this is what the article concludes that we do require changes in the design of the fuselage if we change the design of the air intakes but no where in the article suggest that there is a change necessary required in the exhaust if there is any change in the design of the air intake.
Air intakes are necessary for all vehicles propelled by airbreathing
means, whether they be aircraft, missiles,
helicopters or, in the future, reusable space launchers.
They will directly condition the propulsive performance
(thrust, drag, weight, thermal properties, lift) of the
vehicles in which they are mounted. They are subject to a
multitude of constraints (Mach number, angle of attack
and yaw angle, possible injections, discretion, engine
failure, among others).
The first step in air intake design is thus to "clearly
identify all of the air intake's specifications".
After a short phase in which the air intake is defined alone
comes the phase in which the external aerodynamic field is
effectively considered with its over- and under-speeds,
vortices, boundary layers, transverse gradients, nose and
other effects.
The second step is thus to "find the best location for the
air intake(s) and, if possible, modify the upstream part
of the fuselage to improve the captured air flow".
Air intakes have very complex internal flows, including
sub-, trans-, and supersonic zones simultaneously. There
are many interactions (shock/shock, shock/boundary layer,
vortex/wall, corner effect) and they are generally
combined. Many non-steady aspects are to be considered,
and notably the buzz which is critical for structural
dimensioning and operating limits. The air intake's
matching with the engine that it supplies must always be
ensured.
The third step is then to "carry out some calculations,
but use essentially previous experience (bibliography,
personal knowledge) and wind tunnel tests at high
Reynolds numbers".
Air intakes must be designed by a "System" approach.
Optimising them is a long and difficult process.
