Running head: PROPOSAL FOR FLOW CONTROL1

Proposal for Flow Control of Class-8 Vehicles with Cylindrical Modifications

Salman K. Rahmani

Middle Tennessee State University

Author’s Note:

If any questions arise regarding the information of this article, please contact Salman Rahmani at

615-351-1114 or Salmanr96@gmail.com

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Introduction

The purpose of an engine, is to provide power to propel the vehicle it is housed within.

Unfortunately, there is a fundamental force that opposes the vehicle’s motion, this force is

known as drag (Figure 1). Drag is the separation of air flow which causes a tumbling region of

air particles. This can be easily seen in Figure 2 which depicts a car followed by turbulent

airflow. The more a vehicle is aerodynamically-inefficient, the more drag it encounters. A

common aerodynamic technique to reduce drag is called streamlining. Streamlining aids the air

in sliding over and around the object. The easier the air is able to slide around the object, the less

drag force the vehicle encounters. This leads to a decrease in energy consumed from the engine

to combat drag, eventually leading to higher fuel-efficiency.

Although this solution sounds simple, one particular industry that is encountering issues

in solving this problem is long-distance product transportation, also known as trucking. The most

common truck used by trucking companies are known as Class-8 Vehicles. These vehicles must

meet standards such as: a Gross Vehicle Weight Rating of over 33,000 pounds, three or more

axles for dump trucks, and five axles for semi-trucks, and typically a trailer of fifty-three feet

(Ahanotu, 1999). Not only are these trucks extremely heavy, they are also aerodynamically

inefficient due to their large box-shaped trailer. This poses an issue in the sense that the trailers

cannot be heavily streamlined due to the fact that a decrease in volume of the trailer means a

decrease in profits for the company.

In this project, the researcher will attempt to address the issue of aerodynamics regarding

Class-8 Trucks along with their trailers. The researcher will attempt to extract the most optimal

aerodynamic design which increases fuel-efficiency whilst maintaining optimal trailer volumes.

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All of this while creating geometries which are also within the parameters of the law as set by the

transportation department.

Background

As a result of this intricate problem, billions of dollars by companies have been invested

into trying to solve this issue. In addition to company efforts, a multitude of different

independent studies have been conducted in an attempt to try and address the issue of

aerodynamics with class-8 vehicles. One such study by the National Research Council of Canada

shows that 35-55% percent of engine power for Class-8 Tractor Trailers are consumed by

Aerodynamic Losses (Patten, 2012). Another study, conducted by Dinesh Madgundi and Anna

Garrison, displayed that approximately 50% of aerodynamic drag experienced by the vehicle was

caused near the trailing edge of the trailer (Madgundi, 2013). This shows that by increasing

aerodynamic efficiency at the trailing end of the vehicle, the issue of harmful emissions may also

be addressed by reducing energy consumption within the engine.

Three studies depict that drag reduction on box-shaped objects are possible using various

geometries. The first examination that shows this is Nicodemus Myhre’s investigation into Drag

Reduction Methods for a Rearward Facing Step. Mr. Myhre showed that by modifying the

trailing edge of a 2-Dimensional rectangle shaped geometry, drag reduction is possible by up to

20% with various modifications to the trailing edge such as flaps and filleting of the edge (Myhre

2016). Altaf Alamaan, Omar Ashraf, and Asrar Waqar’s examination into Passive Drag

Reduction of Square Back Road Vehicles state that by testing various flap geometries at the end

of a 3-Dimensional trailer, they were able to achieve a maximum drag reduction of 11%

(Alamaan 2014).

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Dr. Nate Callender’s research into Optimized Lifting Line Theory Utilizing Rotating

Biquadratic Bodies of Revolution provides additional insight into the theoretical aspects of how

this issue may be addressed utilizing 3-Dimensional moving bodies. Dr. Callender displayed that

at various rotational speeds about a cylinder’s longitudinal axis (also known as alpha), a fluid’s

boundary layer is modified to the point where the turbulent region is decreased substantially

(Callender, 2013). The major breakthrough with this idea is that instead of utilizing elongated,

solid-body boundaries such as flaps to streamline a 3-Dimensional airflow, we are now able to

accomplish the same results by having rotating cylinders create the same effects. This result is

crucial in the sense that it provides information as to how fluid flow relates to rotating 3-

Dimensional bodies, a relationship that will be further investigated throughout this project.

Purpose

The purpose in carrying out this examination is to try and gain vital insight into fluid

dynamics and how its behavior upon a large 3-Dimensional object (such as a truck) is affected

based on slight modifications utilizing cylindrical geometries. The first modification that will be

examined includes two rotating cylinders (seen in yellow on Figures 3 and 4) fastened vertically

along the trailing edge of the trailer with a plate between them (seen in red). The purpose of the

cylinders is to “pull” the air over the trailing edge of the trailer whilst the plate stops the air from

creating a turbulent region between the cylinders. The second design that will be tested is four

rotating cylinders along the trailing edge of the trailer (Figures 5 and 6). This design will also

include a plate between the four cylinders. Two will be mounted horizontally (seen in green) on

the top and bottom whereas the other two will remained fastened vertically (seen in yellow).

Both of these modifications will be tested at various alphas (also known as rotational speeds).

The results from this project will not only provide us with insights needed for the advancements

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of aerodynamic concepts, but will also substantially aid in decreasing pollution output by

transportation vehicles annually.

