Research Proposal for Turbulence Examination of Class-8 Vehicles
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Transcript of Research Proposal for Turbulence Examination of Class-8 Vehicles
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 [email protected]
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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.