The standard airframe industry tool for flutter analysis is based
on linear potential predictions of the aerodynamics. Despite the
limitations of the modelling this is even true in the transonic
range. There has been a heavy research effort in the past decade to
use CFD to generate the aerodynamics for flutter simulations, to
improve the reliability of predictions and thereby reduce the risk
and cost of flight testing. The first part of the talk will describe
efforts at Glasgow to couple CFD with structural codes to produce
a time domain simulation and an example calculation will be described for
the BAE SYSTEMS Hawk aircraft.
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A drawback with time domain simulations is that unsteady CFD is still
costly and parametric searches to determine stability through the
growth or decay of responses can quickly become impractical. This has
motivated another active research effort in developing ways of
encapsulating the CFD level aerodynamic predictions in models which
are more affordable for routine application. A number of these
approaches are being developed (eg POD, system identification...)
but none have as yet reached maturity. At Glasgow effort has been
put into developing a method based on the behaviour of the
eigenspectrum of the discrete operator Jacobian, using Hopf
Bifurcation conditions to formulate an augmented system of
steady state equations which can be used to calculate flutter speeds
directly. The talk will give the first three dimensional example
of such a calculation.
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For background reports on these topics see
http://www.aero.gla.ac.uk/Research/CFD/projects/aeroelastics/pubs/menu…