Central Queensland University: Spoiler Design and CFD Analysis Report

This report presents a comprehensive analysis of seven different spoiler designs for an SAE formula car, focusing on their aerodynamic performance using Computational Fluid Dynamics (CFD) simulations in Solidworks. The study aimed to optimize the spoiler designs for side drag reduction and improved downforce. The designs underwent iterative modifications, including changes to flap angles, the addition and removal of gurney flaps, and variations in side plate configurations. The simulations assessed the designs based on side drag, downward force, and normal drag. The results indicated that the design iteration 3, featuring cut side plates, demonstrated the best performance, producing significant downforce with minimal drag. The report provides detailed descriptions of each design iteration, along with graphical representations of the simulation results, including velocity and pressure plots. The findings highlight the importance of design choices in achieving optimal aerodynamic characteristics for the spoiler.

7 Different designs of spoiler are prepared and flow analysis is performed. Each designs is named
with with iteration. Details of change of design in each iteration and corresponding design are
discussed here.
Baseline-design – This is run on the basic design of the spoiler with gurney flap.
Iteration 1 – The angle of front flap and gurney flap from air flow direction is reduced by 5 degress
as shown in figure 1.
Iteration 2 – The angle of front flap and gurney flap from air flow direction is increased by 5
degress as shown in figure 2.
Iteration 3 – The side plates are cut to provide space for air vent with existing main flap and gurney
flap as shown in figure 3.
Iteration 4 – The side plates with cuts are opened further in front to allow more air inside the flaps
to increase downforce as shown in figure 4.
Iteration 5 – The side plates are provide with increased cut compared to iteration 3 to increase the
drag further without the extra opening on the side plates as shown in figure 5.
Iteration 6 – The gurney flap is remove from design of iteration 5 as shown in figure 6.
Iteration 7 – The main flap in the iteration 6 is rotated by 12.5 degrees to expose more projected
area to incoming air as shown in figure 7.
All the designs are assessed for side drag (x-direction), down-ward force (y-direction), and normal
drag (z-direction) through flow simulation in Solidworks.
Aims and Objectives
The topic of this thesis is “3D Modelling of SAE formula car rear wing to investigate the side drag
using CFD approach.”
This project aims at:
1. Design a 3D model of rear wing in accordance of SAE.
2. Optimize the wing for better performance using CFD analysis.
3. Optimize the wing to tackle side wind using CFD analysis.
4. Compare and analyse the data and validate using the available data in the literature.
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Figure 1. Design of Spoiler in iteration 1
Figure 2. Design of Spoiler in iteration 2
Figure 3. Design of Spoiler in iteration 3
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Figure 4. Design of Spoiler in iteration 4
Figure 5. Design of Spoiler in iteration 5
Figure 6. Design of Spoiler in iteration 6
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Figure 7. Design of Spoiler in iteration 7
Solidworks 2018 was used to perform the flow simulation on 7 different designs of spoiler. To
perform the flow simulation, one important consideration is to have a bounding box for the part
which should be big enough so that the adjacent wall effect should not affect the flow inside the
part. The flow is modeled as a mix of laminar as well as turbulent. The Goal assignment on overall
part is used to assess the normal drag, downward force and side drag onto the part. Along with this,
the surfaces facing inward air flow is also selected to calculate same values over the course of the
simulations. Gravity is marked ON in the simulation, and simulation is performed as a trasient
study. The air is available as a standard gas material inside Solidworks. Though material assignment
for Spoiler is not important specifically inside flow simulation as it is only used to identify solid
element inside the flow domain. The meshing technique is default inside the domain.
The obtained results for all the 7 designs are assessed through flow simulation and obtained results
are compared subsequently.
The resultant side drag, downward force and normal drag are listed in the table below.
Type of
force Unit Iterati
on 7
Iterati
on 6
Iterati
on 5
Iterati
on 4
Iterati
on 3
Iterati
on 2
Iterati
on 1
Baseline
geometry
X Side Drag
Force (N) [N] -0.078 -0.149 0.138 0.498 0.119 -1.044 -0.014 0.515
Y Downward
Force (N) [N] -322.1 -242.4 -409.1 -349.4 -420.8 -415.0 -398.9 -406.3
Z Drag force
(N) [N] 197.6 131.1 209.9 227.2 211.8 252.4 175.2 209.7
The design of iteration 3 seems to be the best as per the resultant downward force and drag force.
The side drag force is calculated to be almost negligible for all the cases. In iteration 3, the side
plates are cut and space is created so that the incoming air came escape. This is helping to retain the
downward force but at the same time, reduce the normal drag.
4

In iteration 4 design, using the design of iteration 3, the side plates were given a tapered opening to
allow more air to come in but it rather reduced the downward force by the spoiler and increased the
drag. Hence increasing the opening at front of spoiler is not useful.
To further take benefit of cuts on side plates of spoiler in iteration 5, using design of iteration 3,
additional space was cut at the bottom most location. Though as per simulation results, it did not
benefit at all. Most of the air contours are guided by the main front flap and cut at the bottom does
not add much value.
In iteraton 6, the gurney flap from design of iteration 5 was removed. Rationale behind this iteration
was to reduce the drag caused by gurney flap but at minimal cost of down-ward force. Surprisingly,
as the results indicate, both downward force as well as drag reduce significantly hence this design
change was also not successful and not recommended.
In iteration 7, last attempt was made to increase the exposed area of main flap to incoming air so
that the downward force can be increased which will happen at the cost of bit higher drag as well.
As the simulation results indicate, both the components increase but still this design is not better
than iteration 3.
From all the results, it is evident that design made in iteration 3 is by far the best design of spoiler
which will be acoustically also comfortable since bigger passage to outgoing air will produce less
noise. The design is predicted to produce a downward force of ~421 N and normal drag of ~212 N
while side drag is almost negligible. This assessment is done for inlet velocity of 30 m/sec at an
angle of attack of 6 degrees.
Figure 8. Calculated Side drag, down-ward force, and side drag on spoiler as calculated in baseline
design of spoiler with gurney flap
5

Figure 9. Iso-vector plot of velocity for air-flow across spoiler for baseline geometry
Figure 10. Decrease of area exposed by rotating the main flap and gurney flap by rotating anti-
clockwise for iteration 1
Figure 11. Increase of area exposed by rotating the main flap and gurney flap by rotating clockwise
for iteration 2
6

Figure 12. Air flow vectors representing pressure across spoiler with design as described for
iteration 1
7

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Figure 13. Flow simulation results from all the iterations as obtained from Solidworks
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Figure 14. Velocity Cut plot on Spoiler design (iteration 3) as obtained after flow simulation in
Solidworks
Figure 15. Pressure Cut plot on Spoiler design (iteration 3) as obtained after flow simulation in
Solidworks
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Figure 16. Pressure Surface plot on Spoiler design (iteration 3) as obtained after flow simulation in
Solidworks
Figure 17. Wind flow diagram across spoiler (iteration 3) showing velocity values and air vectors as
directed by spoiler
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Figure 18. Dimensional sketch of Spoiler (Iteration 3)
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