Methods

Although full-scale experimental testing would probably be the most beneficial, its

economical demands far exceed the accommodation of an undergraduate researcher. Therefore

the method that will be utilized within this examination will be that of Computational Fluid

Dynamics. Each model of the Class-8 Truck to be tested will be rendered and created within a

Computer-Aided-Design software by the name of Inventor. Each model will then be imported

into the Fluid Dynamics Software known as ANSYS-Fluent. Here, the model will then be

outfitted with a tetrahedral “mesh” for simulation purposes (Figure 4). A mesh is an over-lay of

sensors generated by the computer by inputs from the user (size, shape, etc.) that covers the

model and records data throughout the simulations. The model (now outfitted with the mesh)

will then be moved into the simulation portion of the software in which the researcher will enter

in all of the simulation settings for the computer to use as parameters (ambient temperature,

pressure, fluid velocity, etc). Once all the above steps are completed, the simulation will begin

and the data will be recorded. Once the simulation is finished, the researcher will repeat the

process for all other designs. After testing for every model is completed, the resultant data will

then be pooled into an excel file and analyzed thoroughly by myself as well as Dr. Nate

Callender to determine whether the modifications had a positive effect on the outcome of the

drag.

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Timeline

The timeframe in which my involvement will span will be September 5th, 2016 to May 9th, 2017.

All of the following dates within the following timeline are approximations.

Sep 5th, 2016 – Sep 30th 2016

-Meshing and testing of dual cylindrical geometry at 0.5 alpha and 1.0 alpha (4

simulations each)

Oct 1st 2016 – Oct 31st, 2016

-Meshing and testing of dual cylindrical geometry at 1.5 alpha (4 simulations)

-Importing of 2.0 alpha data for dual cylindrical geometry from previous research

November 1st, 2016 – November 30th, 2016

-Re-test any dual cylindrical simulations that possessed errors

-Compile data from dual cylindrical geometry simulations and upload to spreadsheet

December 1st, 2016 – December 31st, 2016

- Finish Modeling of quad cylindrical geometry and preparation for testing

January 1st, 2017 – January 31st, 2017

-Meshing and simulating of quad cylindrical geometry 0.5 alpha and 1.0 alpha (4

simulations each)

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February 1st, 2017 – February 28th, 2017

-Meshing and simulation of quad cylindrical geometry 1.5 alpha and 2.0 alpha (4

simulations each)

March 1st, 2017 – March 31st, 2017

-Harness data from all quad cylindrical designs and upload into spreadsheet

-Search for errors within quad cylindrical simulations

April 1st, 2017 – April 30th, 2017

-Make-up any simulations that had inconsistencies or errors for quad-cylindrical

geometry

- Analysis of results from all simulations

-Prepare final report

May 1st, 2017 – May 9th, 2017

-Touch up final report and submit

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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Figure 1. (Four Forces of Flight, provided by NASA)

Figure 2. (Drag Visualization, provided by WordPress.com)

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Figure 3. (Isometric View of rendering with dual cylinders)

Figure 4. (Top View of rendering with dual cylinders and plate)

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Figure 5. (Isometric View of Current Quad Cylinder Design with plate)

Figure 6. (Top-Down View of Current Quad Cylinder Model with plate)

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Figure 7. (Isometric View of Mesh around Vehicle)

Design Mounting Position Number of Cylinders Length (ft) Radius(ft)Dual Cylinder Vertical 2 8 2Quad Cylinder Horizontal 2 4 1Quad Cylinder Vertical 2 8 1

Figure 8. (Basic Information of Vehicle Mounted cylinders)

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References

Ahanotu, D. N. (1999, July). HEAVY-DUTY VEHICLE WEIGHT AND HORSEPOEWR

DISTRIBUTION; MEASUREMENT OF CLASS-SPECIFIC TEMPORAL AND

SPATIAL VARIABILITY. Georgia Institute of Technology, 1-275. Retrieved August 31,

2016, from http://transaq.ce.gatech.edu/guensler/publications/theses/ahanotu

dissertation.pdf

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:

Callender, M. N. (2013). A Viscous Flow Analog to Prandtl's Optimized Lifting Line Theory

Utilizing Rotating Biquadratic Bodies of Revolution. Trace: Tennessee Research and

Creative Exchange, 1-92. Retrieved August 29, 2016, from

http://trace.tennessee.edu/cgi/viewcontent.cgi?article=2909&context=utk_graddiss

James, D. (Ed.). (n.d.). Atmospheric Flight. Retrieved August 31, 2016, from

http://quest.nasa.gov/aero/planetary/atmospheric/forces.html

Madugundi, Dinesh and Anna Garrison (2013). Class 8 Truck External Aerodynamics. Choice of

Numerical Methods, 9

Myhre, N. (2016, May). Computational Analysis of Drag Reduction Methods for a Rearward

Facing Step. 1-27. Retrieved August 31, 2016, from

http://jewlscholar.mtsu.edu/bitstream/handle/mtsu/4856/Myhre-Nick Thesis.pdf?

sequence=1&isAllowed=y

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Navier-Stokes Equations. (2012). Retrieved August 31, 2016, from

https://secretofflight.wordpress.com/turbulence/

Patten, J. P., McAuliffe, B., Mayda, W. P., & Tanguay, B. (2012, May 11). Review of

Aerodynamic Drag Reduction Devices for Heavy Trucks and Buses. National Research

Council Canada, 1-100. Retrieved August 29, 2016, from

https://www.tc.gc.ca/media/documents/programs/AERODYNAMICS_REPORT-

MAY_2012.pdf.