Final Presentation
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NASCARNASCAR AerodynamicsAerodynamics
BY: Mark AngeloniBY: Mark Angeloni
Brendon KeinathBrendon Keinath
Todd SifleetTodd Sifleet
Why Does it Matter?Why Does it Matter?
At high speed At high speed aerodynamic effects play aerodynamic effects play an enormous role in car an enormous role in car performance.performance.
By taking advantage of By taking advantage of the effects of lift the effects of lift racecars have been able racecars have been able increase their corning increase their corning ability, which in turn ability, which in turn decreases lap time. decreases lap time.
Also by minimizing drag Also by minimizing drag they can maximize the they can maximize the top speed of the car. top speed of the car.
Source: Race Car Aerodynamics, J. Katz, 1995
Model Testing in a Wind Model Testing in a Wind TunnelTunnel
We used a 1/12 scale We used a 1/12 scale model of a NASCAR, model of a NASCAR, because full-scale because full-scale prototype testing is prototype testing is more expensive and more expensive and time consuming time consuming
By running the model By running the model in wind tunnel at in wind tunnel at different velocities we different velocities we are able to model are able to model different actual car different actual car velocities, gathering velocities, gathering relevant information relevant information concerning concerning aerodynamics. aerodynamics. Source: Union College
Model TestingModel Testing
Problems With Model TestingProblems With Model Testing Not possible to match Reynolds NumberNot possible to match Reynolds Number Wind Tunnel cannot reach necessary speedsWind Tunnel cannot reach necessary speeds If it could, Mach number would be too large and we’d If it could, Mach number would be too large and we’d
have to worry about compressibilityhave to worry about compressibility Some ways to fix this problem are:Some ways to fix this problem are:
A larger wind tunnel with larger modelsA larger wind tunnel with larger models A different testing fluid with a higher densityA different testing fluid with a higher density Pressurizing and/or adjusting the air temp in the wind Pressurizing and/or adjusting the air temp in the wind
tunneltunnel Or in our case running the wind tunnel at several Or in our case running the wind tunnel at several
velocities and extrapolating to determine useful velocities and extrapolating to determine useful information.information.
The ExperimentsThe Experiments
Week 1- Surface Pressure Week 1- Surface Pressure measurementsmeasurements
Week 2- Lift and Drag measurementsWeek 2- Lift and Drag measurements
Week 3- Particle Image Velocimetry, Week 3- Particle Image Velocimetry, CFD analysisCFD analysis
Surface Pressure Surface Pressure MeasurmentsMeasurments
We used a model outfitted We used a model outfitted with 17 pressure taps to with 17 pressure taps to take pressure take pressure measurements at different measurements at different point. point.
We measured the pressure We measured the pressure at 2 different velocities 31 at 2 different velocities 31 mph, and 51.5 mph.mph, and 51.5 mph.
Using these pressures we Using these pressures we calculated pressure calculated pressure coefficients at different coefficients at different points of the model. points of the model.
Using CUsing Cpp we can calculate we can calculate pressures at any given pressures at any given point on the actual point on the actual NASCAR.NASCAR.
)21(
)(
2V
ppC p
Results - PressureResults - Pressure
Coefficient of PressureCoefficient of Pressure
Lift and DragLift and Drag
The model, was connected The model, was connected to a dynamometer that to a dynamometer that measured force in both the measured force in both the x and y direction, x and y direction, essentially lift and drag. essentially lift and drag.
This data was collected This data was collected using a data acquisition using a data acquisition system as well, and system as well, and processed with a PC. processed with a PC.
Using these measurements Using these measurements it was possible to calculate it was possible to calculate lift and drag on the car, as lift and drag on the car, as well as lift and drag well as lift and drag coefficients. coefficients.
Source: Brad Bruno
)21(
)21(
2
2
AV
FC
AV
FC
DD
LL
Results – LiftResults – Lift
Shows the Coefficient of Lift compared to the Reynolds Number of the experiment
Coefficient of Lift vs. Reynolds Number
-0.06
-0.04
-0.02
0.00
0.02
0.04
0.06
0.08
100000 120000 140000 160000 180000 200000 220000 240000 260000
Reynolds Number
Co
effi
cien
t o
f L
ift
Results - DragResults - Drag
Displays the coefficient of drag on the car compared to the Reynolds Number of the Experiment.
Coefficient of Drag vs Reynolds Number
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
100000 120000 140000 160000 180000 200000 220000 240000 260000
Reynolds Number (width)
Co
effi
cien
t o
f D
rag
Particle Image VelocimetryParticle Image Velocimetry
PIV uses the wind tunnel PIV uses the wind tunnel along with a double along with a double pulsed laser technique to pulsed laser technique to measure instantaneous measure instantaneous velocity and to map out velocity and to map out the flow field.the flow field.
