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

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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

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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

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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.

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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-March 24th

-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

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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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Figures

Fig 1. Rearward Facing Step (AdaptCo)

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Fig 2. Comparison of Fins to RFS (Vanhoenacker)

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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