ANSYS AIM HIGH SCHOOL PROJECT GUIDEAERODYNAMICS (FLUID FLOW) & CO2 DRAGSTERSCHOOLPeters Township High School (McMurray, Pennsylvania)
INSTRUCTORChristopher Allen

CONTACTallenc@pt-sd.org

PROJECT OBJECTIVE
Design a 3D printed CO2 dragster based on predefined parameters
PROJECT OVERVIEWThis project follows the iterative design method (prototyping, testing, analyzing, and refining thedesign) to achieve minimum requirements with a primary goal of a project-based approach tovehicle design. This portion of the overall project is completed in a digital format using ANSYSAIM to test aerodynamic design. Results of the fluid-flow analysis are utilized when evaluating
vehicle body design prior to manufacturing and racing.
PROJECT STRATEGYThis project relies upon the scaffolding method in education culminating with a project-based
challenge. Prior knowledge includes parametric modeling techniques, transportation systems,
concepts of aerodynamics, additive manufacturing standards, and material science. This projectis presented to students in five phases: Research, Design and Simulation, Manufacturing andAssembly, Pre-Race Analysis, and the Race Competition.
Research Phase:​ As an introduction to this project students review current concepts relating toaerodynamics and how these concepts relate to the design of dragsters. Prior knowledge ofconcepts relating to transportation systems and individual vehicle systems.
Design and Simulation Phase:​ Students begin preliminary designs in the form of rough sketches
then move on to technical drawings based on research (​Technical Design Worksheet ​found on
page 3). This leads to the parametric modeling phase of the project and then into fluid flow
analysis of designs using ANSYS AIM. Results from the fluid flow analysis are evaluated andstudents use the data to determine changes to designs.
Manufacturing and Assembly:​ Student’s final designs are printed and assembled using thesame materials (wheels, axles, and filament material ).
Pre-Race Analysis:​ Students evaluate their manufactured CO2 dragster using a wind tunnel andand elevated ramp to complete the ​Pre-Race Analysis ​worksheet (found on page 4).

Race Competition:​ Student designs are evaluated using the ​Dragster Design Rubric ​(found onpage 5) prior to the race competition by the instructor. Students participate in a doubleelimination competition dragsters are disqualified if vehicle is destroyed during the race.

2CO2 DRAGSTERTECHNICAL DESIGN WORKSHEET

3CO2 DRAGSTER
PRE-RACE ANALYSIS
Name:
1.

Width of my car (Max 3 inches)?

2.

Height of my car (Max 2.5 inches in rear and max 1 inch in front)?

3.

Distance between front and rear axle (minimum 5 inches)?

4.

Does my CO2 chamber have holes?

5.

Did I need to fix my car with glue prior to my first race?

6.

Velocity Data (from ANSYS AIM simulation)
Calc. Max

Calc. Average

7.

Wind Tunnel Test – Place your finished car in the wind tunnel. Conduct two tests for thecoefficient of drag (CD). Test 1 should be done without a CO2 cartridge while test 2 should havea cartridge installed in the car
Coefficient of Drag (CD)
Test 1 (CD)
Lift
Test 2 (CD)
Lift
Average (CD)
Lift
Class
Best/Avg
FrFr
Fr
Rr
RrRr

8.

Ramp Test – Weigh your car prior to conducting the Ramp Test
Car Weight (CW)
Time of Travel (TT)Distance Traveled (DT)

grams
9.

sec.

Distance Off Center(DOC)in.

Calculate and Analyze Data – Based on the Ramp Test Data, calculate the ramp test accuracy,
ramp test speed, and inertia performance for the CO2 car.
Ramp Test Accuracy (RTA)
Ramp Test Speed (RTS)
Inertia Performance (IP)Use the follow equations for your calculations and show your work below
RTA = 100-(DOC/DT x 100)
RTS = DT/TT
IP = DT/CW4In.