This provides a visual This provides a visual representation of the flow representation of the flow along the vehicle, along the vehicle, streamlines and a streamlines and a qualitative representation qualitative representation of the velocities. of the velocities.
Source: Brad Bruno
Results - PIVResults - PIV
Flood Contour of Ford NASCAR
Streamline Contour of Ford NASCAR
Results - PIVResults - PIV
Zoomed In view of back end of NASCAR
Zoomed in view of front end of NASCAR
Computational Fluid Computational Fluid DynamicsDynamics
CFD is a mathematical CFD is a mathematical approach to modeling approach to modeling the flow around a the flow around a vehicle. It uses an vehicle. It uses an advanced computer advanced computer program to map the flow program to map the flow field. field.
Like PIV, CFD gives Like PIV, CFD gives qualitative qualitative representation of the representation of the velocity and pressure velocity and pressure around the vehicle. around the vehicle.
Source: Google Images
Results – CFD, VelocityResults – CFD, Velocity
CFD of velocity of flow over car
Results – CFD, PressureResults – CFD, Pressure
CFD of velocity of flow over car
CFD of pressure distribution as a result of flow over car
Results – CFD, CResults – CFD, Cpp
CFD of pressure coefficient as a result of flow over the car
Racecar ProgressionRacecar Progression
Reduction in Reduction in aerodynamic drag by aerodynamic drag by streamlining the shape streamlining the shape of the vehicleof the vehicle
Increase the down force, Increase the down force, negative lift, to increase negative lift, to increase cornering speedscornering speeds
Raw hp vs. streamliningRaw hp vs. streamlining
The Proof is in the PIVThe Proof is in the PIV The General The General
Lee has a box Lee has a box like shape like shape which results which results in a larger in a larger Drag than a Drag than a rounder shaperounder shape
Cd:Cd:Cube = 2.2Cube = 2.2Rounded Cube Rounded Cube
= 1.2= 1.2Sphere = 0.3Sphere = 0.3Triangle = 1.5Triangle = 1.5
Charger vs NASCARCharger vs NASCAR
Drag on Charger vs. NASCARDrag on Charger vs. NASCARCoefficient of Drag vs. Re
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
80000 100000 120000 140000 160000 180000 200000 220000 240000 260000 280000
Re
Co
ffie
cie
nt
of
Dra
g
NASCAR w/o spoilerCharger
Spoiler EffectSpoiler Effect
The addition of a The addition of a spoiler on the car spoiler on the car results in greater results in greater downward force (or downward force (or negative lift) which negative lift) which results in better results in better corneringcornering
The addition of a The addition of a spoiler also increases spoiler also increases the amount of drag the amount of drag on the caron the car
Source: Images.google.com
With or Without SpoilerWith or Without SpoilerCoefficient of Downforce
-0.04
-0.02
0
0.02
0.04
0.06
0.08
0.1
0.12
80000 100000 120000 140000 160000 180000 200000 220000 240000 260000 280000
Re
CL
NASCAR w/o spoilerNASCAR w/ Spoiler
Why Drivers DraftWhy Drivers Draft
Behind the car is a Behind the car is a low pressure/low low pressure/low velocity pocket velocity pocket which aids in the which aids in the reduction of drag reduction of drag on the following on the following carcar
This increases This increases efficiency and efficiency and speed for both carsspeed for both cars
DraftingDrafting
Courtesy of trickelfan.com
What we learnedWhat we learned
The strides made in streamlining designs The strides made in streamlining designs of cars aided in decreasing the drag force of cars aided in decreasing the drag force along a vehiclealong a vehicle
Spoilers create a larger down force on the Spoilers create a larger down force on the vehicle which helps in keeping the wheels vehicle which helps in keeping the wheels in solid contact with the ground at high in solid contact with the ground at high speeds and corneringspeeds and cornering
These concepts together help increase These concepts together help increase speeds and lap times which is the overall speeds and lap times which is the overall goalgoal
Is the data gathered useful?Is the data gathered useful?
At High Reynolds Numbers the At High Reynolds Numbers the Coefficient of Drag and the Coefficient of Drag and the Coefficient of Lift level offCoefficient of Lift level off
We are in the transition areaWe are in the transition areaThe trends of our data do not quite The trends of our data do not quite
level off so we can approximate the level off so we can approximate the actual coefficients but can’t exactly actual coefficients but can’t exactly place themplace them