Using CFD Surface Solutions to Shape Sonic Boom Signatures Propagated from Off-Body Pressure

Abstract

The conceptual design of a low-boom and low-drag supersonic aircraft remains a challenge despite significant progress in recent years. Inverse design using reversed equivalent area and adjoint methods have been demonstrated to be effective in shaping the ground signature propagated from computational fluid dynamics (CFD) off-body pressure distributions. However, there is still a need to reduce the computational cost in the early stages of design to obtain a baseline that is feasible for low-boom shaping, and in the search for a robust low-boom design over the entire sonic boom footprint. The proposed design method addresses the need to reduce the computational cost for robust low-boom design by using surface pressure distributions from CFD solutions to shape sonic boom ground signatures propagated from CFD off-body pressure. Nomenclature Acronyms BOSS= boom optimization using smoothest shape (a computer code for low-boom design) CFD = computational fluid dynamics SymbolsA e = equivalent area A Mach e,baseline = classical equivalent area based on Mach tangent cutting planes for the baseline configuration A Mach e,design = classical equivalent area based on Mach tangent cutting planes for the design configuration A e,mixed = reversed equivalent area prediction for the design configuration A reversed e,baseline = reversed equivalent area for the design configuration dp/p = off-body pressure distribution

Conceptual Design of Low-Boom Aircraft with Flight Trim Requirement

“…IV). The analysis codes described are integrated into a ModelCenter [8] model that allows early conceptual design and layout of a configuration using the mixed-fidelity A e approach described in [9].…”

“…The trim-feasible target formulation is based on the mixed-fidelity A e design approach described in [9]. The design methodology shows that the sensitivity of A rev e to design changes can be approximated by the sensitivity of A Mach e , which is based on a surface pressure distribution [see Eq.…”

“…If the change in target A e is assumed to be mainly a result of changes in A lift e , as shown by the mixed-fidelity approach described in [9], then this change in lift distribution manifests itself as 1) an increase in target A e fore of the x e location of cg x , 2) a decrease or flattening of the target A e aft of the x e location of cg x , or 3) a combination of the two scenarios. If the end value of the target A e is fixed, then this can drive the target A e toward a design space region that is less amenable to low boom.…”

“…The baseline configuration is now shaped using the mixed-fidelity A e approach described in [9]. A parametric scheme based on camber deformation is placed on the main wing, with the camber design variable locations shown in Fig.…”

Feasibility of Supersonic Aircraft Concepts for Low-Boom and Flight Trim Constraints

“…References after 2010 include validation of CFD methods for computing off-body pressure distributions 1-10 by using novel wind tunnel measurement techniques, [11][12][13][14][15][16][17] new methods for design of low-boom supersonic configurations, [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37] and development of low-boom supersonic concepts that include nacelles and some mission constraints. [28][29][30][31][32][33][34][35][36][37][38][39][40][41] One of the remaining technical challenges in development of low-boom supersonic concepts is the difficulty of knowing when to continue work on the current configuration layout for a trimmed low-boom design and when to move on with a more promising concept. It is not unusual to work on a seemingly promising concept for many months, and then realize that it would be impossible to achieve a trimmed low-boom design by only morphing the OML at the given cruise condition.…”