CO2 DRAGSTERDRAGSTER DESIGN RUBRIC
107-9

4-6

1-3

Quality ofDesign

High quality design
with consideration topurpose andtransportation
theory, student
challengedhimself/herself withtheir design

Design has minor
design flawsrelating to how thecar will operate asa system, student
challenged
him/herself

Design has 1 ormore major flaws
relating to purpose
and transportation
theoryCar was designedwith noconsideration to
purpose or theory,
student put noeffort into design

Car Symmetry

Car is symmetricaland a mirror imageof itself

Car shows 1-2
minor flaws to one
side or the otherCar has more than
2 flaws to its
symmetricaldesignCar is uneven andcrooked, runs to
one side

Aerodynamic
DesignEvery face/part ofthe car was
designed to be
aerodynamic

Every face/part ofthe car was
designed to be
aerodynamic
except for 1-2

Car design lacks
aerodynamic
design in 3-4
placesCar has been
designed without
any
considerations toaerodynamics

Wheel/Axle
Quality

Wheels spin freely
with minimum
friction

Wheels spin withslight friction

Wheels spin but
only one timearoundWheels do not
spin

Quality of
Preparation

Car is sanded andfinished smooth (norough areas)

Some sanding
marks and/or
rough areas
visibleCar has roughareas withminimum sanding
effortCar has not been
sandedRace Times
Recorded

All race time
recordedMore than 1 racetime recorded but
not all race times

Only 1 race time
recorded

No race times
recorded

TOTAL POSSIBLE: 60●●SCORE:Race times should be recorded on the back of the Pre-Race Analysis sheet
Staple this sheet to your Pre-Race Analysis sheet after all of your races have been
completed5

CO2 DRAGSTERANSYS AIM AERODYNAMICS (FLUID FLOW) PROCESS GUIDE
1. Export from Inventor as a STEP Filea. File>Export>CAD Format> STEP File
2. Setup Projecta. Open ANSYS Aim and in the ​“Study” ​window select the ​“Fluid Flow” ​process

b. In the ​“Fluid Flow Template” ​window make sure that “Import existing Geometry”
is selected and click ​“Create Simulation Process” .

c. This will open a window that will allow you to select your STEP file and click“Open”.
3. Finding the Workflow window in the work area
a. In the ​center-bottom ​of the work area you will see the “​Work Flow” ​window
which shows the steps you will set up to run the simulation.
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b. First click on the ​“Geometry” ​tab, which will open the ​Geometry Process​ tab inthe ​upper-left corner ​of the screen.

c. Next click on ​“Edit Geometry” ​ so that you can add or edit required components
to the model that you will be testing.
4. Adding an enclosure to your model geometrya. After you clicked ​“Edit Geometry” ​in the last step, a model editing window willopen. The only thing you will do in this step is add an ​“Enclosure” ​ around yourmodel.

b. On the top of the toolbar click the ​“Prepare” ​tabc. In the ​Prepare tab ​ click on the “​ Enclosure” ​tool7

d. Next you will need to select what will be enclosed in the ​enclosure​ by click onthe body of your model.

e. After selecting the model to enclose, an outline of a ​rectangle​ will appear toshow where the enclosure will be oriented. Before completing this operation you
need to change the size of the rectangle by adjusting the ​cushion size.
f. On the ​left-side​ of the screen look for the ​“Create Options” ​window where you
can adjust the​ enclosure type​ and the ​cushion size​. Make sure the e​ nclosure
type​ is set to ​“Box” ​and change the ​“Default Cushion” ​to ​ 10%.

g. To complete these adjustments and add the enclosure to your model click on thegreen check box in the work area.

8h. Finally, to complete this process and return to the simulation work environment
click on the​ “Model” ​menu​ ​in the​ upper-left corner ​of the screen and click“Close”.

5. Setting up and generating the Mesha. In the ​“Workflow”​ window select the ​“Mesh” ​process

b. In the ​Mesh ​settings window on the ​left​ of the screen you will need to adjust one
error under ​Mesh Controls​.

9c.

​ lick on ​“Mesh Controls”​ and in the new ​Mesh Controls ​menu that opens clickCon ​“Inflation”

d. In the ​“Inflation”​ menu click the checkbox for ​“Automatically Defined”

e. Back in the ​Mesh Process ​window use the ​mesh resolution slider​ to adjust themesh resolution ​down to level 1 ​(as seen in the picture below)f.

In the ​Workflow menu ​there will be a ​yellow lightning bolt​ next to the ​Meshbutton, which signifies that the mesh process needs to be updated and has noother errors at this point. Click on the ​Mesh ​tab and in the ​Mesh Process ​menuclick on the ​blue lighting bolt​ to update and ​Generate​ ​Mesh.

106. The Physics Process and adding the Fluid Flow Conditions
a. In the ​Workflow ​window select the ​“Physics” p​ rocess which will open thePhysics Process ​window on the ​left of the screen.
b. First we need to change the view options so that we can see our model, which is
now inside and hidden by the model of the enclosure. ​Click on the top of you
rectangular enclosure ​ to turn it ​orange ​ and then ​right-click t​ o bring up amenu where you will click ​“Hide Face”​.

c. Next to the words ​“Fluid Flow Conditions” ​click on the ​“Add”​ button and select“Inlet”.

