuracy of body-of-revolution approximation of a low-boom supersonic aircraft for undertrack sonic-boom analysis using computational fluid dynamics off-body pressure. As a result, designing a low-boom shape of the off-body pressure at three body lengths below the aircraft is equivalent to designing a low-boom shape. A Bezier curve with eight control points is used to define an target for inverse design optimization of of a supersonic aircraft. To make an target matchable by a low-boom supersonic aircraft, the target must have the minimal perceived level of decibels (PLdB) for sonic boom and satisfy two constraints defined by the cruise condition, effective length, and two nondimensional parameters. Numerical results are used to verify that, for different cruise conditions, all optimized targets with PLdB below 70 can be approximately generated by scaling one of them if the targets have the same nondimensional parameters and approximately the same effective length.