UWE Bristol Engineering showcase 2015

Marco Otero
MEng Motorsport Engineering
Project Supervisor
Dr Yufeng Yao
Drag reduction system development for heavy goods vehicles
Reference Vehicle
Gap Devices
The device used to improve the gap region was to use a
splitter. The aim of the splitter was to prevent flow
interacting across the entirety of the region, stopping a
large wake occurring in the gap. This would reduce the
wake size, causing two smaller wakes either side of it.
The length of the splitter was changed, as was the side
of the gap it was located.
Drag
Count
Drop
50
45
40
35
30
25
20
15
10
5
0
Comparison between best design iterations
Tail Splitter tapered trailer Gap Splitter Underside
Skirting
Underside
Profiling
The reference vehicle used was based on a Volvo tractor with a
standard trailer. Through the use of CFD the drag coefficient of the
vehicle was found to be 0.8. There were three regions on the reference
vehicle highlighted for improvement; the tractor trailer gap, underside
of the vehicle and at the rear of the trailer. These are highlighted on
side velocity contour by the low speed flow in blue. These regions
produced that largest amounts of wake, with an especially large wake
occurring behind the tail face of the vehicle.
Drag
Count
Drop
Tail Edge Devices
Two devices were used to improve the flow at the
rear of the vehicle; splitters and a tapered device.
These aimed to prevent the large wake occurring
behind the vehicle by reducing the interaction in the
region. The splitters had their location and length
changed, whilst the tapered device changed in
length and tapering angle.
Results
A tail end tapered device produced the best result
with a drag count reduction of 49. this reduced the
drag coefficient of the vehicle from 0.800 down to
0.751. When projecting this device for a year in use,
it was found that 113 litres of fuel could be saved
when applying an average mileage of 80’000.
Devices for the underside of the vehicle were not
very effective despite attempts to optimize,
however, their performance is expected to improve
when under crosswind conditions.
Underside Devices
Side skirtings were the device used to improve the
airflow underneath the vehicle. The aim of the
skirtings were to prevent the low velocity flow under
the vehicle from interacting with the high velocity
free stream flow to the sides of the trailer. The
skirtings varied in length and height in an attempt to
optimize the design.
Pressure
(Pa)
Tail Face Pressure Comparison
150
120
90
60
30
0
-9 -6 -3 0 3 6 9
Distance from Centreline (m)
Reference (Pa)
Tapered (Pa)
Project summary
An investigation has been conducted to design and
develop drag reduction systems for a heavy goods
vehicle with the aim of reducing the fuel consumption
by reducing the drag coefficient.
The designs were attached to a reference vehicle and
analyzed through CFD. It was found that devices
attached to the rear of the vehicle provided the most
improved results.
Project Objectives
1. Investigate and learn from all previous work and
research for drag reduction techniques
2. Examine the results from CFD simulations of a
designated reference vehicle.
3. Design drag reduction systems with an iterative
process with a view of design optimisation
4. Perform computation fluid mechanics simulations
and analysis for drag reduction systems
5. Review drag reduction systems with
recommendations for further investigation
Project Conclusion
The aerodynamic performance of a HGV can be easily
improved with the implementation of drag reduction
systems. Devices placed at the rear face of the vehicle
obtained the best results, with a tapered device
reducing the drag coefficient by 49 drag counts. Gap
devices and underside skirtings were less effective,
however would expect a performance under cross wind
conditions.