1. Running head: DRAG REDUCTION 1
Research Proposal for Drag Analysis of Class-8 Trucks utilizing Computational Fluid Dynamics
Salman K. Rahmani
Middle Tennessee State University
Author’s Note:
If any comments or concerns arise relating to this article, please contact Salman Rahmani at 615-
351-1114 or Salmanr96@gmail.com
2. DRAG ANALYSIS 2
Introduction
Throughout the years, humans have relied heavily on energy sources that produce
harmful carbon dioxide emissions. Not only are the consumptions of these energy sources
second-nature to us, they are also detrimental to our environment and finite. With this being said,
humans have successfully explored and implemented new energy sources that are more
beneficial to our earth. A few examples of these include, Tesla’s electric powered automobile
and, China’s Three Gorges Dam which supplies electricity to millions of homes. Although our
species has found viable solutions to car emissions (like Tesla) and propane (Three Gorges
Dam), we still have not found suitable substitutes for large automobiles such as buses and semi-
trucks. One particular truck of interest is the Class 8 truck which most companies utilize for their
day to day operations such as semi-trucks and dump trucks. Some standard specifications of
Class 8 trucks include: Gross Vehicle Weight Rating of over 33,000 pounds, three or more axles
for dump trucks, and five axles for semi-trucks. With this being said, we must find an efficient
way for these vehicles to complete their day to day operations. One way to increase efficiency is
to reduce the parasitic drag that is hampering the machine. In this project, the researcher will
analyze the drag induced on the Class 8 truck trailer at different velocities through the use of
Computational Fluid Dynamics. Modifications will then be made to the trailing edge of the
trailer to reduce drag and therefore achieve higher efficiency throughout the truck’s operations.
Background
Due to the magnitude that this drag issue poses, extensive research has been invested into
this subject to try and reduce the drag’s effects on Class-8 trucks. For example, STEMCO has
developed a set of fins that attach onto the rear of the trailer that reduces the drag by trying to
providing a more seamless transition for the fluid. Another example of CFD being utilized for
3. DRAG ANALYSIS 3
drag analysis of Class 8 vehicles is Dinesh Madgundi and Anna Garrison’s discussion in regards
to how mostly 50% of the drag encountered by Class 8 vehicles is due to the trailer (Madugundi
2013). This indicates that there are significant gains to be made by making the trailer more
aerodynamic. This statement is reinforced by a study conducted by Altaf Alamaan, Omar Ashraf,
and Asrar Waqar which states that by testing various geometries of flaps at the end of the trailer,
they were able to reduce the drag by over 11% (Alamaan 2014).
Purpose
The purpose in conducting this research is to attempt and analyze the parasitic drag on
the rear of the Class 8 trailer while taking into account real world anomalies such as various
temperatures and frictional forces. To be able to conduct my research, I will be working with
ANSYS-Fluent which is a common CFD software. The expected outcome of this research is to
determine whether the modifications (rounded fillet, and rotating cylinder) implemented on the
rear of the trailer will have more of an advantageous effect over the substitutes that truck
companies are already utilizing (STEMCO’s trailing edge fins).
Methods
The method that I will utilize will be uniform throughout my whole research period. First,
the geometry rendering/creation will be constructed within Inventor. Consequently, all aspects of
the rendering will be examined and refined. The next step is to create a tetrahedral “mesh” for
the object within ANSYS Meshing. A mesh is a layer of sensors encompassing the object that
the computer uses to calculate the properties of the fluid throughout the simulation. After
creating the mesh for the object, various parameters will then be entered into ANSYS-Fluent so
that it may to take into account these factors while the simulation is active (enthalpy, fluid
4. DRAG ANALYSIS 4
properties, temperature, etc). Once all this is complete, the solution methods will then be set
(Pressure-Based Coupled Solver, RANS, Green-Gauss Node based, etc). After the simulations
are complete, the computer will be set to automatically transfer the data into an excel file so that
the results (drag, pressure, temperature, etc) can be analyzed. Once this is completed and verified
to be adequate, the process will then be repeated with the other modifications of the trailer. The
other designs include a replica of STEMCO’s fins, a rounded edge instead of a traditional L-
Shape, and a rotating cylinder on the edge. The rotating cylinders will vary in speed from
matching the fluid velocity to four times the fluid velocity. After all simulations are completed
and the data is collected, it will be reviewed to determine if a more efficient alternative to fins
have been discovered.
5. DRAG ANALYSIS 5
Timeline
The timeframe of my involvement in regards to the research will span from February 4th,
2016 to May 5th, 2016. All following dates within this timeline are estimations.
February 4th- Feb 25th
-Traditional Trailer Simulation and result harnessing
-Geometry Preparation, Meshing, Simulation
Feb 25th-March24th
-Rounded Edge (Fillet) testing
-Geometry Modification (Fillet = step height, ½ step height), Meshing, Simulation
March 24th-April 21st
-Rotational Cylinder experimentation
-Geometry Modification (Cylindrical Rotation = speed of flow, 2x speed of flow, 4x speed of
flow), Meshing, Simulation
April 21st- May 5th
-Data and result analysis
6. DRAG ANALYSIS 6
Collaboration with Mentor
Throughout the course of my research, Dr. Callender will lead the project as research
supervisor while I will be listed as the undergraduate researcher. He will provide me with
guidance along the way in case I encounter any serious issues pertaining to the research. We will
have weekly conferences in order to minimize error and increase efficiency as we proceed.
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References
Altaf, A., Omar, A.A., & Asrar, W. (2014). Passive Drag Reduction of Square Back Road
Vehicles. Journal of Wind Engineering & Industrial Aerodynamics. 134: 30-43:
Madugundi, Dinesh and Anna Garrison (2013). Class 8 Truck External Aerodynamics. Choice of
Numerical Methods, 9
Commercial Vehicles | CD-adapco. (n.d.). Retrieved January 28, 2016, from http://www.cd-
adapco.com/industries/ground-transportation/commercial-vehicles
Vanhoenacker, M. (2013, April 3). What Are Those Odd Panels on the Backs of Trucks?
Retrieved January 28, 2016, from
http://www.slate.com/blogs/browbeat/2013/04/03/truck_panels_what_do_they_do_explai
ned_photos.html
