UWE Bristol Engineering showcase 2015

Abbie Grange
MEng Motorsport Engineering
Project Supervisor
Dr Rohitha Weerasinghe
Parametric Analysis and Optimisation of the Formula Student Body Shell
Formation of the Parametric Model
A parametric model maintains consistent
relationships between certain elements, allowing
the model to adapt to changes made to a specific
variable. Parametric modelling is vital to the
research undertaken in this study as it allows the
Author to make structured, predefined changes
that will automatically update the rest of the nose
cone geometry and therefore ensure cohesive,
reliable results.
The body shell as a whole is defined and
constrained around the chassis, with given
clearances at key points that ensure the full
clearance of all components. The nose cone region
specifically is largely constrained to the impact
attenuator as this is the last component that the
body shell must clear before coming to a point.
Utilising the geometry of the impact attenuator
ensures proper fitment and clearance of the body
shell, no matter what changes are made to the
parametric model.
Nose Cone Height Study
This section of the investigation tests the isolated
nose cone region as a lone bluff body which ends
at the front roll hoop, therefore the cockpit region
and the side pods are not included. As has been
noted, the height study is split into categorised
geometry and linear geometry analysis.
Lift (N)
It can be seen that there is a distinct reduction in
the lift generated by the nose cone area when the
nose cone height is increased; however the drag
value remains largely unchanged. What is
significant in the lift comparison chart is the
increased stability of the lift values upon changing
from categorised to linear geometry selection.
Nose Cone Radii Study
The underbody radii study aims to investigate the
impact of changes to the underbody curvature
with a constant optimum nose cone height of
225mm above ground.
Lift (N)
0
-1
-2
-3
-4
-5
-6
-7
-8
-9
-2
-4
-6
-8
-10
-12
-14
Lift Comparison
0 50 100 150 200 250 300 350 400
Nose Cone Height Above Ground (mm)
Underbody Radii Study Lift
0
90 100 110 120 130 140 150 160
Bottom Dimension
y = 0.0159x - 12.555
Categorised
Linear
Further examination of the actual resulting lift
values combined with the addition of a linear
trend line appears to show that, whilst the values
appear almost oscillatory, the magnitudes by
which they change are very small, with a
maximum of 3N between each model.
Lift
Linear (Lift)
Assembly Analysis
Inclusion of the chassis and suspension geometry
is essential if the flow around the body shell is to
be fully understood. Modelling the assembly flow
allows for the interpretation of not only the
aerodynamics of the body shell as a standalone
piece, but also its inherent effects on the flow
around various other important components.
Unfortunately the flow over the upper surface of
the nose cone does not provide sufficient energy
to deflect the flow up and over this feature and
the inclusion of a deflective screen would impair
the drivers’ visibility.
Transient Analysis
Transient analysis involves the simulation of flow
events over a predefined time period as opposed
singular moments in time.
The three second view also shows a secondary
separation bubble beginning to form near the
lower surface of the cockpit. This secondary
bubble grows in magnitude as the speed increases
resulting in two fully formed areas of flow
separation.
Project Summary
This study involves the optimisation of the UWE
Formula Student body shell using a parametric
modelling process. The investigation explores the
effect of nose cone height and surrounding curvature
on the lift and drag values experienced by the vehicle
by conducting analysis using Computational Fluid
Dynamics (CFD) software alongside wind tunnel
testing. Upon discovery of an optimum design, full
transient analysis is undertaken with variable inlet
speeds as well as steady state analysis of the effects
of inclusion of the vehicle assembly.
Project Objectives
• To design and analyse a body shell for the UWE
Formula Student 2014 vehicle using parametric
modelling and analysis.
• To optimise the nose cone height and understand
the effect of change of surrounding surface radii
on lift and drag.
• To undertake transient analysis of the optimum
design.
• To validate computer based testing with wind
tunnel analysis that includes ground effect.
Project Conclusion
As the two separate geometric studies show, lift
characteristics appear to be heavily governed by the
height at which the nose cone sits from the ground as
opposed to the surrounding surface curvature.
Analysis would suggest that changing of the
underbody surface, whilst having some measurable
effect lacks a significant trend line and is therefore
negligible at the speeds tested. It would be
recommended that the Team carefully consider the
nose cone height with a view of optimising it in terms
of negative lift force so as to counteract the inherent
lift generated when the vehicle assembly is added.