It
has been shown that counter-rotating structures (Görtler vortices)
form in the vortex/surface interaction region over a delta wing at angle
of attack. These structures convect around the primary vortex in a helical
fashion, causing nearly periodic velocity fluctuations in the flowfield.
A centrifugal instability is hypothesized as the driving mechanism for
the generation of the structures which form with a preferred frequency
as a function of velocity and angle of attack. The figure shows a
summary of the results obtained by Hubner. Through the past research by
Hubner and this present research, many questions have been answered regarding
the origin of the fluctuations, but there are also many unanswered questions
and new questions that need further research to answer. Specifically, what
is the mechanism that selects the dominant peak frequency and generates
the frequency characteristics seen in experiments? Can experimentally investigating
the centrifugal instability mechanism offer insight into this, such that
a frequency prediction tool can be developed? Can the results of this investigation
be applied to an actual fighter aircraft to reduce tail buffeting? These
questions are to be answered by the future research.