Limited aerodynamic improvement potential for a Concorde-like aircraft

When comparing aerodynamic improvements since ihc Concorde’s lime, we find strong differ­ences in the aerodynamic efficiency between Concorde lime subsonic aircraft like B747 or B737 and modern aircraft like the B777. A340or A320. expressed by improved L/D (lift/drag). These subsonic aircraft fly at high subsonic Mach numbers, when the air flow at the aircraft locally reaches panially subsonic, partially supersonic Mach numbers, which ls named transonic flow. Physics of transonic flow include strong nonlmearities like shock waves, and the governing equations change from elliptic to hyperbolic type Whereas the old aircraft were designed using pure subsonic linear potential flow theory combined with simple sweep theory, improvements were provided exploiting nonlinear theory, the latter require modem high performance comput­ers not available for Concorde development

But flow around supersonic airliners like the Concorde is dominated by small distur­bances of the incoming flow, because strong disturbances would create high wave drag There­fore. design of supersonic airliners can mostly be based on linearized potential flow theory, as was the Concorde (slender body theory). Only for some pans nonlinear effects have to be respected for: strong interference effects like engine integration, fine tuning of the configuration and strongly nonlinear boundary layer flows. But. except for laminar flow, other strongly non­linear boundary layer flows like separation arc avoided because they arc connected with large drag increases Therefore, modem nonlinear aerodynamic theory can only provide limited improvements compared to Concorde (except for laminar flow).

Although, some aerodynamic improvements may be provided:

• New materials providing higher specific stiffness may allow a higher aspect ratio via inter­disciplinary effects.

• Local optimization for nonlinear flow phenomena will prov ide reduced interference drag, especially for engine integration.

• Supersonic laminar flow is the only new aerodynamic technology which can strongly improve performance. But it is still far away from realization for large transport aircraft.