UWE Bristol Engineering showcase 2015

Morgan Harmer
MEng Design Aerospace Engineering
Project Supervisor
Dr. Chris Toomer
Project Given by MBDA
Vortex Switching
Project Outline
Many simulations were run successfully, offering insight into the formation of
symmetrical vortices. Although simulations were run at supersonic speeds, it was found
that Mach number had little effect on the type of vortex generated. Increased speed
was found only to have the effect of stretching the vortex longitudinally.
Simulations were run with two different incidence angles, α=10° and α=40°. The α=10°
results were found not to fully generate vortices. However a ‘vortex bubble’ did appear
under inspection. This vortex bubble is shown below at Mach 2.
Right
This image shows the vortex core
region generated around a 3 calibre
long tangent ogive at Mach 2 with an
incidence angle of 40°.
Introduction
A large amount of research has gone into the design and
production of so called “Super Agile” missiles. These “Super
agile” missiles allow a military aircraft to target threats within a
much larger scope than the traditional air-to-air missile. This
results in missiles being required to regularly experience
excessive angles of attack. When a missile is operating at a large
angle of attack (i.e. over 10°) one or more vortices may attach
from the nose along the port or starboard side. Depending on
how the vortices attach, the missile can experience an
unpredictable variety of pitch, roll and yaw moments. The
sketch left demonstrates the formation of asymmetric vortex
shedding as a result of a high angle of attack.
Project summary
This Project aimed to understand the
behaviour of asymmetrical vortex shedding
from the nose of a slender body such as a
missile at medium to high incidence.
Project Objectives
The main objective of this investigation was
to answer the question; once asymmetrical
vortices have developed with one side more
dominant than the other, can they switch?
Project Conclusion
The experiments proved inconclusive. Only
symmetrical vortices developed, and were
found to be stable.
From reading articles and technical reports,
others have found that asymmetrical vortices
at the nose, like symmetrical ones, are stable.
From the same sources, it was found that if a
critical roll angle was reached, the vortices
may switch.
Next years work will further investigate this
area.