11d. An ​Inlet​ settings window will open on the ​left-side​ of the screen and you willneed to select where the the fluid, or in our case the air, will be entering theenclosure.
e. On your model select the wall in front of your model, which will turn it orange.

f.

Once you have the front of the enclosure selected, ​click on the plus button
over in the ​Inlet setting window​ to add that face as the inlet for your simulation.

g. Next you will need to set the ​velocity magnitude ​of this in-flow as 2​ 0 [m s^-1]​ inthe ​“Velocity Magnitude” ​box.

h. Click on the ​Physics ​tab in the ​Workflow​ window to return to the ​Physics
Settings ​window
i. Next you will set the ​Outlet ​in the same way you set the ​Inlet​ by clicking the“Add” ​button next the words ​“Fluid Flow Conditions” ​and select​ “Outlet”​.

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j.

This time​ click the back of the enclosure, opposite of the inlet, ​to set it as theexit point for the fluid, or air, in our simulation. Once you have selected thelocation for the ​outlet​ you click the ​“plus” ​button in the ​location​ box.

k.

In the ​Outlet settings​ window find the “​ Flow Specification”​ drop-down box
and set the flow specification to ​“Velocity”.

l.

In the ​“Velocity Magnitude” ​set the velocity magnitude of the outflow as ​20 [ms^-1]

m. Next, you need to set the ​walls​ of the enclosure by returning to the ​physics
settings​ window. Click the ​“Add” b​ utton next the words ​“Fluid Flow
Conditions” ​and select​ “Wall”​.

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n.

This should automatically turn everything on your model ​blue​ ​except the Inlet
and Outlet faces​, while at the same time automatically adding all of the faces tothe ​location​ box in the ​ “Wall Setting” ​window on the left of the screen.

o. Just to make sure that this included the hidden face, which we hide earlier,right-click ​on the model​ ​and select ​“Show All”​. The hidden face should also
appear blue.

7. Solve Physics
a. Return to the ​ Physics Process ​window by clicking on ​Physics ​in the ​Workflow
window.
b. Click on the blue ​“Solve Physics” ​button at the bottom of the window. Thisprocess might take up to 15 minutes to complete depending on your design.

148. Evaluate Resultsa. In the ​Workflow ​window select the ​“Results” p​ rocess which will open theResults Process ​window on the ​left of the screen.

b. Click on ​“Results”​ and the V​ elocity Process​ window will open to show asummary of your simulation.

c. Under the ​“Symbol Distribution” ​ drop-down box, change the option to ​“Basedon Mesh”​ . Then under the ​“At every Nth element”​ box change the number toa value of 150, you may also experiment with this number to get better results butany number above 1000 will slow down you computer. After you have make youradjustments you will need to click on the ​“Evaluate Results”​ again.

15

d. In the center of the work area you will see a play and button which, whenpressed, will play your simulation.

9. Evaluate Resultsa. With your simulation running, navigate around the and look for areas of yourdesign that show areas of ​dark blue arrows​, which are areas of the lowest
velocity and where your design has the most drag.
b. Arrows that are warmer colors, yellows to reds, show where your design has theleast amount of drag. Cooler colors, dark blues to light blues and greens, show
the areas with the most drag (see examples below).

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10. Document Resultsa. Following your evaluation from the last step, find and document areas of yourdesign showing the following results:i.
1 image showing your ​full side viewii.
1 image showing a ​top-down​ ​viewiii.
2 images showing areas of the ​most dragiv.
2 images showing areas of the​ least dragv.
2 images showing areas with arrows flowing in the ​negative direction

b. To save the required above pictures use the next step (Step 11) to learn how tosave the pictures.
11. Save Image of your testa. Right-Click ​on your design and then click ​“Save Image As…”

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b. In the ​“Save Image As” ​box that opens click on the button to the right of the“File” ​box that has ​3 dots​ and select your H​ : Drive​ to save each picture

c. Open and print out your pictures making sure to write on them what of therequired pictures in ​Step 10 ​(also seen below) is showni.
1 image showing your ​full side viewii.
1 image showing a ​top-down​ ​viewiii.
2 images showing areas of the ​most dragiv.
2 images showing areas of the​ least dragv.
2 images showing areas with arrows flowing in the ​negative direction

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