Adaptive Aft Signature Shaping of a Low-Boom Supersonic Aircraft Using Off-Body Pressures

Abstract

The design and optimization of a low-boom supersonic aircraft using the state-of-theart off-body aerodynamics and sonic boom analysis has long been a challenging problem. The focus of this paper is to demonstrate an effective geometry parameterization scheme and a numerical optimization approach for the aft shaping of a low-boom supersonic aircraft using off-body pressure calculations. A gradient-based numerical optimization algorithm that models the objective and constraints as response surface equations is used to drive the aft ground signature toward a ramp shape. The design objective is the minimization of the variation between the ground signature and the target signature subject to several geometric and signature constraints. The target signature is computed by using a least-squares regression of the aft portion of the ground signature. The parameterization and the deformation of the geometry is performed with a NASA inhouse shaping tool. The optimization algorithm uses the shaping tool to drive the geometric deformation of a horizontal tail with a parameterization scheme that consists of seven camber design variables and an additional design variable that describes the spanwise location of the midspan section. The demonstration cases show that numerical optimization using the state-of-the-art off-body aerodynamic calculations is not only feasible and repeatable but also allows the exploration of complex design spaces for which a knowledge-based design method becomes less effective. Nomenclature Acronyms BOSS= boom optimization using smoothest shape (a computer code for low-boom design) CFD = computational fluid dynamics DFO = derivative-free optimization DOE = design of experiments GBO = gradient-based optimization PLdB = perceived loudness in decibels psf = pounds per square foot Symbols C L = coefficient of lift dp/p = near-field pressure waveform X e = equivalent length

A Method for Reducing Sonic Boom Strength by Tailoring the Shape of the Propulsive Streamtube

“…1,2 The magnitude of the combined pressure disturbances depends directly on the amount of flow deflected away from the nacelle and the physical process through which the deflection occurs. The more flow requiring deflection, and the shorter the spatial distance over which the deflection must occur, the stronger the compression features produced by the nacelle's surface and the streamtube at either end of it.…”

Rapid Parameterization Schemes for Aircraft Shape Optimization

“…The final optimized horizontal tail of the low-boom optimization result (also see ref. [14]) is shown in Figs. 9 and 10.…”

“…Figures 9 and 10 illustrate a parametric scheme for modifying the camber surface of a horizontal tail. This parametric scheme was used to improve the aft signature of a low-boom supersonic demonstrator [14]. Among the nine control points that are shown in Fig.…”

Advanced Usage of Vehicle Sketch Pad for CFD-Based Conceptual Design

“…The difficulty for the fuselage volume shaping is the determination of a parameterization scheme for the fuselage area distribution that will yield the required distribution for a low-boom configuration. Instead of using a trial-and-error method, an effective method of using smoothest shape modifications (called BOSS) with a high number (e.g., over 120) of design variables can be used to obtain the least oscillatory fuselage shape that yields a low-boom configuration [6,12]. Figures 5 and 6 show the reversed equivalent area distributions and the corresponding ground signatures for the baseline and the final design.…”

“…A horizontal tail lift tailoring optimization was demonstrated with PROTEUS by Ordaz and Li [12] for the configuration shown in Fig. 7.…”